Question

3.6 In mice, the allele C for colored fur is dominant over the allele c for white fur, and the allele V for normal behavior is dominant over the allele v for waltzing behavior, a form of discoordination. Give the genotypes of the parents in each of the following crosses: (a) Colored, normal mice mated with white, normal mice pro- duced 29 colored, normal and 10 colored, waltzing progeny. (b) Colored, normal mice mated with colored, normal mice produced 38 colored, normal, 15 colored, waltzing, 11 white, normal, and 4 white, waltzing progeny. (c) Colored, normal mice mated with white, waltzing mice produced 8 colored, normal, 7 colored, waltzing, 9 white, normal, and 6 white, waltzing progen

Answer 1

Answer:

a)  Parents Genotype should be (CC,Vv) and (cc,VV).

b) The genotypes of the parents are (Cc,Vv) and (Cc,Vv).

c) The genotypes of the parents are (Cc,Vv) and (cc,vv).

Explanation:

                                     (a)

Mating has occured between a normal colored mice whose genotype is C_,V_  and normal white  mice with genotype cc,V_. The offsprings are as follows :

1) normal mice produced 29 colored

2) 10 colored, waltzing progeny.

Thus all offspring are normal. The genotype of the first parent should therefore be CC. Waltzing trait is produced. The V gene should therefore be heterozygous in both traits.

Hence The parent genotypes should be (CC,Vv) and (cc,CV).

                                     (b)

In this case the approximate ratio in which the descendants are produced is 9:3:3:1. Hence genotypes of the parents are (Cc,Vv) and (Cc,Vv).

                                     (c)  

In this case the approximate ratio in which the offsprings are produced is 1:1:1. The genotypes of the parents are (Cc,Vv) and (cc,vv).