Question

2. A certain recessive, lethal gene is carried on the X chromosome. (Lethal genes are those that result in death.) A man marries a woman who is hybrid for this gene. What sex ratio would be expected among the living children of this couple?
%Male
%Female​
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Answer 1

Answer:

The correct answer is : male : female = 1:2

Male percent = 33.33%

female percent = 66.66%

Explanation:

In this question, it is given that a lethal gene is carried by X chromosome which is recessive which means will cause death if both copies are recessive for this gene.

The cross between normal man and hybrid or heterozygous women

The gametes: XH and Y from man and XH and Xh from women where Xh is recessive letheal allele.

The cross:

         XH                          Y

XH     XHXH                  XHY

        normal female    Normal male

Xh    XHXh                     XhY

      Carrier female       dead male

This explains that out of three offspring two will be females and one male. Thus the percentage will be:

Male : 1*100/3  = 33.33%

Female : 2*100/3 = 66.66%