Question

True-breeding flies with singed bristles (s) and normal wings (L) were crossed to true-breeding flies with normal bristles (S) and vestigial wings (l). All F1 offspring had normal wings and normal bristles. (Note: assume that neither of these genes is X-linked.) The F1 offspring were then crossed to flies with singed bristles and vestigial wings. For the F2 offspring, what genotypes and phenotypes are possible

Answer 1

The correct answer is -

Possible F2 offspring genotypes and phenotypes:

SsLl: normal bristle, normal wing

Ssll: normal bristle, vestigial wing

ssLl: singed bristle, normal wing

ssll: singed bristle, vestigial wing

Step-by-step explanation:

In this case, the genes 's' and 'L' and genes 'S' and 'l' are linked, they will be passed on to the gamete together.

The cross would be as follows:

F1:

Parents: singed bristles and normal wings x normal bristles and vestigial wings

Genotype: ssLL SSll

Gametes: sL Sl

F1: SsLl ( normal bristles and normal wings )

For F2,

Parents: normal bristles and normal wings x singed bristles and vestigial wings

Genotypes: SsLl ssll

Gametes: SL, Sl, sL, sl

Cross:

SL Sl sL sl

sl SsLl Ssll ssLl ssll

Thus the possible offspring will have -

SsLl: normal bristle, normal wing

Ssll: normal bristle, vestigial wing

ssLl: singed bristle, normal wing

ssll: singed bristle, vestigial wing