Suppose gene p is s*x-linked, recessive, and lethal. Man marries woman who is heterozygous for this gene...?

Question

If this couple had many normal children, what would be the predicted s*x ratio of these children?

a. 1:2 females:males

b. 2:1 females:males

c. All males

d. All females

Answer 1

The answer is:

b. 2:1 females:males

because half of the males would be lethal and would not be seen as offspring.

Also remember that s*x-linked could also be a Y-linked trait as well as an X-linked one.  In this case gene p has to be an X-linked trait because it's recessive lethal, but just wanted you to understand that.

Answer 2

The man is XY and the woman is XpX

_ _ _ Xp _ _ X

X _ XpX _ XpX

Y _ XpY _ XY

This cross gives 4 offspring, 2 males and 2 females, but one of the males carries the recessive trait and is therefore not born, so there would be 2 females and 1 male

The answer is B, 2:1 females:males