Answer to Question #262901 in Genetics for JONATHAN

Question

a. In mice, the allele for coloured fur (C ) is dominant over white fur (c). The allele V for normal behaviour is dominant over the allele v for abnormal behaviour.

Give the genotypes of the parents in each of the following crosses:

i. Coloured, normal mice mated with white, normal mice produced 29 coloured, [5] normal and 10 coloured, abnormal progeny

ii. Coloured, normal mice mated with coloured, normal mice produced 35 coloured, normal, 13 coloured, abnormal, 11 white, normal and 4 white, abnormal progeny

Answer 1

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).