Question

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

Answer 1

Option D.

Step-by-step 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