Locus 1 controls fur color in mice. Allele B for black and allele b for brown ar

Question

Locus 1 controls fur color in mice. Allele B for black and allele b for brown are codominant. Locus 2 controls the expression of alleles at locus 1. Allele Q allows expression and allele q prevents expression so that genotypes qq have white fur. The loci are on nonhomologous autosomes and so, they segregate independently of each other and alleles and all genotypic classes exhibit 100 % penetrance and full expressivity. Genotypes BbQq and BbQq mate and produce 300 progeny.

1. What is the expected ratio among the phenotypic classes (provide the class and the respective proportion of the total progeny).

2. What is the expected number of genotypic classes expected among the progeny.

3. What is the number (not a fraction) of progeny expected to be true-breeding for fur color. SHOW YOUR WORK

Explanation / Answer

Based on the given data,

The genotype in locus I, are:

The presence of Q allele in locus II allow the expression of alleles in Locus-I, whereas q prevents the expression. Thus,

These loci are present on nonhomologous autosomes and have 100 % expressivity and penetrance. The cross between the BbQq × BbQq results, total progeny 300, therefore:

1)

The expected ratio among the phenotypic classes is:

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