Males of silkworm Bombyx more are known to produce more silk per unit quantity of leaf consumed. Hence, they are preferably bred in sericulture industry. Which of the following genotypes should be crossed in order to get maximum fraction of male insects ?

Note : `SL_(1)` and `SL_(2)` are sex-linked recessive lethal mutations

Options

A. (i) and (iv)
B. (i) and (iii)
C. (ii) and (iii)
D. (ii) and (iv)

Answer

B

Explanation

In silkworm, ZZ individuals are males while ZW individuals are females `SL_(1)` and `SL_(2)` are sex-linked recessive lethal mutations which, if present in homozygous condition, can be lethal and may lead to death of the individual. In order to get maximum fraction of male insects (i) and (ii) should be crossed because there will be 50 % of the male progeny that will be completely normal and free of lethal allele.