Question

In mice, black coat color (B) is dominant over brown (b), and a solid pattern (S) is dominant over white spotted (s). Color and spotting are controlled by genes that assort independently. A homozygous black, spotted mouse is crossed with a homozygous brown, solid mouse. All the F1 mice are black and solid. A testcross is then carried out by mating the F1 mice with brown, spotted mice. (1) Give the genotypes of the parents and the F1 mice. (2) Give the genotypes and phenotypes, along with their expected ratios, of the progeny expected from the testcross.

Answer 1

Answer:

1. genotype of parents: black spotted mouse BBss X brown solid bbSS

F1 generation genotype: BbSs

2. test cross

BbSs x bbss

gametes produced: BS Bs bS bs  X    bs

genotype of test cross: BbSs(black,solid)  ,  Bbss (black, spotted)  , bbSs(brown,solid),   bbss(brwon, spotted)  ratio will be 1:1:1:1

Explanation: when you choose genotype of an trait you chose the dominant word first letter as capital. then homozygous trait mean both allele will be in same form either dominant or heterozygous. in f1 generation since, in parents dominant and recessive traits/alleles are there, the progeny will have both the alleles. hence it will be heterozygous.