Question

A phenotypically non-bald woman and a bald man produce four bald sons and a non-bald daughter. What are the most likely genotypes of the mother and father?
a. bb and bbb. bb and BBc. Bb and Bbd. Bb and BB

Answer 1

Answer:

b. bb and BB

Explanation:

For example, pattern of baldness is dominant in man and recessive in female. This is because the gene for baldness (B) in heterozygous state (Bb) expresses itself in male but not in female. It means gene B for baldness behaves as a dominant in male and as a recessive in female. In man due to influence of male sex hormone, a single gene for this trait can cause loss of hair.

But in woman (due to the absence of the male sex hormone) two genes are required to produce baldness.

BB or Bb = Bald in males

bb = not bald in male

BB = Bald in females

Bb or bb = not bald in females

Non-bald womam (bb; XX) x Bald man (BB; XY)

                       XB                                              BY

Xb     XX; Bb (non-bald daughter)          XY; Bb (bald son)