A color blind man without hemophilia (both X-linked traits) marries a woman who is a carrier for both traits. What is the probability they will have a son with both color blindness and hemophilia? Hemophilia and color blindness are unlinked genes.

a. 1/1

b. 1/16

c. 1/8

d. 1/4

e. 3/16

Option D.

Explanation:

Both genes are linked to X chromosome. They are recessive diseases and a heterozygous gene, which means that two different forms of a particular gene are inherited, one from each parent.

CB : Color blindness carrier, healthy

H: Hemophilia carrier, healthy

h: Disease

cb: Disease

Mom: X (CB/H) X (cb/h) (carrier)

Dad: X (cb/H) Y (color blind man, and dominant for hemophilia - healthy)

Let's make a table

MOM/DAD | X (CB/H) X (cb/h) |

X (cb/H) Y | X (cb/H) X (CB/H) | Healthy girl for H, carrier for cb

X (cb/H) Y | X (cb/H) X (cb/h) | Healthy girl for H, sick for cb

X (cb/H) Y | Y X (cb/h) | Boy sick for cb and h

X (cb/H) Y | Y X (CB/H) | Boy healthy for CB and H

1 probable case, over 4 possible cases