A. The agouti locus in mice has three alleles: a is recessive and confers a blac

Question

A. The agouti locus in mice has three alleles: a is recessive and confers a black coat, A is dominant to a and confers an agouti coat, and AY is dominant to both and confers a yellow coat. AY is also a recessive lethal. In addition, the independently assorting c allele is recessive (to C) and prevents the mice from making any fur pigments at all, resulting in albinos. Two mice are crossed, and produce offspring in a ratio of 3 albino : 2 yellow : 1 black. What are the genotypes and phenotypes of the parent mice?

B. In Drosophila, the X-linked recessive mutation vermillion (v) causes bright red eyes, in contrast to the brick-red eyes caused by the wild-type allele. A separate autosomal recessive mutation, suppressor of vermillion (su-v), causes flies homozygous or hemizygous for v to have wild-type eye color. In the absence of vermillion alleles, su-v has no effect on eye color. Determine the F1 and F2 phenotypic ratios from a cross between a vermillion female with wild-type alleles at the su-v locus and a male with a wild-type allele at vermillion, but who is homozygous mutant at su-v.  

Explanation / Answer

Alleles ; a recessive - black coat , A is dominant - yellow coat , C - independent allele ,albino allele ,

consider ; ay -recessive , AY - dominant , CC - independent allele .

so , the genotype of the parents ;

parent 1 ; AaYC , parent 2 ; AyCa

phenotypes ; yellow ,parent 1, albino - parent 2

answer for B;

X- linked recessive allele , male parent has - only one gene in XY , female parent XX ,2 alleles . males are generally heterozygous , females are homozygous , carrier females have only one unaffected gene where it will not express the gene .

so homozygous gene is female .

f1 and f2 ratios;

F1 ; 1/2 will be normal female X+ Xv S -V+ / s-v  , 1/2 will be normal male

F 2 ; 8 /16 are wild type females ,5/16 are wild type males ,3/16 are vermillion males

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