Nucleic Acids & Protein Synthesis

 

-DNA vs. RNA

  DNA RNA
Function storage of
 genetic info.
transmission of
 genetic info.
Number of Strands 2 1
5-C Sugar deoxyribose ribose
Nitrogenous Bases A, T, C, and G A, U, C, and G

 

-Base Pairing Rules

-DNA DNA (as seen in replication)
     -G
- C and C - G
     -T
- A and A - T

-DNA RNA (as seen in transcription)
     -G
- C and C - G
     -T
- A and A - U
                           A
- U because RNA contains
                                uracil rather than thymine

 

-The Triplet Code

-one set of 3 consecutive nucleotides (bases) represents an amino acid

3 bases in:

DNA mRNA tRNA
"code" "codon" "anticodon"

     

Codon Table 
(mRNA)
1st position
(5' end)
2nd position (middle) 3rd position
(3' end)
U C A G
U Phe 
Phe 
Leu 
Leu 
Ser 
Ser 
Ser 
Ser 
Tyr 
Tyr 
STOP
STOP
Cys 
Cys 
STOP
Trp 
U
C
A
G
C Leu 
Leu 
Leu 
Leu 
Pro 
Pro 
Pro 
Pro 
His 
His 
Gln 
Gln 
Arg 
Arg 
Arg 
Arg 
U
C
A
G
A Ile 
Ile 
Ile 
Met 
Thr 
Thr 
Thr 
Thr 
Asn 
Asn 
Lys 
Lys 
Ser 
Ser 
Arg 
Arg 
U
C
A
G
G Val 
Val 
Val 
Val 
Ala 
Ala 
Ala 
Ala 
Asp 
Asp 
Glu 
Glu 
Gly 
Gly 
Gly 
Gly 
U
C
A
G

  code is:
          -degenerate 
               -64 codons code for 20 amino acids
          -universal 
               -identical for all species

 

-From Gene to Protein

1.  Transcription (DNA mRNA)
                

          -basic steps
            -DNA strands are separated
            -complementary RNA nucleotides pair with 
             one side of the DNA molecule
            -RNA nucleotides are joined (backbone is "sealed")
            -mRNA molecule exits the nucleus while DNA strands rejoin

 

2.  Translation (mRNA polypeptide)
         

          -basic steps
             -initiation

                -ribosome attaches to mRNA strand at the start codon
             -elongation
(shown above)
                -tRNA's deposit amino acids in the proper order
                -peptide bonds link the amino acids together 
             -termination
                -ribosome reaches a stop codon
                    -ribosome detaches from mRNA
                    -completed protein is released

ribosome movement and codon-anticodon base pairing ensure amino acids are arranged in the proper sequence


 

 

  to great graphics

-DNA
     -Access Excellence Graphics Gallery  
     -Yahoo Picture Gallery  
     -Estrella Mountain Community College  
-Protein Synthesis
     -Oak Ridge National Laboratory
     -BioStudio  (animated)
     -New Century College (animated)

 

to more detailed notes

-Molecular Biology Notebook Online
     -DNA structure
     -RNA structure 
-University of Connecticut
     -DNA history, structure, & replication 
-Michigan State University
     -DNA & RNA structure, DNA replication, RNA & protein synthesis (graphics included)
-Eureka ! Science*
     -Protein Synthesis (animations included)
              
*a bit juvenile but good base explanation
-University of Illinois at Urbana-Champaign
     -Protein Synthesis (graphics included)