Question

Consider the following chromosomes and if they are affected by hemophilia.

X = unaffected X chromosome, x = X chromosome affected by hemophilia, and Y = Y chromosome.

If an Xx female and XY male have children, what fraction of their offspring will have an affected chromosome, and what fraction is likely to be affected by hemophilia?

(1 point)
Responses

12
and 13

1 half and 1 third

14
and 12

1 fourth and 1 half

12
and 14

1 half and 1 fourth

14
and 14

Answer 1

Make a Punnett square. Mom produces X and x (½ each); dad produces X and Y (½ each). The four equally likely children are:

- XX (female, no affected X)
- XY (male, unaffected)
- Xx (female carrier, has an affected X)
- xY (male, affected)

So 2 of 4 = 1/2 of offspring carry an affected X chromosome, and 1 of 4 = 1/4 of offspring will actually be affected by hemophilia.