In drosophila melanogaster the gene for the recessive mutations brown eyes (bw)

Question

In drosophila melanogaster the gene for the recessive mutations brown eyes (bw) and humpy thorax ... in drosophila melanogaster the gene for the recessive mutations brown eyes (bw) and humpy thorax (ht) are linked and 12 map units apart on chromosome 2. A paracentric inversion on chromosome 2 spanning the entire 12 map unit region that includes the two genes has been identified. Given a female that is heterozygous with cis linkage for the two genes

a)With respect to the two genes, what would be the gametic genotypes that could be produced by a female homozygous for the inverted chromosome and in what proportions would they occur.

b)With respect to the two genes, what would be the gametic genotypes that could be produced if the female carried one normal chromosome 2 and one paracentric inversion form and in what proportion would they occur?

Explanation / Answer

a.

If the female is homozygous for inversion chromosome then no effect will occur in the gametes.

Gametes will be:

HtBw=44%; Htbw=6%; htBw=6%; htbw=44%

b.

Result will be: one acentric chromosome, one dicentric chromosome.

Gametes will be: BwHt= 44%; Bwbw= 6%; bwht=44%.

The acentric chromosome will be Htht=6%; this will be deleted.

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