Five recessive mutations on the right arm of the X chromosome of Drosophila mela

Question

Five recessive mutations on the right arm of the X chromosome of Drosophila melanogaster cause stringy bristle (sg), lazy eyes (ly), tin body (tn), zillion eye (ze), and miniature wing (m) phenotypes. Two wildtype male flies were exposed to X-rays and then mated separately with (non-irradiated) females showing all five recessive traits (Mating 1 and Mating 2). a) Mating 1 produced normal females and sg ly tn ze m males in equal proportions. One of these phenotypically normal females, when mated to a male sibling, produced F2 progeny that consisted solely of normal and fully mutant phenotypes. Why was this result unexpected, and how do you explain it? (ONE or Two sentences.) b. Mating 2 produced sg ly tn ze m males and ly tn females in equal proportions. Explain the result. (ONE sentence.)

Explanation / Answer

Answer:-

Question A

This is as a result of autosomal recessive since unaffected parents produce affected progeny, and so the trait is recessive. As such, the affected daughter must have inherited recessive alleles from both unaffected parents and thus the trait must be autosomal.

Question B

As this touched on X Chromosomes, the pedigree appears to be similar for both males and females are affected, and it appears to be a dominant trait.A

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