An F1 is created by crossing a pure breeding ebony female fly to a pure breeding

Question

An F1 is created by crossing a pure breeding ebony female fly to a pure breeding white male fly. (ebony is an autosomal recessive mutation; you know what white is.). You make a Punnett square to predict the F2 progeny from an incross. With which alleles do you populate the columns of the Punnet square for the male of the cross? (Because of the total lack of style in elearning, I am using e-, e+, w- and w+ as my nomenclature. et/e- w+/w- e+ e- w+ w- e+ Y w+ Y e+ e- X X e+/e- w+/Y e+/e- w-/Y e+ e- w+ Y

Explanation / Answer

According to the information, the female is an ebony type whereas the male is a white-eyed. Thus, the respective genotypes of female and male would be given by e+/e+ and w-/w-. Thus, this cross would give rise to only a single type of combination in the F1, i.e. e+/w-. Selfing of these F1 flies would give rise to following combinations:

Since the trait of ebony eye is autosomal recessive in nature, only the homozygous flies would be affected by this eye-color irrespective of their sexes.

Hence, it can be seen here that the male flies of this F2 population can have e+w+, w-w-, w+w- or e+w- genotypes.

This suggests that choices 1,2,5,6, 13 and 15 are correct.

e+ w- e+ e+e+ e+w- w- e+w- w-w-

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