Consolidated Index (A-Z)

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A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z

A

ABC model of the control of flowering
ABC transporter
ABL gene
ABO blood groups
ABP1 (Auxin-binding protein 1)
Abscisic acid (ABA)
Abscission
Absorption spectrum
Abyssal plain
ACE inhibitors
Acetylcholine
[at neuromuscular junction]
Acetyl-CoA
Acid
Acid rain
Acrosome
ACTH (adrenocorticotropic hormone)
Actin filaments
[Discussion] [in cytokinesis] [in skeletal muscle]
Actinomycetes
Action potential
[in muscle fiber]
Action spectrum
Active transport
Activins
[in embryonic development] [sex hormones]
Acute lymphoblastic leukemia (ALL)
Adaptation
[of sense receptors] [evolutionary]
Adaptive radiation
Addison's disease
Adenine
Adeno-associated virus (AAV).
as vector for somatic gene therapy
Adenomatous Polyposis Coli (APC) gene
Adenosine deaminase (ADA)
and severe combined immunodeficiency (SCID)
Adenosine triphosphate (ATP)
Adenoviruses
Adenylyl cyclase
[and odorant receptors]
ADH, the antidiuretic hormone (also known as vasopressin
Adherens junctions
Adhesion
Force of attraction between unlike molecules.
Adipose tissue (fat)
[secretion of leptin by]
Adjuvant
Adrenal glands, hormones of
Adrenaline
Adrenocorticotropic hormone (ACTH)
Advanced waste treatment
Adventitious root
Aequorin
Aerobic
Requiring the presence of free oxygen.
Affinity
Strength of binding by noncovalent interactions between one site on a molecule and a monovalent ligand. [antibody affinity] [affinity maturation]
Afrotheria
AGAMOUS (AG)
Agent Orange
Aging
Agnatha
Agonist
Drug that mimics the action of another. [Example]
Agrobacterium tumefaciens
AID (Activation-Induced cytidine Deaminase)
AIDS (Acquired Immune Deficiency Syndrome)
Air
[composition of] [pollution]
AIRE (autoimmune regulator gene)
Alanine
Alcohols
Aldehydes
Aldosterone
Algae
[Brown] [Green] [Golden] [Red] [culture medium for]
Alkylation
Addition of a carbon-containing group, such as a methyl or ethyl group, to another molecule.
Allantois
Allele
Alternative version of a gene. [in Mendel's peas] [in a three-point cross] [RFLPs] [hemoglobin beta chain] [and protein polymorphisms]
Allergen
An antigen that provokes an allergic response.
Allergy
Allograft
Allopatric speciation
Allosteric
Refers to a change in the properties (usually including shape) of a protein following the binding of another molecule to the protein. [Example]
Allozyme
Alpha1-Antitrypsin
[deficiency ] [synthesis by transgenic sheep] [and emphysema]
Alpha helix
Alpha motor neurons
Alport's syndrome
Alternation of generations
[Discussion] [in ferns] [in mosses]
Alternative splicing
Alu element
Aluminum
Alvarez, L.
Alveolates
Alveoli
Alzheimer's disease
Ames Test
Amfor gene
Amides
Amines
Amino acids
Aminoglycosides
Aminopeptidase
Amino terminal
Ammonia
[in nitrogen cycle] [in urea cycle]
Amniocentesis
Amnion
[in humans]
Amniota
AMPA receptors
Amphetamines
Amphibians
Amphineura
Amphioxus
Amphiphilic
Used to describe molecules containing both polar (hydrophilic) and apolar (hydrophobic) groups. Sodium stearate (a soap) is amphiphilic.
Amygdala
Amylase
[pancreatic amylase]
Amylin
Amyloid
Amylopectin
Amylose
Anabolic steroid
Anabolism
Anaerobic
Not requiring the presence of free oxygen.
Analgesics
Analogous
Of structures (e.g., molecules, organs) in different species having similar function(s) but inherited from different precursors.
Anammox (anaerobic ammonia oxidation)
Anaphase
[in mitosis] [in meiosis]
Anaphase-Promoting Complex/Cyclosome (APC/C)
Anaphylaxis
[local] [systemic]
Androgen
Anemia
[immune hemolytic] [pernicious] [sickle-cell]
Anesthetic
Aneuploid
Having one or more extra (or fewer) chromosomes than the normal diploid (2n) set (e.g., 2n+1, 2n-1). [trisomy 21] [X chromosomes]
Angelman syndrome
Angiogenesis
Angiosperms
[life cycle] [evolutionary relationships]
Angiotensin
Angiotensin converting enzyme (ACE)
Angstrom (Å)
Animal
[cells] [invertebrate] [tissues] [vertebrate]
Aniridia gene
Annelida
ANP (atrial natriuretic peptide)
Antennapedia (Antp)
[encoded homeodomain]
Antenna pigments
Anther
Antheridia
[in ferns] [in mosses]
Anthozoa
Anthrax
[how its toxin works]
Antibiotics
Antibody
[structures] [classes] [how their diversity is created] [affinity] [binding to antigen] [monoclonal] [specificity]
Anticodon
Antidepressant drugs
Antidiuretic hormone (ADH)
Antigen
Antigenic determinant
A part of an antigen to which the antibody binds. Also called an epitope. [View]
Antigenic drift of influenza viruses
Antigen presentation
Antigen-Presenting Cells (APCs)
Antigen receptors on B and T cells
Antimicrobial peptides
Antioxidants
Antiport pump.
Antisense strand
The strand of DNA used as the template for synthesizing RNA. (Sometimes called the Watson strand.) [View] [Antisense oligonucleotides] [Antisense RNA]
Antiserum
Serum containing induced antibodies. [Example]
Antithrombin III
Antithymocyte globulin (ATG)
Antitoxin
Aorta
APC gene
APETALA
Apical dominance
Apicomplexa
Apicoplast
Apis mellifera, the honeybee
[life history] [communication]
Aplysia
Apolipoprotein B
[and cholesterol metabolism] [and RNA editing]
Apomixis
Apomorphic
Apoplast
Apoptosis
Programmed cell death. [Discussion]
Aposematic coloration
Appetite, control of
Aquaporin
Aqueous humor
Arabidopsis thaliana
Arachidonic acid
Arachnida
Archaea
Archegonia
[in ferns] [in mosses]
Archenteron
ARF1 (Auxin response factor 1)
Arginine
[substrate for NO synthases]
Arrestins
Arteries and Arterioles
Arteriosclerosis
Arthropods
Ascidians
Ascomycetes
Ascorbic acid (vitamin C)
Ascus
Asexual reproduction
Asparagine
Aspartic acid
Assisted Reproductive Technology (ART)
Association constant (K)
Assortative mating
Asthma
Astrocytes
Ataxia telangiectasia
[ATM gene] [and aging]
Atherosclerosis
[and cholesterol]
Atom
Atomic number
Atomic weight unit
One-twelfth the weight of an atom of carbon-12. Also called the dalton. [More]
Atopy
ATP (adenosine triphosphate)
[structure] [yield in cellular respiration]
ATP-binding cassette
ATP synthase
[in photosynthesis] [in mitochondria]
Atrial natriuretic peptide (ANP)
Atrio-ventricular (A-V) node
Atrium
Australopithecus afarensis
Autocrine
Refers to the influence on a cell of molecules synthesized by the same cell. [More]
Autoimmune disease
Disease characterized by the mounting of an immune response against constituents of an individual's own tissues. Some examples: [Goodpasture's Syndrome] [Type 1 diabetes mellitus] [Immune hemolytic anemia] [Immune thrombocytopenic purpura] [Myasthenia gravis (MG)] [Multiple sclerosis (MS)] [Rheumatoid arthritis] [Systemic lupus erythematosus (SLE)] [Thyrotoxicosis (Graves' disease)]
Autonomic nervous system
Autophagy
Autoradiography
Autosome
Any chromosome that is not a sex chromosome.
Autotrophic
Capable of synthesizing organic molecules from inorganic raw materials.
Auxin
[actions] [and tropisms] [differential action on roots and shoots]
Avena test
Avery, O. T.
Avogadro's number
Axial element
Axon
[axon hillock]
Azathioprine
AZT
Azidodeoxythymidine. Also called zidovudine.

B

B7
Refers to 2 similar transmembrane molecules (B7.1 & B7.2) that are expressed at the surface of antigen-presenting cells. B7.1 is also known as CD80; B7.2 as CD86. [View]
Bacillus
[anthracis] [subtilis] [thuringiensis]
Bacteria
[Descriptions of the "true" bacteria (Eubacteria)]
Bacteriophage
Virus that infects bacteria. [lambda] [phiX174 (φX174)] [T2] [T4]
Bacteroidetes
Balanced polymorphism
Barbiturate
Barcoding
Barr body
Base
Molecule or ion that can take a proton from an acid. [Discussion]
Base Excision Repair (BER) of DNA
Base pairing of DNA
Basidiomycetes
Basophil
Bats
[echo location in] [vampire]
Bax
B cell
A lymphocyte that synthesizes antibodies. Antibody-secreting cells, called plasma cells, are derived from B cells. [Discussion] [interaction with helper T cells] [how antibody diversity is generated]
BCL-2
[Role in apoptosis]
BCR
(the oncogene)
BCR
B-cell receptor for antigen [Discussion] [how its diversity is generated]
Beadle, G. W.
Behavior
[Innate] [Learned] [Group]
Benthos
Benzer, S.
Benzodiazepines
Beta-carotene
Beta conformation (in protein)
Beta-galactosidase
An enzyme (e.g., "lactase") that hydrolyzes the disaccharide lactose and related molecules. [synthesis by Z gene of lac operon]
Beta-2 microglobulin
bicoid (bcd)
Drosophila selector gene. [encoded homeodomain] [in segmentation] [role in forming the head]
Bilaterians
Bile acids
Bioassay
Quantitative determination of the concentration of a biologically active substance from its effect on a living tissue. [Example]
Biochemical oxygen demand (BOD)
Bioluminescence
Biological Control of Pests
Biomagnification, of pesticides
Biomass
The total amount of living matter in a given population or community.
Biomes
Biosphere
The part of our planet in which life exists and with which it exchanges materials. Includes a small part of the lithosphere (the solid earth) and large parts of the hydrosphere (water) and atmosphere.
Biotin
Bipolar cells of human retina
Birds
Birth control
Birth, human
Biston betularia
Bivalent
Bivalvia
Blastema
Blastocyst
The blastula formed by placental mammals. The blastocyst is the embryonic stage that implants in the wall of the uterus. [human]
Blastula
Early stage of animal development in which a single (usually) layer of cells surrounds a fluid-filled cavity (the blastocoel), thus forming a hollow ball. [frog]
Blind spot on human retina
Blood
[general discussion] [clotting] [blood groups] [blood pressure]
Blood-brain barrier
Blue-green algae (Cyanobacteria)
Bmal1 gene
BNP (brain natriuretic peptide)
Bond energy
Bonds
[covalent] [ionic] [polar covalent] [noncovalent]
Bone
Bone marrow
[transplants of]
Bone Morphogenetic Proteins (BMPs)
[in embryonic development]
Botany
The study of plants.
Bovine spongiform encephalopathy (BSE)
Boysen-Jensen
Bradykinin
BRAF
Brain, human
Branchial grooves
Brassinosteroids
BRCA1 and BRCA2
Breathing
[control of] [in insects]
Bristol's Medium
Bromodeoxyuridine (BrdU)
Bruton's tyrosine kinase (Btk)
Bryophyta
Bt (Bacillus thuringiensis)
Budding
Asexual reproduction in which a new organism develops from an outgrowth of a single parent. [Example]
Burkitt's lymphoma

C

C4 plants
Cadherins
Caenorhabditis elegans
[ general discussion ] [genome] [germline vs somatic cells] [measuring mutation rate in] [evolutionary advantage of outcrossing in]
Calciferol
Calcineurin (calcium-calmodulin-dependent phosphatase)
Calcitonin
Calcitriol
Calcium
[in nutrition] [homeostatic regulation of] [as "intracellular messenger"]
Calcium-calmodulin-dependent kinase II (CaMKII)
Calorie
The amount of heat required to raise the temperature of 1 g of water 1 degree Celsius. When capitalized, a unit of heat 1000 times larger than the above.
Calorie Restriction (CR)
Calvin cycle
Cambium
[in stems] [in roots]
Cambrian period
CaMKII
Calcium-calmodulin-dependent kinase II
CAM plants
cAMP Response Element Binding (CREB) protein
Cancer
Any disease characterized by an uncontrolled proliferation of one kind of cell. [General discussion] [Chemotherapy] [Immunotherapy] [Chronic Myelogenous Leukemia][Cancer Cells in Culture] [Burkitt's Lymphoma] [lung cancer] [colon cancer] [Oncogenes] [tumor suppressor genes] [and apoptosis] [estimating risk] [caused by power lines?] [and telomeres] ["The Causes and Prevention of Cancer" by Bruce Ames]
Capillaries
Capping of pre-mRNA
Capsaicin
Carbamates
Carbohydrates
Carbon cycle
Carbon dioxide
[in cellular respiration] [in photosynthesis] [control of breathing] [control of heartbeat] [transport by blood]
Carbonic anhydrase
Carbonyl group
Carboxylic acids
Carboxyl terminal
Carboxypeptidase
Carcinogen
A substance that causes cancer.
Carcinoma
A cancer of epithelial cells.
Cardiac (heart) muscle
Carotenoid
Carpel
Carrying capacity (K) of the environment
Cartilage
Cartilaginous fishes (Chondrichthyes)
Casparian strip
Caspase
Catabolism
Catabolite activator protein (CAP)
Catalase
Catalyst
Substance that accelerates the rate of chemical reaction without being used up in the process. Enzymes are catalysts.
Cataracts
Catecholamines
Catenins
[in adherens junctions] [as transcription factors]
Cathelicidins
CCK (Cholecystokinin)
CCR3 (CC chemokine Receptor 3)
CCR5 (CC chemokine Receptor 5)
CD ("cluster of differentiation") molecules
[CD1] [CD3] [CD4] [CD8] [CD19] [CD20] [CD22] [CD25] [CD28] [CD33] [CD34] [CD47] [CD52] [CD80 (= B7-1)] [CD86 (= B7-2)] [CD95]
cDNA
DNA produced in vitro by the reverse transcription of a messenger RNA
Cell-mediated immunity
Cells
[Animal cells] [Plant cells] [Cell Cycle] [Cell Junctions] [Cell membranes] [Cell signaling]
Cellular respiration
[Discussion] [energy relationships in]
Cellulose
Cenozoic era
Centimorgan (cM)
Central dogma
Central nervous system (CNS), human
Centriole
Centromere
Centrosome
[general discussion] [in mitosis]
Cephalopoda
Cephalosporins
Cercariae
Cerebellum
Cerebrospinal fluid (CSF)
Cestoda
[pig and fish tapeworm life cycles]
Chaparral
Chaperones and chaperonins
[in protein folding] [in protein kinesis]
Character Displacement
Chargaff's rule
Chase, Martha
Checkpoints
in the cell cycle
Chelicerata
Chemiosmosis
[in chloroplasts] [in mitochondria] [laboratory demonstration]
Chemoautotrophic
Autotrophic, using energy secured by oxidizing some inorganic substance. Characteristic of certain bacteria and archaeons.
Chemokine
A cytokine that attracts white blood cells (WBCs). These secreted proteins regulate the migration of WBCs from the blood into the tissues and promote inflammation. Some are also essential for proper embryonic development. Over 40 different chemokines have been identified. [some examples]
Chemotaxis
Chemotherapy
Treating a patient with chemicals to combat an infectious disease or cancer. [drugs used in cancer chemotherapy]
Chernobyl
[radiation] [effect of fallout]
Chiasma
Chimera
Chimpanzee
[genome] [evolutionary relationships] [learned behavior] [immunodeficiency virus (SIV)]
Chitin
[inhibitors as insecticides]
Chlamydia
Chlamydomonas
Chloracne
Chlorinated hydrocarbons, as insecticides
Chlorination of water supplies
Chlorofluorohydrocarbons (CFCs) and ozone layer
Chlorophyll
Chloroplasts
[structure] [chemiosmosis in] [genome]
Choanoflagellates
Cholecystokinin (CCK)
Cholera
[the cause] [1991 epidemic]
Cholesterol
[uptake by cells]
Cholinesterase
Chondrichthyes (cartilaginous fishes)
Chondroitin sulfate
Chordata
Invertebrate chordates
Chordin
Chorion
Chorionic gonadotropin
Chorionic villus sampling (CVS)
Choroid coat
Chromatid
Chromatin
Chromatin Immunoprecipitation (ChIP)
Chromatography
[affinity chromatography] [exclusion chromatography] [paper]
Chromatophores
Chromosomes
[discussion] [chromosome maps] [chromosome painting] [harlequin] [sex chromosomes]
Chronic granulomatous disease (CGD)
Chronic myelogenous leukemia (CML)
[discussion] [mutation]
Chronic obstructive pulmonary disease (COPD)
Chrysophyta (golden algae}
Chymotrypsin
Cigarettes and health
Cilia
Ciliates
Ciona intestinalis
Cipro®
Circadian
Occurring approximately once a day. [Discussion of circadian rhythms in Drosophila and mammals]
Circulatory system
[human: structure and function] [fish, squid, frog, lizard] ["open"]
Cistron
Citric acid cycle
Citrulline
Cladistics
Cleavage
[in frog]
Cline
Clinical studies
clinical trials of drugs
Cloaca
Posterior part of the alimentary canal into which the urinary and reproductive tracts empty in birds, reptiles, amphibians, monotremes, and many fishes. [View]
Clock (clk) gene
Clonal selection in the immune system
Clone
The descendants produced asexually from a single cell or organism. Characterized by a identical genetic constitution. [cloning DNA] [cloning animals]
Clonus
Clostridia
Clotting (coagulation) of blood
Cnidaria
Cocaine
Cochlea
Cockayne's syndrome
Codominance
The independent expression of each of two alleles in a heterozygote.
Codon
[DNA codons] [RNA codons] [mRNA translation] [exceptions to the code]
Coelacanth
Coelom
Main body cavity of many animals. It is lined with an epithelium derived from mesoderm.
Coenzyme
Cohesin
Cohesion
Force of attraction between like molecules.
Cold receptors
Coleoptile
Collagen
Collective dose
Collenchyma
Color blindness
Colostrum
Commensalism
Community
The population of plants, animals, and microbes found in a particular area and often interacting with one another.
Companion cell
Competition
[intraspecific] [interspecific]
Competitive inhibition
of enzymes
Complementarity Determining Regions (CDRs)
Complementary DNA (cDNA)
A DNA molecule synthesized (by reverse transcriptase) from an RNA template. When the template is messenger RNA (mRNA), the cDNA represents an intronless gene.
Complementation, genetic
Complement system
Compound
Compound eye, of arthropods
Computed tomography (CT)
Concepts
Condensin
Conditioned Response
Conditioning, instrumental or operant
Cones
of human retina
Confidence limits
Conidia
Conifers
Conjugation
[bacterial conjugation] [in Paramecium]
Connective tissue
Connexins
Consumer
(primary, secondary, etc.)
Contact sensitivity
[a case study] [contact dermatitis]
Contig
A DNA sequence assembled by matching overlaps of individual DNA fragment sequences. [View]
Continental drift
Contraception
Contraceptive, oral
Convergent evolution
COPI and COPII (Coat proteins I and II)
Corepressor
Cornea
Coronary system
Corpora allata
Corpus luteum
Cortex
The outer part of an organ.
Corticotropin-releasing hormone (CRH)
Cortisol
Corynebacteria
Cottony cushion scale insect
Cotyledon
Countercurrent exchangers
Covalent bond
Cowpox
COX
Initials used for two entirely different molecules: cytochrome c oxidase and cyclooxygenase
CpG islands
Cranial nerves
Craniata
Creatine phosphate
Creighton, Harriet
Cre/loxP
Crenarchaeota
Creutzfeldt-Jakob disease (CJD)
Crick, F.
CRISPR loci (clustered regularly interspaced short palindromic repeats)
Cristae in mitochondria
Crossing over
[in meiosis] [molecular mechanism]
Crustacea
Cryptochrome
[and circadian rhythms] [and germination] [and etiolation] [and photoperiodism in plants]
Cryptomonads
csd ("complementary sex determiner") gene
C terminal
Cushing's syndrome
C value
[C-value paradox]
CXCR4
Cyanobacteria
Cycle (cyc) gene
Cyclic ADP ribose
Cyclic AMP (cAMP)
Cyclic GMP (cGMP)
Cyclic photophosphorylation
Cyclin
Cyclooxygenase (COX-1 and COX-2)
[COX-2 inhibitors] [and pain]
Cyclosporine
Cysteine
Cysticercosis
Cystic fibrosis (CF)
[mutations]
Cytidine deaminase
Cytochrome
[in mitochondria] [in chloroplasts] [cytochrome c sequences in different species]
Cytokine
Protein secreted by a cell that signals other cells in a paracrine fashion or even itself (autocrine). The various lymphokines, chemokines, interferons, colony-stimulating factors, and tumor necrosis factors are examples. [cytokine receptors]
Cytokinesis
Cytokinins
Plant hormones.
Cytomegalovirus (CMV)
Cytoplasm
General term for all the contents of the cell outside the nucleus and within the plasma membrane.
Cytosine
Cytoskeleton
Cytosol
The fluid in which the organelles of the cytoplasm are suspended. Also called the ground substance of the cell.
Cytotoxic T lymphocyte (CTL)

D

Dalton
Unit of mass equal to one-twelfth the mass of an atom of carbon-12 and therefore close to the mass of a hydrogen atom. [More]
Danio rerio (the zebrafish)
Darwin, Charles
[Darwin's finches] [experiments on phototropism]
DDT (dichloro, diphenyl, trichloroethane)
[biomagnification of]
Deafness
Deamination
Removal of an amino group (-NH2) from a compound. [Equation]
decapentaplegic (dpp)
Decarboxylation
Removal of carbon dioxide from the carboxyl group of an organic acid. [in cellular respiration]
Decay in nutrient recycling
Defensins
Delayed-type hypersensitivity (DTH)
Deletions
[DNA] [mapping with]
Demographic transition
Denaturation
(1) Proteins: Alteration of the physical properties and three-dimensional structure by agents too mild to break the peptide bonds. [More] (2) DNA: Separation of the two strands of the double helix (sometimes called "melting"). [More]
Dendrite
Dendritic cells
Dendritic-cell vaccines
Dendrogram
See phylogenetic tree.
Denitrification
Deoxyribonucleic acid (go to DNA)
Deoxyribose
Desert biome
Desmosomes
Deuterostomes
Diabetes
[mellitus] [insipidus]
Diacylglycerol (DAG)
Diakinesis
Dialysis
[equilibrium dialysis]
Diapsids
Diastole
Diatoms
Dicer
Dicots
[stem structure]
Dieldrin
Dietary Reference Intakes (DRIs)
Differentiation
Structural and functional modification of an unspecialized cell into a specialized one.
Diffusion
Digestion
Dihybrid
Heterozygous at two different gene loci. [examples]
Dinoflagellates
Dioecious
Having female sex organs on one plant, male on another. The holly is dioecious. [and self-incompatibility]
Dioxin
[in milk]
Diphtheria
Diphyllobothrium latum
Diploid
Having two of each kind of chromosome (except for the sex chromosomes); 2n
[numbers]
Diplotene
Diptera
[anatomy]
Disaccharide
Disruptive selection
Dissociation
Separation of ions from a molecule or crystal lattice. [image]
Distal
Situated away from the place of origin or attachment.
Disulfide bridge (in proteins)
Dixon, H. H.
DNA
Polymer of deoxyribonucleotides that stores genetic information. [Structure: the Double Helix] [DNA chips] [DNA-DNA hybridization] [DNA fingerprinting] [DNA ligase] [DNA polymerase] [DNA recombination] [DNA repair] [DNA Replication] [DNA vaccines] ["Immortal" Strands] [Mitochondrial DNA (mtDNA)] [Pyrosequencing] [Recombinant DNA and Gene Cloning] [Repetitive DNA] ["Selfish" DNA] [Sequencing by the dideoxy method]
DNA polymerase
An enzyme that catalyzes the polymerization of deoxyribonucleotides to form DNA complementary to a template (either DNA or, in the case of reverse transcriptase, RNA). [More]
DNase I
Dolly
First mammal (a sheep) cloned from an adult cell. [More]
Domains, protein
Dopamine
[as hormone] [as neurotransmitter]
Dose-response relationships
Double-stranded breaks (DSBs) in DNA
Doubling times
Down syndrome (trisomy 21)
Drosophila melanogaster (with links to many subtopics)
also [diploid number] [genome size] [selector genes] [early embryonic development] [segmentation of the embryo]
Drugs
[clinical testing] [psychoactive] [proteins made by recombinant DNA technology]
Duchenne Muscular Dystrophy (DMD)
Ductus arteriosus
Duplication
[mutation]
Dyad
A chromosome and its duplicate that was synthesized during S phase, while still connected by their single shared centromere. The two chromosomes of the dyad are known as sister chromatids. The chromatids of the dyad separate at anaphase of mitosis and of meiosis II. [Diagram] [in meiosis]
Dynein
Dystrophin

E

E. coli
Escherichia coli, a bacterium found in the intestine. [genome] [aging in]
Ear, human
Ecdysone
Ecdysozoans
Echinoderms
Echolocation, in bats
Ecology
Study of the interrelationships of organisms and their environment.
Ecosystem
A community of organisms interacting with each other and with their nonliving surroundings.
Ectoderm
Ectodermin
Ectotherm
Edema
Effector
Body structure by which an organism acts. In humans the chief effectors are the muscles and glands.
Egestion
Elimination of undigested materials from the alimentary canal. [More]
Ehlers-Danlos syndrome
Elastase
[pancreatic] [neutrophil]
Elastins
Electric organs (and electroreceptors)
Electron
Electronegative
Having an affinity for electrons. [More]
Electron Transport Chain
Electrophoresis
Electroplates
Element
ELISA (Enzyme-linked immunosorbent assay)
Embryo
An animal or plant in an early stage of development from a zygote. The development of animal embryos is analyzed in 4 pages:
  1. Embryonic Development: Getting Started
  2. Organizing the Embryo: The Central Nervous System
  3. Organizing the Embryo: Segmentation
  4. Embryonic Development: Putting on the finishing touches
Embryonic stem (ES) cells
(general discussion with links to other pages)
Emphysema
Enantiomer
Encephalitozoon cuniculi
ENCODE (Encyclopedia of DNA Elements)
Endocrine
Refers to hormones. [discussion of human hormones] [table of human hormones] [insect hormones]
Endocytosis
[by B lymphocytes]
Endoderm
Endodermis
Endoplasmic reticulum (ER)
Endoreplication
Endosomes
Endosperm
Endostatin
Endosymbiont
An organism living within the body (or cell) of its symbiotic partner. [origin of mitochondria and chloroplasts]
Endotherm
An animal that maintains its body temperature with heat generated by its metabolism.
Endotoxin
End plate potential (EPP)
[More]
Energy
Capacity for doing work. [free energy]
Enhancer
Region of DNA that stimulates the initiation of the transcription of a gene. Enhancers differ from promoters in being farther away from, and either upstream (5') or downstream (3') of, the gene they influence. [Discussion]
Enkephalins
[More] [view enkephalin synapse]
Enzyme-linked immunosorbent assay (ELISA)
Enzymes
[Restriction Enzymes] [ Enzyme Kinetics]
Eosinophils
Eotaxin
Epicotyl
That portion of the shoot of a plant embryo or seedling above the node at which the cotyledons are attached. [View]
Epidemiology
Epigenetics
Epiphyseal plate
Epiphyte
Epithelia
Epitope
A part of an antigen to which an antibody binds. Also called an antigenic determinant. [View]
Epstein-Barr virus (EBV)
[genome] [and apoptosis] [how it evades cell-mediated immunity]
Equilibrium
State of balance between opposing actions. [sense of equilibrium in humans] [equilibrium dialysis]
Erythrocyte (red blood cell)
Erythropoietin (EPO)
[the hormone] [and somatic gene therapy]
Escherichia coli
[genome]
Esters
Estrogen
Ethers
Ethylene (as plant hormone)
Etiolation
Euarchontoglires
Eubacteria
Euchromatin
Eugenics
The application of genetics in an attempt to "improve" the hereditary qualities of humans.
Euglenozoa
Eukaryote
An organism whose cells contain a membrane-enclosed nucleus and usually other membrane-enclosed organelles such as mitochondria and plastids. Includes all living things except the bacteria and archaeons. Sometimes spelled eucaryote.
Euryarchaeota
Eustachian tube
Eutheria (placental mammals)
Eutrophication
even-skipped (eve)
[role in Drosophila embryo]
Evolution
[and adaptation] [and speciation] [convergent] [and mutations] [and development ("Evo-Devo")]
Excitatory postsynaptic potential (EPSP)
Excretion
Elimination of metabolic wastes by an organism. [in humans] [in other vertebrates]
Exocrine
Refers to glands that deposit their secretion(s) into ducts that drain to the "exterior". [discussion] [view topology] Compare endocrine.
Exocytosis
Exon
Portion of a gene that is retained in the messenger RNA (mRNA) molecule. Adjacent exons are separated from each other by introns. Often exons encode one domain of a protein. The ability to shuffle exons in different combinations may — over the course of evolution — have speeded up the creation of new genes with new functions. [More]
Exosome
Term unfortunately used for two entirely-different cell structures: (1) tiny vesicles released by the cell for various types of cell-to-cell signaling [View], e.g., antigen presentation, and (2) complexes used for RNA degradation.
Exponential growth
Expressed Sequence Tags (ESTs)
Extensor
Extracellular fluid (ECF)
Extracellular matrix (ECM)
Extraembryonic membranes
Extrinsic allergic alveolitis
Eye
[of humans] [of insects] [induction of]
eyeless (ey) gene

F

Fab fragment
Facilitated diffusion
Facilitation
Factors, clotting
Fallopian tube
Farmer's lung
Farsightedness (hypermetropia)
Fas and its ligand (FasL)
[in apoptosis] [and immune privilege] Fas is also known as CD95.
Fascia
Fatal Familial Insomnia (FFI)
Fat
[nutritional requirement] [molecular structures] [with trans fatty acids] [omega-3] [adipose tissue]
Fauna
Animal life.
Fc fragment
Feedback inhibition
Fermentation
Anaerobic decomposition of an organic compound (e.g., glucose) by a living organism. [glycolysis]
Ferns
[life cycle] [evolutionary relationships]
Ferredoxin
Fertility (F) factor
Fertilization, in humans
Fetus
Unborn vertebrate after it has largely completed the development of its organ systems (in humans, after about 2 months). [circulatory system]
Fibrin
Fibroblasts
Fibronectin
Firmicutes
Fishes
[ circulatory system ]
Fission
Asexual reproduction by division of the body into two or more equal parts.
Fissure of Rolando
Fitness, evolutionary
Flagella
Flatworms (phylum Platyhelminthes)
Flexor
Flora
Plant life.
Florigen
Flow cytometry
Flower
Illustrated discussion
Flowering, genetic control of
"Flu"
Influenza. Discussion
Flukes, blood
Fluorescence
Emission of light by a substance following absorption of radiation of a different wavelength.
Fluorescence-Activated Cell Sorter (FACS)
Fluorescence in situ hybridization (FISH)
[muscle glycogen phosphorylase DNA] [bcr/abl DNA]
Fluoride
fMRI (functional Magnetic Resonance Imaging)
FoF1-ATPase
Folic acid (folacin)
[analogs used as antibiotics]
Folkman, J.
Follicle
Follicle-stimulating hormone (FSH)
Food chains and webs
Footprinting
for ("foraging") gene
Foramen ovale
fos gene
Fossil
Any remains of an organism or evidence of its presence that has been preserved in the earth.
Founder effect
Fovea
FoxP2 ("foxhead box protein P2")
FoxP3 ("foxhead box protein P3")
Fragile X syndrome
Free energy
[ and membrane transport ]
Freshwater ecosystems
Frizzled
Frog
[embryology] [ circulatory system ] [View]
Fructose
and obesity
Fruit
FSH (follicle-stimulating hormone)
Fungi

G

G1, G2, G0
[phases of cell cycle]
GABA receptors
Gage, Phineas
Galactose
Galapagos Islands
Games parasites play
Gamete
Haploid reproductive cell which, after fusion with another gamete, forms a zygote. [More]
Gametophyte
Haploid, gamete-producing stage in the life cycle of a plant. [Discussion] [in angiosperms] [in ferns] [in mosses]
Gametophytic self-incompatibility (GSI)
Gamma aminobutyric acid (GABA) Receptors
Gancyclovir (also spelled ganciclovir)
Ganglion
Small mass of nerve tissue containing the cell bodies of neurons. [sympathetic ganglia]
Ganglion cells
[of human retina] [in visual processing]
Gap junctions
Gas constant
Gas exchange
[in humans] [in other vertebrates] [in insects] [in leaves and stems]
Gastrin
Gastropoda
Gastrulation
[in frog embryo]
Gaucher's disease
G band
Gel blotting
Geminin
Gene conversion
Gene flow
Gene locus
Location of a particular gene (or one of its alleles) on a chromosome. [examples]
Gene pool
Generator potential
Genes, reporter
Gene therapy
[using retroviral vectors] [using an adeno-associated virus (AAV) vector] [using no vector]
Genetic code
Genetic drift
Genetic mosaics
Genetic testing
[sickle-cell disease] [with in vitro fertilization]
Genome
A complete haploid set of genes. [genome sizes] [The Human Genome Projects] [mitochondrial] [chloroplast]
Genotype
Genetic constitution of an individual.
Genus
A taxonomic category that includes (usually) several closely related species. Similar genera are grouped in a family. Humans (Homo sapiens) belong to the genus Homo.
Geological eras and periods
Germination
Resumption of growth of the embryo within a seed, or of a spore. [germination in seeds]
Germline
Gerstmann-Sträussler-Scheinker disease (GSS)
Ghrelin
giant (gt)
[role of gene in Drosophila segmentation]
Gibberellins
Gibbs, Josiah Willard
Gill slits
Paired openings from the pharynx to the exterior that occur in many aquatic chordates when the gill pouches open out at the branchial grooves. [View]
Girdling
Glands
[exocrine] [endocrine]
Gleevec® (also known as STI571 and imatinib mesylate)
Glia
Global warming
Glomerulus
Glucagon
Glucocorticoids
[Discussion] [receptor bound to response element]
Gluconeogenesis
Glucose
[structure] [homeostatic regulation of]
Glutamic acid
[structure] [as neurotransmitter]
Glutamine
Glycation
Glycerol
Glycine
[structure] [as neurotransmitter]
Glycogen
Glycogenolysis
Glycolysis
Glycopeptide antibiotics
Glycophorin A
Glycoproteins
Glycosidic bond
Glycosylation
Goiter
Golgi apparatus
[Discussion] [in protein kinesis]
Gonad
Organ that produces gametes, sperm in males, eggs in females. In humans, the gonads also make sex hormones.
Gonadotropin-releasing hormone (GnRH)
Gondwana
Gonorrhea
Goodpasture's syndrome
gp120
[role in death of CD4+ T cells]
G-protein-coupled receptors (GPCRs)
[odor receptors] [pheromone receptors] [peptide hormone receptors] [taste receptors] [rhodopsin] [GABAB receptors] [opiate receptors] [serotonin receptors] [Ca2+ receptor]
G proteins
Grafting (in plants)
Graft rejection
[mechanism] [preventing]
Graft-versus-host disease (GVHD)
Immune attack against the host mediated by T cells in a transplanted organ or tissue (e.g., bone marrow). [More] [still more]
Graft-versus-leukemia
Gram stain
Grana
Grant, P. and Rosemary Grant
Granulocyte
One of the three types of leukocytes (white blood cells) that contain granules in their cytoplasm. Neutrophils, eosinophils, and basophils are the granulocytes. [More]
Granulocyte colony-stimulating factor (G-CSF)
Granzymes
Grassland biome
Graves' disease
Also called thyrotoxicosis. [More]
Gravitropism
[mechanism]
Gray (Gy)
Gray crescent
Green algae
Green fluorescent protein (GFP)
Greenhouse effect
Griffith, F.
Growth
Increase in the size of an organism, resulting from an increase in its number of cells, their size, the amount of extracellular matrix, or all of these. [human growth hormone]
Guanine
Guillardia theta
Gustducin
Gymnosperms

H

HAART
Highly Active AntiRetroviral Therapy (for AIDS)
Habitat
The type of site where an organism normally lives.
Habituation
Haeckel, E.
Hair cells
Half-life
The time needed for (1) half the atoms of a radioactive substance to decay or (2) half the amount of a substance (e.g., a drug) to be metabolized or excreted.
Haltere
HAMA
human antimouse antibodies
Ham's medium
Haploid
Having only a single set of chromosomes (n) as is present in gametes. Also called monoploid.
Haplotype
Hardy-Weinberg equilibrium
Harlequin chromosomes
Haversian canal
HDL (high-density lipoprotein)
Hearing, sense of
Heart
[anatomy of human heart ] [ control of human heart ] [ fish heart ] [ frog and lizard hearts ] [ squid hearts ]
Heat receptors
Heat transport
Hedgehog signaling
HeLa cells
Helicase
Helicobacter pylori
[adaptation to stomach]
Helix-turn-helix proteins
Helper T cells
[Discussion] [Interaction with B cells]
Hemagglutinin
of influenza virus
Hematocrit
Heme
Hemidesmosomes
Hemizygous
Genes present in only one copy, not two, in an otherwise diploid cell or individual. Human males are hemizygous for most of the genes on the X chromosome.
Hemoglobin
A red, iron-containing protein that transports oxygen and carbon dioxide in the blood of vertebrates and some invertebrates. [More] [sickle-cell] [in different species]
Hemophilia
[A, B, C] [Inheritance]
Heparan sulfate
Heparin
Hepatic portal system
Hepatitis B
HER1 and HER2
Herbaceous
Nonwoody.
Herbicides
Herbivore
An animal that eats plants.
Hereditary angioedema (HAE)
Heritability
Herpesviruses
Hershey, A. D.
Hertz
Cycles per second.
Heterochromatin
Heterodimer
Complex of two different proteins.
Heteroduplex DNA
Heteroplasmy
Heterotrophic
Requiring a supply of organic compounds (food) from the environment. [ More ]
Heterozygous
Having two different alleles (e.g., A and a) at the corresponding gene loci on homologous chromosomes.
Hexapoda (the insects)
Hexose
Hippocampus
Histidine
Histocompatibility molecules
[class I] [class II] [minor] [genes that encode them] [structure of HLA-A2]
Histones
[ histone acetyltransferases (HATs) ] [ histone deacetylases (HDACs) ]
HIV, the Human Immunodeficiency Virus
[how it evades the immune system]
HLA
human leukocyte antigen [structures] [genes]
Homeobox
A sequence of 180 base pairs which encodes a 60-amino acid homeodomain found in many DNA-binding proteins. Genes containing homeoboxes are found in all eukaryotic genomes.
Homeostasis
Maintenance of a relatively constant internal environment (ECF).
Homeothermic
Having a constant body temperature above that of the usual surroundings; therefore, "warm-blooded".
Hominoid
Group of primates that includes hominids and hominins. [Discussion]
Homodimer
Complex of two identical protein molecules.
Homo habilis
Homologous
Showing a fundamental similarity of structure because they have been inherited from a common ancestor. Applied to structures ranging from organs to molecules.
[illustrated discussion] [chromosome pairs]
Homoplasmy
Homozygous
Having identical alleles (e.g., AA or aa) at the corresponding gene loci on homologous chromosomes.
Honeybees (Apis mellifera)
[life history] [honeybee communication]
Hormesis
Hormone
Substance secreted by cells in one part of the body which, after being transported by body fluids, exerts an effect on the activities of cells elsewhere in the body. [of humans] [of insects] [sex hormones] [of plants]
Horsetails
Hox gene clusters
[in Drosophila, mouse, and human]
HTLV-1
and adult T-cell leukemia/lymphoma (ATL)
Hubel, D. H.
Human Genome Project (HGP)
Human papilloma virus (HPV)
[interaction with tumor suppressor genes] [and apoptosis] [vaccine]
Humus
hunchback (hb)
[role of gene in Drosophila segmentation]
Huntington's disease
[mutation]
Hutchinson-Gilford progeria syndrome
Hyaluronic acid
Hybrid
Organism produced by genetically dissimilar parents. It is heterozygous for one or (more often) many pairs of genes.
Hybridization
Hydrocarbons
Hydrogen bond
[ in DNA ]
Hydrolysis
Decomposition of a substance by the insertion of water molecules between certain of its bonds. Food is digested by hydrolysis.
Hydronium ion
Hydrophilic
Used to describe molecules or molecular groups that are attracted to water and other polar solvents.
Hydrophobic
Used to describe molecules or molecular groups that mix poorly with water. Hydrocarbons and fats are hydrophobic. [hydrophobic interactions between macromolecules]
Hydroxyl group
Hydroxyl radical
Hypercholesterolemia, familial
Hypertension
Hypertonic solutions
Hypervariable regions
Hypocotyl
That portion of the shoot of a plant embryo or seedling below the node to which the cotyledons are attached. [View]
Hypothalamus
[hormones of]
Hypothesis
[testing] [null]
Hypotonic solutions

I

IAA (Indole-3-acetic acid)
ICAM-1 (InterCellular Adehesion Molecule-1)
I-cell disease ("inclusion-cell disease")
IgA
A class of antibody molecules abundant in tears, colostrum, and other secretions. [More]
IgE
A class of antibodies responsible for certain immediate hypersensitivities (allergies). [More]
IgG
The class of antibody molecules that is most abundant in the blood. [More]
Ilyanassa obsoleta
Imatinib mesylate (also known as Gleevec® and STI571)
Immune globulin (IG)
Immune privilege
Immune surveillance
Immune System
[anatomy] [antigen receptors] [B cells and T cells] [clonal selection] [generation of antigen receptor diversity]
Immunity
[adaptive vs. innate] [adaptive immunity in prokaryotes] [cell-mediated] [active vs. passive] [complete list of topics]
Immunological memory
Immunological synapse
Immunological tolerance
The inability to produce antibodies and/or a cell-mediated immune response to a particular antigen.
Immunosuppression
The use of drugs or other agent (e.g., x rays) to inhibit an immune response. [More]
Immunotoxin
Impact hypothesis
Implantation
Imprinting
[genomic or parental (the preferential expression of the allele inherited from one parent or the other)] [in animal behavior]
Inbreeding
Incretins
Indels
Independent assortment of genes
Indian pipe
Indole-3-acetic acid
Industrial melanism
Inflammasome
Inflammation
Influenza
Ingestion
Inhibitory postsynaptic potential (IPSP)
Inner Cell Mass
[of mouse blastocyst] [of human blastocyst]
Inorganic
Term describing all compounds that do not contain carbon as well as a few simple carbon-containing substances such as carbon dioxide and the carbonates.
Inositol-1,4,5-trisphosphate (IP3)
Insecticides
Insects
[insect hormones] [orders of]
Insertions (in DNA)
Instincts
Insulators
Insulin
Insulin-like growth factor
[Igf-1] [Imprinting of Igf-2 gene (as well as that of its receptor)]
Integral membrane proteins
Integrase
Integrins
[and angiogenesis]
Inteins
Interferon (IFN)
Interleukins
Cytokines that regulate development and activities of leukocytes. [in blood cell formation] [interactions with helper T cells]
Intermediate filaments
Intermediate host
Host normally used by a parasite during an immature or larval stage of the parasite's life cycle. [of tapeworms] [of blood flukes]
Interneuron
Interphase
Interstitial fluid
The fluid lying between, and thus bathing, the cells of animals. Interstitial fluid (also called extracellular fluid — ECF) is derived from blood. Lymph is derived from it.
Intertidal zone
Intestine
Intracytoplasmic Sperm Injection (ICSI)
Intrauterine devices (IUDs)
Intrinsic factor
Introgression
Intron
Portion of a gene that is transcribed into RNA but is removed during the formation of the mature RNA molecule. Found in rRNA and tRNA genes as well as in genes encoding proteins. Most eukaryotic genes have introns; most genes in bacteria and archaeons do not. [More] [Group I] [Group II]
Invariant (Ii) chain
Invertebrates
Inverted repeats
In vitro
Done in the "test tube".
In Vitro Fertilization (IVF)
[prior genetic screening]
In vivo
Refers to experiments performed in the living organism.
Iodine
Ion
Atom or group of atoms that has an electrical charge arising from the gain or loss of electrons.
Ion channels in cell membranes
Ionic bond
Chemical bond formed between ions of opposite charge. [More]
Iron
[nutritional requirement]
Islets of Langerhans
Isoleucine
Isomer
Molecule with the same molecular formula as another but with a different structural formula (e.g., glucose and fructose). [optical isomers]
Isometric
The contraction, without shortening, of a muscle. [More]
Isotonic
(1) Adjective to describe the contraction of a muscle that is allowed to shorten as it exerts a steady force. (2) Having the same concentration of water as the solution under comparison. (More)
Isotope
Atom that differs in weight from other atoms of the same element because of a different number of neutrons in its nucleus. [Discussion]

J

JAK-STAT pathway ["JAnus Kinase-Signal Transducer and Activator of Transcription"]
Jasmonates
Jenner, Edward
Joly, J.
jun gene
Juvenile hormone (JH)
[as insecticide]

K

Kallikrein
Kandel, E. R.
Kaposi's sarcoma herpesvirus (KSHV)
Karyotype
[of normal human male]
Keratan sulfate
Keratin
[in intermediate filaments]
Ketones
Kidney
[anatomy and physiology] [hormones of] [comparative vertebrate kidneys]
Kinase
Enzyme that attaches phosphate groups. The human genome encodes 518 different kinases that add phosphate groups to proteins. [Tyrosine kinases]
Kinesin
Kinetochore
[and mitosis] [and meiosis]
Kin Selection
Kisspeptin
Klamath weed
Klinefelter's syndrome
Klotho
Knockout mice
Krüppel gene
K-strategists
K-T boundary
Kuffler, S. W.
Ku protein (a dimer of Ku70 and Ku80)
Kuru

L

lac operon
[Discussion] [using it to detect mutations in mice] [using it to detect cell-specific gene expression]
lac repressor
[Discussion] [isolating by affinity chromatography]
Lactase
Lacteal
Lactose
Lagging strand (DNA)
Lamarck, J-B
Laminins
Lamins
Larva
Immature stage of many animals that must undergo metamorphosis to become an adult. [trochophore larva] [insect larva]
Latent period
Lateral geniculate nucleus (LGN)
[human] [in visual processing]
Laurasia
Laurasiatheria
LD50
[ of insecticides ]
LDL (low-density lipoprotein)
Leaf
[structure] [gas exchange in]
LEAFY protein
Learning
Legume
A member of a family of pod-bearing plants that includes peas, beans, clovers, alfalfa (lucerne), and so on. [and symbiotic nitrogen fixation]
Lens of human eye
Lenticels
Leptin
Leptotene
Leucine
Leukemia
A cancer characterized by the uncontrolled proliferation of a clone of leukocytes circulating in the blood. Compare with Lymphoma.
[Chronic Myelogenous Leukemia (CML)] [Chronic Lymphocytic Leukemia (CLL)] [Acute Lymphoblastic Leukemia (ALL)]
Leukocyte
Leukotrienes (LTs)
[ inhibitors for treating asthma ]
Lewis, E. B.
LFA-1 (Leukocyte Function-associated Antigen-1)
LH (Luteinizing hormone)
Licensing factors
Lichens
Liddle's syndrome
Ligaments
Ligand
A molecule that binds to another molecule or to a cell.
Light-harvesting complexes (LHCs)
Lignin
Complex substance found in the cell walls of sclerenchyma and xylem tissue, which are strengthened by it.
Limbic system
Limiting dilution analysis
Limnetic zone
LINES (Long Interspersed Elements)
Lineweaver-Burk plot
Linkage
Tendency of two genes to be inherited together because they are located on the same chromosome. [Discussion]
Lipase
Lipids
Hydrophobic organic molecules such as triglycerides (fats and oils) and some steroids. [serum lipids]
Lipopolysaccharide (LPS; also known as endotoxin)
Lipoprotein
Listeria monocytogenes
Littoral zone
Liver
[hormones of] [physiology]
Liverworts
Lizard, heart of
Locus
The position that a gene occupies in a DNA molecule or the chromosome containing that DNA. [Example]
Logistic growth curve
Long-term
depression (LTD)
facilitation
potentiation (LTP)
sensitization
Long Terminal Repeats (LTRs)
Loop of Henle
Lophotrochozoans
Lorenz, K.
Lorenzo's Oil
Loss of heterozygosity (LOH)
Lovastatin
LPS (lipopolysaccharide; also known as endotoxin)
Luciferase
Lumen
The cavity inside a tubular structure such as a blood vessel or kidney tubule.
Lung cancer
Lungs
[ human] [other vertebrates]
Luteinizing hormone (LH)
Lycopsids
Lyme disease
Lymph
Lymph nodes
Lymphocyte
[ T cells and B cells ]
Lymphoid
Referring to lymphocytes or tissues (e.g., lymph nodes) in which lymphocytes are a major constituent.
Lymphokine
Protein secreted by lymphocytes that affects their own activity and/or that of other cells. Most of the interleukins are lymphokines. Lymphokines represent a subset of cytokines. [examples]
Lymphoma
A cancer characterized by the uncontrolled proliferation of a clone of leukocytes forming solid masses in the body. Compare with Leukemia.
[Burkitt's lymphoma]
Lymphotoxin
Cytokine that triggers apoptosis. Also known as tumor necrosis factor-beta (TNF-β) [More]
Lysergic acid diethylamide (LSD)
Lysine
Lysis
The disintegration of a cell following damage to its plasma membrane. [hemolysis]
Lysogeny
Lysosomes
Lysozyme
[ structure ]

M

mab-5
C. elegans gene [see encoded homeodomain]
Macrolide antibiotics
Macromolecule
A molecule with a molecular weight of several thousand or more. Proteins, nucleic acids, cellulose, and starch are macromolecules.
Macronucleus
Macrophage
Macrophage colony-stimulating factor (M-CSF)
MAD
mitotic arrest defective
Mad cow disease
Magnetic resonance imaging (MRI)
Magnetoencephalography (MEG)
Magnetoreceptors
Magnetotaxis
Major histocompatibility complex (MHC)
A cluster of genes, some of whose products are involved in presenting antigens to T cells and also serve as the principal targets of graft rejection. Found in most, if not all, vertebrates. The MHC of humans is on chromosome 6 and is designated HLA. [diagram of the complex] [the class I and class II histocompatibility molecules]
Malaria
[Life cycle of Plasmodium vivax] [evading host immunity]
Malignant
Refers to a cell that cannot stop dividing; also to the tumor that results. Cancerous.
Maltose
Mammals
orders of placental mammals
Mandibulata
Mangold, Hilde
Marijuana
Marine ecosystems
Mars (life on?)
Marsupial
Any of the order of pouched mammals such as opossums, wombats, and kangaroos. [Discussion] [pregnancy and birth]
Mast cell
[role in allergies]
Matrix
(1) Extracellular material in which animal cells are embedded, especially those of connective tissue [More]. (2) Fluid contained within the inner membrane of mitochondria.
Maximum sustainable yield
Mayr, E.
McClintock, Barbara
[and transposons] [demonstration that genetic recombination of linked genes occurs by chromosome crossovers]
MCM proteins ("minichromosome maintenance proteins")
Mechanoreceptors
Medulla
Inner part of an organ.
Medulla oblongata
Megakaryocyte
Megaspore
Meiosis
Melanocyte-stimulating hormone (MSH)
Melanopsin
Melatonin
Membrane Attack Complex
Memory
[Implicit and Explicit] [and long-term potentiation (LTP)]
Memory cells of immune system
Mendel, G.
[his monohybrid crosses] [his second rule]
Meninges
Menopause
Menstrual cycle
Meprobamate
Meristem
[in roots] [in stems]
Merkel cells
Meselson, M. S.
Mesoderm
Mesophyll
Mesozoic era
Metabolism
Exchange of matter and energy between an organism and its environment and the transformation of this matter and energy within the organism.
[General discussion with links to specific examples] [Intermediary]
Metabolite
A substance used in or produced by metabolism.
Metabolome
Metagenomics
Metamorphosis, insect
Metaphase
[in mitosis] [in meiosis I]
Metastasis
A secondary growth of malignant (cancer) cells away from the site of the primary tumor.
Metazoa (the animals)
Methane
a greenhouse gas
Methanogens
Methionine
Methyl group
[structure] [methylation of DNA] [methylation of histones]
Michaelis-Menten constant
Micron (µ)
Micronucleus
Microorganism
An organism of microscopic size such as bacteria, protozoans, and many algae. Also called a microbe.
Micropyle
MicroRNAs (miRNAs)
Microspore
Microsporidia
Microtubules
Microvilli
Mifepristone (RU486)
Miller, Stanley
Millisievert (mSv)
Mimicry
Mineralocorticoids
Minerals
[nutritional requirements] [Recommended Dietary Allowances (RDAs)]
Miniature Inverted-repeat Transposable Elements (MITEs)
Miracidium
Mismatch repair of DNA
Mitochondrial Eve
Mitochondrial stimulation factor (MSF)
Mitochondrion
[structure and functions] [genome] [diseases]
Mitosis
Nuclear division that follows duplication of the chromosomes, whereby each daughter nucleus has exactly the same chromosome content as the parent nucleus. [Discussion] [ and cell cycle]
Mixtures
Mole
Molecular clocks
Molecular weight
Molecule
Smallest particle of a covalently bonded element or compound that retains the properties of that substance.
Mollusks
Molt
To shed the outer covering. [in insects] [disruptors as insecticides]
Monoamine oxidase (MAO) inhibitors
Monoclonal antibodies
[for treatment of cancer]
Monocots
[stem structure]
Monocyte
Monoecious
Having both female and male cones or flowers on the same plant. [More]
Monoglyceride
Glycerol carrying a single fatty acid.
Monohybrid cross
Monomer
Simple molecular unit that can be linked with others to form a polymer. The glucose molecule is the monomer of starch.
Monoplacophora
Monosaccharide
Monotremes
Egg-laying mammals (Prototheria) [Discussion]
Morgan, T. H.
Morphology
Study of structure.
Mosaics, genetic
Moss
[life cycle] [evolutionary relationships]
Motor unit
M-phase promoting factor (MPF)
MPS-I (mucopolysaccharidosis I)
Multiple alleles
More than two alleles found at a give gene locus in a population. [example in plants] [example in humans]
Multiple factors
Nonallelic genes that affect the same trait in an additive fashion. [More]
Multiple myeloma
Multiple sclerosis
[as autoimmune disease]
Murchison meteorite
Muscarinic acetylcholine receptors
Muscles
[Discussion of skeletal, cardiac, and smooth muscle] [testing the sliding-filament model of muscle contraction]
Muscle spindles
Muscular dystrophy
Mutagen
Agent that causes mutations. [Ionizing radiation] [Testing chemical mutagens in bacteria] [Testing chemical mutagens in mice]
Mutation
[general discussion] [and evolution] [germline vs somatic] [in B-cell antibody genes] [by transposons] [temperature-sensitive]
Mutualism
Myasthenia gravis
myc
[and Burkitt's lymphoma]
Mycelium
Mycobacteria
[uptake by cells] [Mycobacterium leprae genome]
Mycoplasma
[genomes of]
Mycorrhiza
Myelin sheath
Myeloid
Refers to all the blood cells except the lymphocytes.
Myeloma protein
The immunoglobulin (antibody) produced by a cancerous clone of plasma cells. [View]
Myeloperoxidase
Myofibrils
Myoneural junction (also called a neuromuscular junction)
Myosin
Myostatin
Myriapoda
Myxobacteria
Myxoma virus

N

N-acetylglucosamine (NAG)
nanos
[role of gene in Drosophila segmentation] [establishing the tail of the Drosophila embryo]
Natural Killer (NK) Cells
Natural selection
[types] [effect on gene pool]
Nearsightedness
Nekton
Nematoda
Nephron
Neritic zone
Nerve
Bundle of axons.
Nervous system
[human central nervous system (CNS)] [human peripheral nervous system (PNS)]
Net productivity
Neural folds
Neuraminidase of influenza virus
Neuromuscular junction
Neuron
A nerve cell. [Structures] [Function]
Neuropeptide Y
Neurospora crassa
Neurotransmitter
Substance released at the axon terminals of a neuron that either stimulates or inhibits the next neuron or muscle fiber. Acetylcholine and noradrenaline are neurotransmitters. [Discussion]
Neutron
Neutrophil
NF-AT ["Nuclear Factor of Activated T cells]
NF-κB ["Nuclear Factor - kappa B"]
Niacin
Nicotinic acid, one of the B vitamins.
Niche
The place in a biological community occupied by a particular species in its relation to other species.
Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP)
Coenzymes that transfer electrons within the cell. [Discussion and structure] [in Calvin cycle] [from light reactions] [NADH dehydrogenase]
Nicotinic acetylcholine receptors
Nilsson-Ehle, H.
Nitric oxide (NO)
[physiological functions]
Nitrification
Nitrogen cycle
Nitrogen fixation
The conversion of atmospheric nitrogen (N-N) into nitrogen-containing compounds like ammonia. [Discussion] [symbiotic]
Nitrogen oxides (NOx)
[and acid rain] [and photochemical smog]
NKT Cells
N-linkage
NMDA receptors
Nociceptors (pain receptors)
Nodal
Node
(1) In plants, the point on the stem at which one or more leaves develop. [diagram] (2) of Ranvier
noggin gene
Nondisjunction
Nonhomologous End-Joining (NHEJ)
Nonsense-Mediated mRNA Decay (NMD)
Noradrenaline (norepinephrine)
Northern blot
NO synthases (NOS)
Notch signaling
Notochord
[in frog embryology]
N-regions of antigen receptor genes
NSAIDs
nonsteroidal anti-inflammatory drugs (e.g., aspirin)
N-terminal
Nuclear localization sequence
Nuclear Pore Complexes (NPCs)
Nuclease
An enzyme that hydrolyzes a nucleic acid, DNA or RNA. Examples: DNase I, Ribonuclease P.
Nucleic acid
A polymer of nucleotides; DNA and RNA.
Nucleolus
Nucleoside
Nucleosomes
Nucleotide
[Antisense oligonucleotides]
Nucleotide Excision Repair (NER) of DNA
Nucleus
Nucleus accumbens
Nude Mouse
Null hypothesis
Nutrition
[requirements] [gastrointestinal (GI) tract]

O

Oceanic zone
Okazaki fragment
OKT3
[More]
Olfaction, the sense of smell
Oligonucleotide
A short polymer of, for example, 20 or so deoxyribonucleotides or ribonucleotides; thus a fragment of DNA or RNA.
Ommatidia
Oncogenes
Oncogenic
Cancer causing.
One Gene - One enzyme Theory
Ontogeny
The development of an individual organism from fertilization to maturity.
Oogenesis
Oomycetes
Ooplasmic transfer
Open Reading Frame (ORF)
DNA sequence beginning with ATG and read in triplets until it ends with a STOP codon. An ORF is potentially able to encode a polypeptide.
Operator
A DNA sequence in bacteria to which a repressor or activator protein binds, turning off (or on) transcription of the associated genes of the operon.
Operon
A set of adjacent genes and the operator that controls them. [lac operon]
Opiates
[and pain relief]
Opsin
Opsonin
Organ
Group of tissues that performs a specific function for an animal or plant (e.g., stomach, leaf).
Organelle
Specialized part of a cell (e.g., mitochondrion) analogous to an organ.
Organic
Term describing all compounds whose molecules contain carbon, with a few exceptions such as carbon dioxide and carbonates. [types and functional groups]
Organism
Individual living being.
Organizer (in frog embryology)
Organ of Corti
Organophosphates
Origin of Life
Origin Recognition Complex (ORC)
Ornithine
Orthologous genes
Homologous genes in different species; thus genes that have descended from a gene in the common ancestor of those species. Compare paralogous genes.
Osmosis
Osmotic pressure
[in guard cells of leaf] [in phloem] [in capillaries] [in kidney function] [and root pressure]
Ossicles
Osteichthyes (bony fishes)
Osteoclasts and osteoblasts
Osteogenesis imperfecta
Osteomalacia
Osteoporosis and calcium
Otoliths
Ovary
Ovulation
[role of hormones in]
Ovule
Oxidation
Process of removing electrons from a substance. [in mitochondria]
Oxygen
[transport by blood] [in cellular respiration] [in photosynthesis (More)] [in breathing] [Bond energies (More)] [Electronegativity] [Redox potential]
Oxytocin
Ozone
Highly active form of oxygen (O3 instead of O2). [ozone hole] [and photochemical smog]

P

p16INK4a
[tumor suppressor gene] [and aging]
p53
[tumor suppressor gene] [detecting DNA damage]
Pachytene
Pacinian corpuscle
Packaging cell (for retroviral gene vectors)
Pain
Paleozoic era
Palindromes
Pancreas
[hormones of] [digestive enzymes]
Pandemic
Paneth cells
Pangaea
Para-aminobenzoic acid (PABA)
Paracrine
Refers to the influence on a cell of chemical signals released by neighboring cells. Compare autocrine and endocrine.
Parainfluenza virus (PIV)
Paralogous genes
Genes in one species that have arisen by duplication of an ancestral gene. Example: genes encoding olfactory receptors. Compare orthologous genes.
Paramecium caudatum
Paraphyletic
A term in taxonomy used to describe a group of organisms sharing a common ancestor (thus members of a clade) but that excludes one or more groups within that clade. Thus the class Reptilia is a paraphyletic group because reptiles share a common ancestor with the separately-classified birds (class Aves) and mammals (class Mammalia). An example. Another example.
Parasitism
[How parasites evade host defenses]
Parasympathetic nervous system
Parathion
Parathyroid hormone (PTH)
Parenchyma
p arm
Parthenogenesis
[ and imprinting ]
Passive immunity
Patch clamp technique
Patch test (for contact dermatitis)
Pathfinder mission to Mars
Pathogen
Disease-causing organism or virus.
Pathogen-Associated Molecular Patterns (PAMPs)
Pattern Recognition Receptors (PRRs)
Pax6
P bodies
PCR (polymerase chain reaction)
Pdx-1 gene
P element
Pemphigoid and pemphigus
Penicillin
Pentose
Pepsin
Peptidase
Enzyme that hydrolyzes peptides into amino acids.
Peptide bond
Peptidoglycan
Perforin
Pericycle
Period (per) gene
Peripheral membrane protein
[Schematic (48K)]
Peripheral nervous system, human
Peroxisome-proliferator-activated receptors (PPARs)
Peroxisomes
[ peroxisomal targeting signal (PTS) ]
Peroxyacetyl nitrate (PAN)
Peroxyl (or peroxy) radical
PERV (porcine endogenous retrovirus)
Peyote
pH
[effect on enzyme action]
Phage display
Phagocytosis
Pharyngula
Phencyclidine (PCP)
Phenotype
Appearance of an organism, resulting from the interaction of its genotype and its environment.
Phenylalanine
Phenylketonuria (PKU)
Pheromones
[insect] [in mammals]
Philadelphia chromosome (Ph1)
PhiX174 (φX174)
Phloem
[function in translocation] [structure] [in roots]
Phosphatase
Enzyme that removes phosphate groups
Phosphate group
Phospholipids
Photoperiodism, in plants
Photophosphorylation
Photorespiration
Photosynthesis
[Calvin cycle] [light reactions] [energy relationships in] [history]
Photosystems I & II
Phototaxis
Phototropin
[ and phototropism ] [ and stomatal opening ]
Phototropism
Phylogenetic tree
[of hominoids]
Phylogeny
Evolutionary history of a species.
Phylum
Physiology
Study of the processes occurring in living organisms.
Phytochrome
[in etiolation] [in photoperiodism]
Pigment
Substance that absorbs light, often selectively. [antenna pigments] [absorption spectra]
Pilin
Pineal gland
Pinocytosis
PIN proteins
Pistil
PISTILLATA (PT)
Pituitary gland, hormones of
Pitx1
Placenta
[functions] [hormones] [as an allograft]
Plague
Planarian
Plankton
Plant
[cells] [growth] [kingdom] [succession] [tissues]
Plasma
Fluid matrix of the blood. [Discussion]
Plasma cell
Plasma membrane
Plasmid
Plasmin
Plasmodesmata
Plasmodium falciparum
[immune evasion]
Plasmodium vivax
Plasmolysis
Plastocyanin (PC)
Plastoquinone (PQ)
Platelets
[ and blood clotting ]
Platyhelminthes (the flatworms)
Pleiotropy
The production by a single gene of more than one effect on the phenotype.
Plesiomorphic
Plumule
Terminal bud of a plant embryo, usually consisting of embryonic leaves and the epicotyl. [Picture]
Pluripotent stem cells
Pneumococci (Streptococcus pneumoniae)
[rough and smooth] [types] [genome]
Poikilothermic
Having a body temperature that fluctuates with that of the surroundings. Commonly, "cold-blooded".
Polar body
[genetic screening of]
Poliovirus
Pollination
Polyadenylation
Polymer
Compound whose molecule consists of many repeated units linked together.
Polymerase chain reaction (PCR)
Polymorphism
Polyol
Polyp
Abnormal growth of tissue that is still benign and polyclonal. Some polyps tend in time to develop a malignant clone of cells. [in colon]
Polypeptide
[polypeptide antibiotics]
Polyploidy
Polysaccharide
Polysome
[in protein synthesis] [picture]
Polytene
Used to describe the multistranded ("giant") interphase chromosomes found in certain metabolically active cells of insects.
Polytene chromosomes
Pons
Populations
[ how regulated ] [ human ] [ cycles ]
Porifera (the sponges)
Porphyria, inheritance of
Positron-emission tomography (PET)
Post transcriptional gene silencing (PTGS)
Postzygotic isolating mechanisms
Potassium channels
involvement in hereditary deafness
Potential
[action potential] [excitatory postsynaptic potential (EPSP)]
[inhibitory postsynaptic potential (IPSP)] [resting potential]
PPM
Parts per million. [More]
Prader-Willi syndrome
Precocenes
Precursor
Substance from which another substance is formed.
Precursor activation
Predation
Living by devouring other organisms.
Pregnancy
[in humans] [hormones]
Premature termination codons (PTCs)
Pre-messenger RNA (pre-mRNA)
Prenatal Diagnosis
Pressure-Flow theory
Prezygotic isolating mechanisms
Primary host
Host normally used by a parasite during the adult stage of its life cycle.
Primary structure (Protein)
Primary transcript
Primates
Primitive
Similar to that occurring in the early evolutionary history of the structure or organism in question.
Primordial germ cells (PGCs)
Prion diseases
Producer
An organism that can synthesize organic molecules from inorganic ones (i.e., an autotroph). Producers start food chains.
Profundal zone
Progeria
Progesterone
Progestin
Any steroid that mimics the effects of progesterone.
Prokaryote
General term used for organisms that are not eukaryotes. Includes two evolutionarily-distinct groups: bacteria and archaeans. Sometimes spelled procaryote.
Prolactin (PRL)
Proline
[structure] [in collagen]
Promoter
Region of DNA, usually on the 5' side of a gene, that is needed for the initiation of the transcription of that gene. RNA polymerase and other transcription factors bind to the promoter. [bacterial promoters] [eukaryotic promoters] [part of response element]
Pronucleus
The sperm nucleus and egg nucleus within the fertilized egg before their fusion to form the diploid zygote nucleus. [in humans] [making transgenic animals]
Proopiomelanocortin (POMC)
Prophage
Prophase
[mitosis][meiosis I]
Proprioception
Prostaglandins
[role in birth] [role in allergies]
Prostate gland
Prosthetic group
The nonprotein part of a conjugated protein. Metal ions and a variety of organic molecules (e.g., vitamins, sugars, lipids) can serve as prosthetic groups. Prosthetic groups are usually bound covalently to their proteins. [More]
Protease
Enzyme that hydrolyzes peptide bonds whether in proteins or peptides. [serine proteases] [of HIV] [inhibitors]
Proteasomes
Proteinase
Enzyme that hydrolyzes the peptide bonds of proteins.
Protein C
Protein chips
Protein Kinases
[PKA (cAMP-dependent)] [and memory] [PKC (calcium-dependent)] [PKG (cGMP-dependent)]
Proteins
[general discussion] [protein synthesis] [protein kinesis] [protein domains]
Proteobacteria
Proteoglycans
Proteome
Prothallus
Prothoracicotropic hormone (PTTH)
Protists
Proton
Positively charged particle found in the nuclei of all atoms. The hydrogen ion (H+) is a proton. [More]
Protonema
Proto-oncogene
A normal cellular gene that, when mutated or inappropriately expressed, can cause a cell to become cancerous. Designated c-onc. They normally participate in the control of the cell cycle. [More]
Protoplast
A cell (plant or bacterial) from which the cell wall has been removed.
Protostomia
Protozoa
Proximal
Situated near the place of origin or attachment.
Prozac
Pseudoautosomal region
Pseudocyclic photophosphorylation
Pseudogene
Nonfunctional gene present in the genome of a population. Pseudogenes arise from two different mechanisms: Pseudogenes are designated with the Greek letter psi, e.g., ΨHBBP1 is a nonfunctional version of the gene encoding the beta chain of human hemoglobin. The human genome contains some 19,000 pseudogenes.
Psychedelic drugs
PTTH
Pulmonary system
[human lungs] [their blood supply] [lungs of other vertebrates]
Pupa
Pupil
of human eye
Purines
[analogs used as immunosuppressants]
Pyramids of energy, biomass, and numbers
Pyrethroids
Pyrimidines
Pyrosequencing
PYY3-36

Q

q arm of chromosome
Quantitative Trait Loci (QTL)
Quaternary structure
Refers to complexes of two or more polypeptide chains held together by noncovalent forces but in precise ratios and with a precise 3-D configuration. [More]
Queen Victoria
Quinolone antibiotics

R

Races (subspecies)
Radiation
[ionizing] [and cancer] [spectrum of electromagnetic radiation]
Radicle
Root portion of the embryo of seed plants. [View]
Radioimmunoassay (RIA)
Radioimmunotherapy
RAF gene
RAG-1 and RAG-2
Recombination Activating Genes
Random assortment of chromosomes in meiosis
Rapamycin
[as immunosuppressant] [as regulator of transgene expression]
RAS gene
Rate of natural increase (r)
RB (retinoblastoma gene)
Reactant
Substance that enters into a chemical reaction.
Reactive oxygen species (ROS)
Recapitulation
Occurrence, in embryonic development, of stages thought to have occurred in the embryonic development of its ancestors. [Discussion]
Receptor editing
Receptor Tyrosine Kinases (RTKs)
Recognition helix
Recombinant DNA
Recombination
[in meiosis] [ in rII locus ] [in T-even bacteriophages] [nodule] [signal sequence (RSS)]
Recommended dietary allowances (RDAs) (table)
Reconsolidation, of memories
Red blood cells
Redox potential
Redox reaction
A chemical reaction in which electrons are transferred from one atom (which is thereby oxidized) to another (which is thereby reduced).
Red Queen hypothesis
Reduction
Process of adding electrons to a substance.
Reductionism
Reflex
[stretch reflex] [withdrawal reflex]
Refractory period
Brief interval following the propagation of an action potential in a neuron or muscle fiber during which it is incapable of propagating a second action potential. [in neurons] [in muscle fibers]
Regeneration
Regulator gene
A gene that encodes a transcription factor and thus controls the expression of other genes.
Relaxin
Releaser
REM (roentgen equivalent man)
Renin
Repetitive DNA
Replication origin
Replicative senescence
Reporter genes
Repressor
[lac repressor] [tryptophan repressor]
Reproduction
[sexual] [asexual]
Reptiles
Resistin
Respiratory burst
Respiratory Syncytial Virus (RSV)
Respiratory system
[human lungs] [their blood supply] [lungs of other vertebrates]
Response element (RE)
A particular DNA sequence which, when bound by a protein specific for it, turns its associated gene(s) on (or off). Many response elements bind to a complex of a hormone with its protein receptor. [steroid response elements] [response element of a protein hormone]
Resting potential
Restriction endonuclease
An enzyme that cuts DNA molecules at, or close to, a certain sequence of nucleotides. [Discussion]
Restriction fragment length polymorphism (RFLP)]
Reticular formation
Retina, human
Retinal
Retinoblastoma
Retinoids
Retinol (vitamin A)
Retrotransposons
Retrovirus
A virus whose genome consists of RNA which, after infection, is copied by reverse transcriptase into DNA. The human immunodeficiency viruses (HIV) are retroviruses. [life cycle] [as vector in gene therapy]
Reverse transcriptase
An enzyme that catalyzes the synthesis of DNA that is complementary to an RNA template; that is, an RNA-dependent DNA polymerase. [More] [inhibitors]
Rh antigens
Rh disease (hemolytic disease of the newborn)
Rheumatoid arthritis
Rhizobia
Rhizoid
Hairlike structure that serves as a root for bryophytes, fern prothallia, and certain fungi and lichens.
Rhizome
Underground stem. [View]
Rhodopsin
Riboflavin (vitamin B12)
Ribonuclease P (RNase P)
Ribonucleic acid (see RNA)
Ribonucleoprotein
A complex of RNA and protein.
Ribose
Ribosome
[structure] [in protein synthesis] [rRNA genes]
Riboswitches
[and gene transcription] [and mRNA translation]
Ribozyme
[general discussion] [synthetic]
Ribulose bisphosphate carboxylase oxygenase (RUBISCO)
[in photosynthesis] [genes] [and photorespiration]
Rickets
Rickettsias
Rifampin
Risk, relative
Ritalin
Rituximab
RNA
Ribonucleic acid. A polymer of ribonucleotides.
[messenger RNA (mRNA)] [ribosomal RNA (rRNA)] [transfer RNA (tRNA)] [small nuclear (snRNA)] [small nucleolar RNA (snoRNA)] [guide RNA (gRNA)] [antisense RNA] [small interfering RNA (siRNA)] [microRNAs (miRNAs)] [tmRNA] [long noncoding RNA (lncRNA)] [rRNA genes]
RNA editing
RNA interference (RNAi)
RNA polymerase
[types in eukaryotes]
RNA thermosensors
RNA World
Robertsonian fusions
Rods of human retina
Root pressure
Roots
ROS (reactive oxygen species)
Rotifers, bdelloid
Rough endoplasmic reticulum (RER)
Rous sarcoma virus (RSV)
r-strategists
RUBISCO
see Ribulose bisphosphate carboxylase oxygenase
RU-486
A progesterone antagonist used to prevent or terminate pregnancy. Also called mifepristone. [More] [still more]

S

Saccharomyces cerevisiae (budding yeast)
[diploid number] [genome] [aging in]
Salmonella
also [Ames Test] [uptake by cells]
Sanger, F.
Saprophyte
Heterotrophic plant (or fungus) that secures its food by the extracellular digestion of nonliving organic matter.
Sarcoma
A cancer produced by a malignant cell of supporting tissue such as muscle, bone, or cartilage. Compare with carcinoma.
Sarcomere
Sarcopterygians
Scaphopoda
Scatchard equation
Schistosomiasis
[life cycle of parasite] [how it evades the immune system]
Schwann cell
SCID (Severe combined immunodeficiency)
[X-linked SCID] [adenosine deaminase deficiency] [defective V(D)J recombination] [in mice]
Scientific papers
[a case study]
Scientific methods
Scion
Detached part of a plant (e.g., a piece of stem) that is grafted onto another plant. [View]
Sclerenchyma
SCR (S-locus Cysteine-Rich protein)
Scrapie
Screwworm fly
Scrub forest biome
Scurvy
[and collagen]
Secondary immune response
Secondary structure, of proteins
Second messengers
Second-set graft rejection
Secretin
Securins
Sedatives
Seeds
Selection
[natural] [kin] [stabilizing, directional, disruptive] [sexual] [ coefficient (s) ]
Selector gene
Gene that regulates the expression of many other genes. Selector genes encode transcription factors. [Examples]
Selenocysteine
Self-incompatibility in plants
Semen
Semicircular canals
Sense strand
The strand of DNA whose 5' -> 3' sequence is the same (substituting T for U) as that of the corresponding mRNA molecule. (Synthesis of this mRNA uses the antisense strand as a template.) [View] The sense strand is sometimes called the Crick strand.
Sensitive
Able to detect a low level of something. The more sensitive the test, the less likely that it will cause "false negatives"; that is, a failure to detect something that is actually present. Compare specific.
Sensitization
Separins
Sepsis
Sequence
The linear order of amino acids in a polypeptide or nucleotides in a nucleic acid.
Serine
Serine proteases
Serotonin
also known as 5-hydroxytryptamine (5HT) [receptors] [serotonin reuptake inhibitors (SRIs)]
Serpins
Serum
Serum sickness
Severe combined immunodeficiency (SCID)
[SCID-X1] [adenosine deaminase deficiency] [defective V(D)J recombination] [in mice]
Sevin
Sewage Treatment
Sex chromosomes
Sex determination
[in honeybees] [environmental]
Sex hormones
Sex organs
[of human female] [of human male]
Sexual reproduction
The production of new individuals following the mixing in a single cell of the genes of two different cells, usually gametes and usually from different parents. [in humans] [in angiosperms] [in gymnosperms] [in mosses] [in ferns] [in bacteria] [in Paramecium]
Sexual selection
Sey ("small eyes") gene
Smallpox
Shade avoidance effect
Shock
Sickle-cell disease
Sievert (Sv)
Signal sequence
A short length of amino acid residues found at the amino terminal of those newly synthesized polypeptides destined to enter the endoplasmic reticulum and, often, removed as they do so. [More] [signal recognition particle (SRP)]
Silencers
Silver Springs ecosystem
SINES (Short Interspersed Elements)
Single nucleotide polymorphisms (SNPs)
Sino-atrial (S-A) node
Sips equation
Sir2 gene
SIV (Simian Immunodeficiency Virus)
Skeleton, human
Skin
hormones of
Skin testing
for immediate hypersensitivities
SLG (S-Locus Glycoprotein)
Slime molds
[cellular] [plasmodial (Myxomycetes)]
SMADs
small eyes (Sey; also Pax6)
mouse gene homologous to eyeless in Drosophila and Aniridia in humans. [More]
Smell, the sense of
Smog, photochemical
Smooth muscle
SNAREs
Snow, John
Sodium/potassium ATPase.
sog ("short gastrulation") gene
Soil
Solute
Dissolved substance in a solution.
Solution
Mixture consisting of molecules or ions less than 1 nm in diameter suspended in a liquid medium (water in most biological systems). [schematic of water dissolving crystal of NaCl]
Solvent
Dissolving medium of a solution.
Soma (somatic cells)
Somatic-cell nuclear transfer (SCNT)
Somatic hypermutation (SHM)
Somatostatin
Somite
One of the blocks of mesoderm that develop in a longitudinal series on either side of the notochord in vertebrate embryos.
Sorus
Southern blot
Speciation
Species
Taxonomic category consisting of a group of actually or potentially interbreeding natural populations that ordinarily do not interbreed with other such groups even when there is opportunity to do so. (The singular and plural are spelled alike.) [More]
Specific
Capable of discriminating between two things. A test that discriminates between infection by the human immunodeficiency virus 1 (HIV-1) and HIV-2 is more specific than one that distinguishes only between infection by any HIV and by the simian immunodeficiency virus (SIV). The more specific a test, the fewer the "false positives"; in this example, the less likely that a patient will be diagnosed as HIV-1 positive when he or she is really HIV-2 positive. Some highly-specific tests and reagents are low in sensitivity and vice versa. Compare sensitive.
Specificity, antibody
Spemann, Hans
[egg-tying experiments] [the organizer] [and eye induction]
Spermatogenesis
S phase of cell cycle
Sphenopsids
Spinal cord, human
Spindle checkpoint
Spiracles, insect
Spirochetes
Spliceosomes
[in pre-mRNA processing] [contain a ribozyme]
Sponges (Porifera)
Sporangium
Structure within which asexual spores are produced. [in ferns] [in mosses] [in slime molds]
Spore
Structure, usually unicellular, which serves to disperse the species and/or enable it to survive unfavorable conditions and which can develop into a new individual.
Sporophyte
Diploid, spore-producing stage in the life cycle of a plant. [in angiosperms] [in ferns] [in mosses]
Sporozoans
Squid, hearts of
SRC gene
SRK (S-Receptor Kinase)
SRY
Gene on the Y chromosome that determines maleness. [More]
Stahl, F. W.
Stamen
Standard
[deviation] [error of the mean (S.E.M.)]
Staphylococci
Starch
Stele
Stem cell
A cell that gives rise to both differentiated descendants as well as more stem cells. [general discussion with links to other pages]
Stems, plant
Stereocilia
Sterile-male technique
Steroid
One of many fat-soluble, biologically active compounds whose molecules contain a system of 4 rings made up of 17 carbon atoms.
[cholesterol] [receptors and response elements] [sex hormones] [progesterone] [adrenal hormones]
Sticklebacks
[evidence of sympatric speciation] [mating behavior] [Pitx1 gene]
Stigma
Stimulus
Anything that initiates a response in a cell or organism.
Stolon
Stomach
[physiology]
Stomata
[Discussion] [hormonal control]
STR (Short Tandem Repeat)
Streptococci
Streptococcus pneumoniae
[rough and smooth] [types] [genome]
Striatum
Strigolactones
Stroma, of chloroplast
Suberin
Subspecies (races)
Substance P
Substantia nigra
Substrate
(1) Substance that is acted upon by an enzyme. (2) Base (e.g., soil, rock) upon which an organism lives. Also called the substratum.
Subtilisin
Succession, plant
Sucrose
Sugars
Sulfhydryl group
Sulfur dioxide (SO2) and acid rain
Superoxide anion
Superoxide dismutase (SOD)
Suprachiasmatic nuclei (SCN)
Sup35p
Survivorship curves
Suspension
Mixture containing solid particles larger than 100 micrometers distributed throughout a liquid. The particles will eventually settle out under the force of gravity.
Symbiosis
Sympathetic nervous system, in humans
Sympatric speciation
Symplast
Symport pumps.
Synapses
[in nervous system] [electrical] [immunological]
Synapsida
Synapsis
Union, side-by-side, of homologous chromosomes early in meiosis I.
Synaptonemal complex (SC)
Syncytium
Mass of cytoplasm containing many nuclei. It can be formed by the fusion of cells (e.g., skeletal muscle fibers) or by the repeated mitosis of nuclei without accompanying cytokinesis (e.g., insect blastula).
Syndecan-1
Syndrome
A collection of symptoms and signs characteristic of a particular disease.
Syntenic
Refers to genes present on the same chromosome. [Examples]
Syphilis
System
Group of organs that perform one or more functions as a unit (e.g., the organs of the digestive system).
Systemic lupus erythematosus (SLE)
Systole

T

T2 virus
[gene mapping] [Hershey-Chase experiment]
T4 virus
[rII locus]
TACO (tryptophan-aspartate coat protein)
Taenia solium
Taiga
TALENs (Transcription Activator-Like Effector Nucleases)
Tanning
TAP = Transporter associated with antigen processing
Tapeworms
Taste, in humans
TATA box
Tatum, E. L.
Taxes
Taxol
Taxonomy
Classification of organisms. [Discussion]
Tay-Sachs disease
TBP (TATA-binding protein)
TCDD (dioxin)
T cell
Lymphocyte that matures within the thymus. [Discussion] [CD4+ subset] [CD8+ subset] [Helper subsets (Th1, Th2, Tfh, Th17)] [Cytotoxic T Lymphocytes (CTL)] [Regulatory T cells] [Gamma/Delta T cells]
TCR
T-cell receptor for antigen. [More] [gene segments]
Telomerase
[and replicative senescence]
Telomeres
Temperate
[deciduous forest] [rain forest]
Tendon
Teratocarcinoma
Teratogen
A substance that causes birth defects.
Teratoma
Tertiary structure, of protein
Tesla
Test cross
[monohybrid] [dihybrid]
Testes, human
Testosterone
Tetanus
Sustained maximal contraction of a muscle. [More]
Tetracycline antibiotics
Tetracycline response element
Tetrad
(1) The duplicated homologous chromosomes held together by chiasmata prior to anaphase of meiosis I. [View] Each tetrad contains four chromatids. (2) The four products of meiosis kept together like the four spores in the ascus of budding yeast. [View]
Tetrahymena thermophila
Tetraparental mouse
Tetrapods
TFIID (Transcription factor IID)
Thalamus
Thalassemia
THC (delta-9-tetrahydrocannabinol)
Thecodonts
Thelytoky, automictic
Therapsids
Thermoacidophiles
Thiamine (vitamin B1)
Thick (and thin) filaments of muscle
Thoracic duct
Three-point cross
[in corn (maize)] [in T2 bacteriophage]
Threonine
Threshold
[of response to toxic agents] [of neurons] [of skeletal muscle]
Thrombin
Thrombocytopenic purpura, immune
Thrombomodulin
Thrombopoietin
Thromboxanes (TXs)
Thylakoid
[structure] [and light reactions]
Thymidine kinase
Thymine
Thymus
[function]
Thyroid gland
Thyroid-stimulating hormone (TSH)
Thyrotoxicosis (Graves' disease)
Thyrotropin-releasing hormone (TRH)
Tight Junctions
Timeless (tim) gene
Tinbergen, N.
Tissue
Association of cells bound together by cell walls (plants) or extracellular matrix (animals) that performs particular functions. [plant tissues] [animal tissues]
Tissue Factor (TF)
Tissue plasminogen activator (TPA)
Tissue typing
Titer
Titin
Tocopherol (vitamin E)
Tolerance, immunological
Toll-Like Receptors (TLRs)
Tonus
Sustained, partial contraction of a muscle. [More]
TOR ("target of rapamycin")
Torr
A unit of pressure equal to that exerted by a column of mercury 1 mm high; hence equal to the unit mm Hg.
Total fertility rate (TFR)
Touch, sense of
Toxic shock syndrome
Toxin
Metabolic product (usually a protein) of an organism that is poisonous to another organism.
Toxoid
Toxin treated to destroy its poisonous quality but leaves it capable of stimulating the production of antibodies that will be able to bind to the unaltered toxin. The DTP vaccine contains both diphtheria and tetanus toxoid.
Toxoplasma gondii
Tracheal system of insects
Tracheophyte
A plant with a vascular system of xylem and phloem. Includes all plants except mosses and their relatives.
Tranquilizers
Transcription
The synthesis of a sequence of ribonucleotides complementary to the sequence of deoxyribonucleotides in a molecule of DNA. [Discussion]
Transcription factor
A protein needed to initiate the transcription of a gene. Some transcription factors bind to specific sequences of DNA (promoters and enhancers); others bind to each other; many bind both to DNA as well as to other transcription factors.
[general discussion] [selector genes] [glucocorticoid receptor] [jun,fos,myc] [E2F] [TFIIH] [isolating transcription factors by affinity chromatography]
Transcriptome
Transducin
Transduction
Trans fatty acids
Transformation
1. The modification of the genotype of a cell by introduction of DNA from another source. [Discussion]
2. The conversion of a normal cell into a cancerous one. [Discussion]
Transforming Growth Factor-β
Transgenic
An animal or plant that has been deliberately transformed with a foreign gene and is able to pass that gene on to future generations in its gametes. [making transgenic animals] [making transgenic plants]
Transitions (in DNA)
Translation
The synthesis of a polypeptide in accordance with the genetic information encoded in a molecule of messenger RNA (mRNA).[Discussion]
Translocation
(1) Transfer of a piece of one chromosome to another, nonhomologous, chromosome. [More] [Example: Philadelphia chromosome]
(2) Transport of proteins in (and out) of the endoplasmic reticulum.
(3) Transport of materials, e.g., water and food, from one part of a plant to another.
Transmembrane protein
Protein that passes one or more times through the lipid bilayer of a cell membrane. [color schematic (48K)]
Transmissible spongiform encephalopathies
Transpiration
Transpiration-Pull
Transplantation
[ discussion of organ and tissue transplantation ] [ transplants of hematopoietic stem cells ]
Transport vesicle
Membrane-enclosed structure that shuttles soluble as well as integral membrane proteins to various destinations within the cell. [More]
Transposons
Transversions (in DNA)
Trematoda
Tricyclic antidepressants
Triglyceride
Trihalomethanes (THMs) (by-products of water chlorination)
Trilinolein
Trinucleotide repeats
Trisomy 21
Tristearin
Trochophore larva
Trophic level
Trophoblast
Tropical rain forest biome
Tropisms
Troponin and Tropomyosin
TRPV receptors
Trypanosomiasis (African sleeping sickness)
[how the parasite evades the immune response]
Trypsin
Tryptophan
[structure] [repressor]
TSH
Thyroid-stimulating hormone
T system
Tubular secretion
Tubulin
Tularemia
Tumor-infiltrating lymphocytes (TIL)
Tumor necrosis factors (TNF)
[and inflammation] [and apoptosis] [TNF-β (lymphotoxin)] [TNF-α receptors]
Tumor Suppressor Genes
Tundra biome
Tunicata (Urochordata)
Turbellaria
Turgor
[in guard cells of leaf]
Turner syndrome
Two-hybrid system
Tyrosine
Tyrosine kinases

U

Ubiquitin
UCP1 (Uncoupling Protein 1)
Ultrabithorax (Ubx)
Ultraviolet
[radiation] [and ozone shield] [vision]
Units, scientific]
Uracil
Ure2p
Urea cycle
Uric acid
Urine, formation of
Urochordata (Tunicata)
Urticaria (hives)
Utriculus

V

V2 receptors
Vaccine
Preparation of dead or weakened pathogens, or their products, which when introduced into the body, stimulates the production of protective T cells and/or antibodies without causing the disease. [Discussion] [flu vaccines] [against AIDS] [against smallpox]
Vacuoles, in plant cells
Vagus nerves
[effect on the heart]
Valence
Number of electrons gained, lost, or shared by an atom in bonding to one or more other atoms. [Discussion] [types of chemical bonds between atoms]
Valine
Variable number of tandem repeats (VNTRs)
Variant surface glycoprotein (VSG) of trypanosomes
Variation, continuous
Variola virus
Variolation
Vascular
Containing vessels that conduct liquid.
Vasectomy
Vasopressin (arginine vasopressin, the antidiuretic hormone)
V(D)J Joining
Vector
(1) An animal (e.g., an insect) that transmits a parasite. [Example] Reducing the population of a vector is often a good way to lower the incidence of the disease it transmits. (2) In genetic engineering, a virus or plasmid that carries a molecule of recombinant DNA into a cell, thus transforming it. [retroviral vectors] [adeno-associated virus (AAV) as a vector]
VegT
Venter, J. C.
[minimal genome] [synthetic genome]
Ventral tegmental area (VTA)
Vernalization
Vertebrate
Any backboned animal. Includes fishes, amphibians, reptiles, birds, and mammals. [Discussion] [comparative kidney structure and function] [vertebrate lungs] [vertebrate hearts] [vertebrate brains]
Vestigial
Term applied to a degenerate or incompletely developed structure which was more fully developed at an earlier stage of the organism and/or its ancestors.
Vibrio cholerae
Viking missions to Mars
Villi
Vimentins
Virion
Viroids
Viruses
[general discussion] [latent] [RNA viruses]
Virusoids
Viscera
Organs in the body cavity.
Vision
[in humans] [processing visual information] [in insects] [ultraviolet]
Vitamins
[in human nutrition] [Recommended Dietary Allowances (RDAs)]
Vitamin K
Vitreous body
Viviparous
Having embryos that develop to adult form within the mother's body while securing most of their nourishment from the mother's tissues rather than from the yolk of the egg.
Volvox
Vomeronasal organ (VNO)
von Frisch, K.
von Willebrand Factor (vWF)

W

Waldenström's macroglobulinemia
Water
[properties] [transport in plants]
Water molds (Oomycetes)
Watson, J. D.
Weismann
Continuity of Germplasm
Went, F. W.
Werner's syndrome
Western blot
Wiesel, T. N.
Wilms' tumor
wingless (wg) gene
Wnt signaling
Wolbachia

X

X chromosome
[X-chromosome inactivation (XCI)] [role of XIST locus]
Xenarthra
Xenopus laevis, the South African clawed frog.
Xenotransplantation
Graft of an organ or tissue between members of different species. [More]
Xeroderma pigmentosum (XP)
XIST
X-linkage
X-linked adrenoleukodystrophy (X-ALD)
X-linked agammaglobulinemia
X-linked SCID
Xylem
[ transport in ] [in roots]

Y

Y chromosome
Yeast
A unicellular fungus. One species, the budding yeast Saccharomyces cerevisiae, is used in brewing and baking because of the ease with which it ferments carbohydrates to ethyl alcohol and carbon dioxide.
Yeast two-hybrid system
Yellowthroat, subspecies of
Yersinia pestis
Yolk sac

Z

Zeatin
Zebrafish (Danio rerio)
Zellweger syndrome
Zero population growth (ZPG)
Zidovudine (AZT)
Zinc
nutritional requirement
Zinc finger
[glucocorticoid receptor] [steroid hormone receptor superfamily] [zinc-finger nuclease]
Zoology
Study of animals.
Zoospore
Flagellated, swimming spore produced asexually.
Z-scheme (in photosynthesis)
Zygomycetes
Zygote
Cell formed by the union of two gametes.
Zygotene
Zymogen