Muscular dystrophy is a sex-linked recessive disorder that causes a progressive weakening and loss of muscle in the body. If a male does not have the disorder and a female is a carrier, is it possible for those parents to conceive a daughter with the disorder?

Question

Responses

Yes, because females are XY. Dad can pass on his Y while mom passes on an affected X chromosome.
Yes, because females are XY. Dad can pass on his Y while mom passes on an affected X chromosome.

Yes, because females are XX. Dad will give his unaffected X chromosome and it does not matter which one mom gives since it is a recessive disorder.
Yes, because females are XX. Dad will give his unaffected X chromosome and it does not matter which one mom gives since it is a recessive disorder.

No, because females are XY. Dad can pass on his Y while mom passes on an affected X chromosome.
No, because females are XY. Dad can pass on his Y while mom passes on an affected X chromosome.

No, because females are XX. Dad will give his unaffected X chromosome, so it does not matter which one mom gives since it is a recessive disorder.

Answer 1

To answer your question, we need to clarify how sex-linked recessive disorders, like muscular dystrophy, are inherited.

Muscular dystrophy is indeed a sex-linked recessive disorder, which means that the gene responsible is located on the X chromosome. Males have one X and one Y chromosome (XY) and females have two X chromosomes (XX).

In this scenario:

• The father does not have the disorder, so he has an unaffected X chromosome (X^+) and a Y chromosome (Y).
• The mother is a carrier, meaning she has one affected X chromosome (X^-) and one unaffected X chromosome (X^+).

The possible combinations of X and Y that the parents can pass on are:

1. From the father (XY):

   • X^+ (unaffected)
   • Y

2. From the mother (XX):

   • X^+ (unaffected)
   • X^- (affected)

Now, let's analyze the possible outcomes for their children:

• If they conceive a daughter:
  • The daughter would inherit the X chromosome from the father (X^+) and one of the mother's X chromosomes (either X^+ or X^-).
  • The possible genotypes for the daughter would be:
    1. X^+ (from dad) + X^+ (from mom) = X^+X^+ (unaffected)
    2. X^+ (from dad) + X^- (from mom) = X^+X^- (carrier, but not affected)

In both cases, none of the combinations result in the daughter being affected by the disorder.

Therefore, the correct response to the question is:

No, because females are XX. Dad will give his unaffected X chromosome, so it does not matter which one mom gives since it is a recessive disorder.