In Colias butterflies there is a rare allele which codes for

In Colias butterflies there is a rare allele which codes for an unusual stripe on the forewing. The S allele acts as a dominant to produce the stripe but is a recessive lethal allele acting early in larval development. The gene is also located on the Z sex chromosome. (Remember, in butterflies females are the heterogametic sex.)  Which of the following statements are true if a striped male and a normal female were crossed? Choose all that apply.

a half of the female offspring would be striped

b half of the male offspring would be striped

c the male parent must be heterozygous

d only males can be striped

e there would be half as many female offspring as male offspring

Solution

If we consider the genotype

ZX - Stripped male..

XX - Normal female..

By doing the cross.. ZX * XX

The offspring are.

ZX (STRIPPED MALE).

ZX ( STRIPPED MALE)..

XX ( NORMAL FEMALE)..

XX (NORMAL FEMALE)..

The correct option are

(a) only males will be stripped..

(b) half as male and female offspring..

(c) equal no of cell to be produced