You are encouraged to work in groups on these problems but y

You are encouraged to work in groups on these problems, but you should write your own answers - do not copy directly from classmates or any other source. Please show your work and define your symbols clearly. Duchene muscular dystrophy is an X-linked recessive disorder that causes progressive muscle weakening. Consider a healthy woman whose brother has Duchene muscular dystrophy. What is the probability she will base an affected child? If your mother\'s brother (your uncle) has Duchene muscular dystrophy, what is the probability that you have inherited the disease allele?

Solution

Answer:

(1)

Answer: 1/8

Affected brother: XmY

Woman whose brother is affected: XX or XmX (1/2 or 50% chances that she is a carrier)

If a carrier female marries a normal man there is ¼ chances that she could have a child with Duchenne dystrophy.

The above mentioned woman is ½ being a carrier, therefore probability of having a child with Duchenne dystrophy is ½ x ¼ =

(b)

If a carrier female marries a normal man there is ½ child will inherit the disease allele.

My mother being a disease carrier = ½

Me carrying the disease allele= ½ x ½ =1/4

In an X linked recessive inheritance, two copies of a disease allele on the X chromosome are required for an individual with two X chromosomes (a female) to be affected with an X-linked recessive disease.

For a carrier female, with each pregnancy there is a one in two (50%) chance her sons will inherit the disease allele and a one in two (50%) chance her daughters will be carriers.