In fruit flies, bar-shaped eyes are dominant to normal-shaped eyes. Male offspring from parents that contained only bar-shaped alleles will have bar eyes. If this male (fly#1) is crossed with a normal-eyed female (fly#2) only the female offspring have bar-shaped eyes. If a normal-eyed (fly#3) is crossed with a bar-eyed female (fly#4), whose parents contained only bar-shaped alleles, all their offspring will have bar-shaped eyes. Explain this results and give the phenotypes of the numbered flies in this problem.

Question

anonymous · Answer

B for dominant bar-shaped eyes
b for recessive normal-shaped eyes

Fly1 BB (because both parents have only bar-shaped alleles meaning they can only pass B to this offsprings)
Fly2 bb (since b is a recessive trait it will only show if she has bb)
The offspring of 1 and 2 has bar-shaped eyes because Fly1 can only pass on B and Fly2 can only pass on b meaning they can only produce offsprings with Bb.

Fly3 bb
Fly4 BB
Same reason as before.

|dw:1352609235410:dw|