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.

State the null hypothesis that would be considered with a Chi-Square test.

Explanation / Answer

Locus 1..........control fur colour.........Bb (black and brown with codominance)

Locus 2......... controls expression of locus 1 by Qq

BbQq x BbQq............heterozygous progeny

9:3:3:1 should be the ratio in F2

X2 = (observed - expected)2 / expected

E = 125

Then X2 = 1.4

df = number of classes - 1 = 3

The p is >0.05, so probability is significant, so we accept the results.

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