Genetics Problems
(multi-trait crosses)

Pictured above is an alien who displays all of the dominant characteristics of its species.  Below is a chart listing various traits found in this alien race.  Use the information in the chart to solve the genetics problems that follow.

Trait Dominant Phenotype Recessive Phenotype
Body color  (B)  purple  (b)  red 
# of Eyes (E)  (e) 
Vision (V)  20/20 - no glasses required  (v)  glasses needed 
Size of Lips (L)  thin  (l)  thick
Hair (H)  absent (h)  present
Diet / Type of Teeth (D)  pointed = carnivore  (d)  blunt = herbivore 
Location of Nostrils  (N)  front of head, above mouth  (n)  top of head, between eye stalks
# of Tentacles (T)  8 (t)  4
Tentacle Suckers (S)  present (s)  absent

 

1.  A carnivorous male with 4 tentacles mates with an 8-tentacled female who also eats meat.  The male is heterozygous for the diet trait.  The female's tentacle genotype is hybrid but her diet genotype is pure.  What is the chance this couple will produce a carnivorous baby with 8 tentacles?  answer

2.  A red male with thin lips mates with a thin-lipped purple female.  The female is heterozygous for the body color trait.  As for the lips, both aliens are heterozygotes.  What is the chance that their baby will be red and have thick lips?  answer

3.  A blunt toothed male with hair and glasses mates with a hairless female who wears glasses and has pointed teeth.  The male's entire genome is pure.  The female does not have hair but does carry the hair allele.  She is homozygous for the tooth shape.  What is the chance of this couple having a hairless baby with pointed teeth that needs glasses?   answer

4.  A purple male with 1 eye and nostrils on the top of his head mates with a 2-eyed, red female whose nostrils are above her mouth.  Both aliens have been tested and have hybrid genotypes for any dominant phenotype they display.  What is the chance of their baby's genome being pure for all three traits?  answer

5.  Rock, a thin-lipped male that lacks tentacle suckers, is having a baby with Amber, a thick-lipped female who also lacks tentacle suckers.  Rock fell in love with Amber because of her thick lips.  Rock's mother had thick lips and it is common for this alien species to select a mate with features similar to the maternal parent.  What is the chance that Amber will give birth to a thin-lipped baby that has tentacle suckers?  answer

6.  Two hairless, purple aliens with 8 tentacles and 20/20 vision mate.  Both aliens are heterozygous for the body color trait.  The male is hybrid for the vision trait, the female is pure.  The male's eight tentacles are the result of two dominant alleles while the female is a carrier of the 4 tentacle trait.  The homozygous hairless genotype is found in both the male and the female.  What is the chance that this pairing will produce a baby with the following phenotype: red, hairless body with 8 tentacles and perfect vision?  answer

7.  This one will test your math skills!
If two aliens hybrid for all of the traits listed above mate, what is the chance that the baby will be purple, have 1 eye, 20/20 vision, thick lips, hair, pointed teeth, nostrils on the top of the head and 8 tentacles but no tentacle suckers? answer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answers

 

1.  male = Dd tt     female = DD Tt

     chance of carnivorous baby with 8 tentacles = 8/16 = 1/2 or 50%
          [4/4 chance for carnivorous baby]
          [2/4 chance for 8-tentacled baby]

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2.  male = bb Ll     female = Bb Ll

     chance of red baby with thick lips = 2/16 = 1/8 or 12.5%
          [2/4 chance for red baby]
          [1/4 chance for thick-lipped baby]

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3.  male = dd hh vv                  female = DD Hh vv

     chance of hairless baby with pointed teeth that needs glasses = 32/64 = 1/2 or 50%
          [4/4 chance for baby with pointed teeth]
          [2/4 chance for hairless baby]
          [4/4 chance for baby needing glasses]

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4.  male = Pp ee nn                  female = pp Ee Nn

     chance of baby's genome being pure for all three traits = 12/64 = 3/16 or 18.75%
          [3/4 chance for pure body color genotype]
          [2/4 chance for pure # of eyes genotype]
          [2/4 chance for pure location of nostrils genotype]

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5.  Rob = Ll ss     Amber = ll ss

     chance of thin-lipped baby that has tentacle suckers = 0%
          [2/4 chance for thin-lipped baby]
          [0/4 chance for baby to have tentacle suckers] - this one makes the entire combination impossible

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6.  male = HH Pp TT Vv     female = HH Pp Tt VV

     chance of baby  having a red, hairless body with 8 tentacles and perfect vision = 64/256 = 1/4 or 25%
          [4/4 chance of being hairless]
          [1/4 chance for red body color]
          [4/4 chance for 8 tentacles]
          [4/4 chance for perfect vision]

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7.  male = Bb Ee Vv Ll Hh Dd Nn Tt Ss     female = Bb Ee Vv Ll Hh Dd Nn Tt Ss

     chance baby will be purple, have 1 eye, 20/20 vision, thick lips, hair, pointed teeth, nostrils on the top of the head and 8 tentacles but no tentacle suckers = 81/262144 or 0.03%
          [3/4 chance for purple body]
          [1/4 chance for 1 eye]
          [3/4 chance for 20/20 vision]
          [1/4 chance for thick lips]

          [1/4 chance for hair]
          [3/4 chance for pointed teeth]
          [1/4 chance for nostrils on the top of the head]
          [3/4 chance for 8 tentacles]
          [1/4 chance for no tentacle suckers]

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