A recessive allele (d) of the dancer gene in mice affects the inner ear and results in mice with balance problems and an unusual gait. You learned in class that the A gene, which is on a different chromosome, has an allele, AY, that is dominant for yellow coat color and recessive lethal.
You cross a pure-breeding line of dancer mice that have normal coats to a strain with normal gait and yellow coats. In the resulting F1 progeny, 1/2 have yellow coats and normal gaits and 1/2 have normal coats and normal gaits.
What are the possible genotypes of the yellow-coated F1 progeny?
Select one or more:

a. DDAA
b. DdAA
c. DdA^YA^Y
d. DdAA^Y
e. ddA^YA^Y
f. DD AA^Y
g. ddAA

d. DdAA^Y

Explanation:

Given,

Normal gait (D) is dominant over dancer gait (d)

AY = yellow coat color

AYAY = lethal

Parent 1 : pure breeding dancer mice with normal coat = ddAA

Parent 2 : normal gait with yellow coat

In the F1 generation, the entire progeny has normal gait, so it can have DD or Dd genotype. Since it always gets one recessive d allele from parent 1, it must get one dominant D allele from parent 2. Hence, entire F1 progeny will have Dd genotype and they will have normal gait.

Half of the progeny is yellow and half is normal colored. Since it gets one  allele A from parent 1,  parent 2 must have AAY genotype to produce half AA (normal colored) and half AAY (yellow colored) offspring.

So, possible genotype of yellow-coated progeny in F1 is DdAAY.

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