Question

In: Biology

2. Black bodies and vestigial wings in Drosophila are caused by recessive alleles on chromosome 2....

2. Black bodies and vestigial wings in Drosophila are caused by recessive alleles on chromosome 2. A long-winged male with yellow-brown body color, homozygous for the wild-type alleles, b+b+ v+v+, was exposed to X-rays to induce mutations in germ-line cells (i.e. to generate mutations in the gametes the male produced). He was then mated to a homozygous recessive black-bodied, vestigial-winged female, bb vv. Among the offspring, a male with a black body and vestigial wings was observed.

a. What are the expected genotypes and phenotypes of the progeny of the cross given above?

b. Describe a chromosomal rearrangement that would explain the observed black-bodied, vestigial-winged male.

Expert Solution

These are autosomal recessive traits.

b+b+ v+v+= A long winged male with yellow-brown body color.

bb vv= A vestigial winged female with black body.

Male b+b+ v+v+ was exposed to Xrays which cause mutations in their germ cells. So gametes genyotype was changed.

Cross per formed between mutaed male with bbvv female

b+b+ v+v+ (Mutated)X bbvv gives bbvv offspring.

Normally from b+b+ v+v+, b+v+ gametes is formed.

Similarly from bbvv, bv gamete is formed.

From thie we expect all progenies are b+b v+v genotype, means all are Yellow brown with long wings. But surprisingly bbvv genotye also observed. This is due to mutation of male. This mutant change the germinal cells.

a) b+b v+v X bbvv

?

F1: 1 b+b v+v: 1b+b vv:1 bb v+v: 1 bbvv genotypic ratio

1 Yellow long: 1 Yellow vestigial: 1 black long: 1 black vestigial.

b)

gladiator answered 2 years ago

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