7. One of the X chromosomes in a particular Drosophila female but carried recess

Question

7. One of the X chromosomes in a particular Drosophila female but carried recessive alleles of the genes for yellow body color (y). vermilion eye color (V). and forked bristles (f), as well as the dominant X-linked Bar eye mutation (B). Her other chromosome carried the wild-type alleles of all four genes, but the region includingy+v and f+ (but not B+) was inverted with respect to the normal order of genes. This female was crossed to a wild-type male in the cross diagrammed here. had a normal order of genes y+v+f+B f+v+y+B+

Explanation / Answer

7)a. There are no such progenies because, due to the inversion no single crossover ( homologous recombination ) is possible between yv and vf loci.

b. the B locus is not inverted and homology hence still persists. So crossing over can occur between fb locus.

c. Double cross over resulted in such a progeny. Even though yvf got inverted, the v locus resulted in the same location just in an opposite orientation.

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