Question

Patterned baldness is a sex influenced trait more expressed in a male. If b+ is normal allele making non-bald phenotype and b is mutant leading to bald phenotype, for a cross between a bald mother and normal father, what is the probability of a bald son?

(a) 0

(b) 1/4

(c) 1/2

(d) 1

This question was posed to me at a job interview.

I'm obligated to ask this question of Sex Influenced Traits and Sex Limited Traits in section Chromosomes and Sex Determination of Cytogenetics

Answer 1

Right option is (d) 1

To explain: Baldness is a sex influenced trait, so the mother is certainly b/b and the father is b+,b+. So, the son will get at least one baldness allele from the mother. Heterozygous male expresses the sex influenced trait; hence the son will definitely be bald.