For a child with Duchenne's muscular dystrophy, what is the chance that daughters will be carriers, and sons will develop the disease?

For a child with Duchenne's muscular dystrophy, what is the chance that daughters will be carriers, and sons will develop the disease?

• A. a. daughters have a 50% chance of being carriers, sons a 50% chance of developing the disease
• B. b. both daughters and sons have a 50% chance of developing the disease
• C. c. each child has a 1 in 4 (25%) chance of developing the disorder
• D. d. sons only have a 1 in 4 (25%) chance of developing the disorder

Answer: (A)

The situation described in the question pertains to genetic inheritance patterns, specifically X-linked recessive disorders such as Duchenne's muscular dystrophy, which typically affects boys more than girls. In this genetic model, the gene for Duchenne's muscular dystrophy is located on the X chromosome. Since the mother has one X chromosome with the mutation (if she is a carrier) and the father has a Y chromosome (since it is a male), the inheritance patterns are as follows: - Every daughter will inherit one X chromosome from their father (which will be Y-contingent and won't pass on the disease) and one X chromosome from their mother. Therefore, they have a 50% chance of inheriting the mutated X chromosome from their carrier mother, making them carriers themselves. - Every son inherits their father's Y chromosome and one of the mother's X chromosomes. If the mother is a carrier, there is also a 50% chance that she will pass on the X chromosome with the mutation. If a son inherits the affected X chromosome, he will express the disease since he has no other X chromosome to compensate. Therefore, the chance of daughters being carriers is indeed 50%, and the chance of sons developing the disease is also 50%.

The situation described in the question pertains to genetic inheritance patterns, specifically X-linked recessive disorders such as Duchenne's muscular dystrophy, which typically affects boys more than girls. In this genetic model, the gene for Duchenne's muscular dystrophy is located on the X chromosome.

Since the mother has one X chromosome with the mutation (if she is a carrier) and the father has a Y chromosome (since it is a male), the inheritance patterns are as follows:

• Every daughter will inherit one X chromosome from their father (which will be Y-contingent and won't pass on the disease) and one X chromosome from their mother. Therefore, they have a 50% chance of inheriting the mutated X chromosome from their carrier mother, making them carriers themselves.

• Every son inherits their father's Y chromosome and one of the mother's X chromosomes. If the mother is a carrier, there is also a 50% chance that she will pass on the X chromosome with the mutation. If a son inherits the affected X chromosome, he will express the disease since he has no other X chromosome to compensate.

Therefore, the chance of daughters being carriers is indeed 50%, and the chance of sons developing the disease is also 50%.