Genetics Problems
(1-trait, multi-trait, & testcrosses)

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  (P)  Purple  (p)  Yellow 
Head adornment (G)  Green horns  (g)  Gold antenna 
Tongue color (R)  Red  (r)  Black 
Fur  (F)  Present around neck & waist  (f)  Absent - no fur 
Number of fingers (H)  Four  (h)  Seven 
Shape of feet (W)  Webbed  (w)  Clawed

1.  A heterozygous purple male mates with a yellow female.  What is the chance this couple will produce a yellow baby?  answer

2.  A pure red-tongued female mates with a hybrid red-tongued male.  What is the chance this couple will produce a baby with a heterozygous genotype?  answer

3.  Two web-footed aliens mate.  The male alien's mother had claws but the female aliens parents were both homozygous.  What is the chance the mating couple will produce a baby with claws?  answer

4.  A female alien with 4 fingers is married to a 7-fingered male.  They have ten children.  Eight of the children have four fingers but two have seven fingers.  What is the mother's genotype?  answer

5.  A male alien with fur and gold antenna mates with a female alien who lacks fur but has green horns.  What is the chance that this couple will produce a furless baby with gold antenna?  (Note: the aliens were genetically tested and are heterozygous for all dominant traits)  answer

6.  A male hybrid for the tongue and body color but pure for four fingers mates with a female who is homozygous purple but displays the recessive phenotype for the tongue color and the number of fingers.  What is the chance that this couple will produce a purple baby with a red tongue and seven fingers?  answer

7.  A yellow female alien with claws mates with a purple, webbed-footed male.  The couple's first child is purple like his dad but has claws like his mom.  What is the genotype of the child? answer
     The same couple mates again and this time produces twins.  One of the twins looks just like her dad (purple with webbed feet), the other twin also has webbed feet like his sister and his dad but is yellow like his mom.  Provide the genotypes of the twins and the genotype of the father. answer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answers

 

1.  male = Pp     female = pp

     chance of yellow baby (pp) = 50%

return to the problems

 

 

 

 

 

 

 

 

 

 

2.  male = Rr     female = RR

     chance of baby with heterozygous genotype (Rr) = 50%

return to the problems

 

 

 

 

 

 

 

 

 

 

 

3.  male's mother = ww     female's parents = WW
     male = Ww                  female = WW

     chance of baby with claws (ww) = 0%

return to the problems

 

 

 

 

 

 

 

 

 

 

4.  mother = H?     father = hh     4-fingered kids = Hh   7-fingered kids = hh

     mother's genotype has to be Hh based on the production of the 7-fingered kids

return to the problems

 

 

 

 

 

 

 

 

 

 

 

5.  male = Ff gg     female = ff Gg

     chance of furless baby with gold antenna (ff gg) = 4/16 = 1/4 or 25%

return to the problems

 

 

 

 

 

 

 

 

 

 

6.  male = Pp Rr HH     female = PP rr hh

     chance of purple baby with a red tongue and seven fingers = 0%
         [4/4 chance for purple baby]
            [2/4 chance for red-tongued baby]
            [0/4 chance for seven-fingered baby] - this one makes the entire combination impossible

return to the problems

 

 

 

 

 

 

 

7.  male = P? W?     female = pp ww

     purple child with claws = Pp ww [the kid has to be heterozygous for the body color
                                                                            'cuz of mom's genotype]

     return to the problems

 

 

 

 

 

 

 

 

 

     twins:
         female (purple & webbed feet) = Pp Ww
         male (yellow & webbed feet) = pp Ww

     father's genotype = PpWw 
         dad has to be heterozygous for both traits since his 1st child had claws and the
          male twin was yellow - e.g. the recessive phenotypes were produced

return to the problems