Question

Urgent, 100 Points

Duchenne muscular dystrophy (DMD) is an X-linked recessive monogenic disorder. Typically, the disease only occurs in boys, who, on average, die before the age of 20. Calculate the probability of a woman having a child with DMD if: (a) her brother has DMD; (b) her mother's brother has DMD; (c) her father's brother has DMD. Provide a solution.

Answer 1

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder, which means that the disease-causing mutation is located on the X chromosome. Since women have two X chromosomes, one of which can compensate for the mutated X chromosome, they are usually carriers of the disease but are not affected by it. Men, on the other hand, only have one X chromosome, so if they inherit the mutated X chromosome, they will develop the disease.

(a) If a woman's brother has DMD, then her mother must be a carrier of the disease. The woman has a 50% chance of inheriting the carrier X chromosome from her mother, and a 50% chance of inheriting the normal X chromosome. If she inherits the carrier X chromosome, she has a 50% chance of passing it on to each of her children. Therefore, the probability of her having a child with DMD is:

0.5 (chance of inheriting carrier X chromosome) × 0.5 (chance of passing on carrier X chromosome) = 0.25 or 25%.

(b) If a woman's maternal uncle has DMD, then her mother must be a carrier of the disease. The woman has a 50% chance of inheriting the carrier X chromosome from her mother, and a 50% chance of inheriting the normal X chromosome. Therefore, the probability of her having a child with DMD is:

0.5 (chance of inheriting carrier X chromosome) × 0.5 (chance of passing on carrier X chromosome) = 0.25 or 25%.

(c) If a woman's paternal uncle has DMD, then her father must be either a carrier or affected by the disease. If her father is a carrier, then the woman has a 50% chance of inheriting the carrier X chromosome from him, and a 50% chance of inheriting the normal X chromosome. If her father is affected by the disease, then he must have inherited the mutated X chromosome from his mother, who was a carrier. The woman has a 50% chance of inheriting the carrier X chromosome from her father's carrier mother, and a 50% chance of inheriting the normal X chromosome. Therefore, the probability of her having a child with DMD is:

0.5 (chance of inheriting carrier X chromosome from carrier father) × 0.5 (chance of passing on carrier X chromosome) + 0.5 (ch

Answer 2

To calculate the probability of a woman having a child with Duchenne muscular dystrophy (DMD) based on specific family scenarios, we need to consider the inheritance pattern and the individuals involved.

DMD is an X-linked recessive disorder, meaning it is caused by a mutation on the X chromosome. Since women have two X chromosomes, they have a higher chance of being carriers of the DMD mutation without necessarily showing symptoms of the disease. Men, on the other hand, have one X and one Y chromosome, so if they inherit the DMD mutation, they are more likely to exhibit symptoms of the disease.

(a) If the woman's brother has DMD:

In this case, the woman is a carrier of the DMD mutation, as her brother has the disease. The probability of her having a child with DMD depends on the inheritance of the X chromosome.

There is a 50% chance that the woman will pass on the DMD mutation to her child if she conceives a son.

There is a 50% chance that the woman will pass on a normal X chromosome to her child if she conceives a daughter.

Therefore, the probability of the woman having a child with DMD is 0.5 or 50% if she conceives a son.

(b) If the woman's mother's brother has DMD:

In this case, the woman's maternal uncle has DMD, indicating that her mother carries the DMD mutation. The woman has a 50% chance of inheriting the DMD mutation from her mother.

If the woman is a carrier, the probability remains the same as in scenario (a). There is a 50% chance of her passing on the DMD mutation to her child if she conceives a son.

(c) If the woman's father's brother has DMD:

In this case, the woman's paternal uncle has DMD, suggesting that her father does not carry the DMD mutation. Since the woman's father does not carry the mutation, the probability of her being a carrier depends on whether her mother is a carrier or has DMD.

If her mother is a carrier, the woman has a 50% chance of inheriting the DMD mutation. The probability remains the same as in scenario (b) if she conceives a son.

If her mother has DMD, the woman herself would have DMD, as it is a monogenic disorder that typically affects boys. In this case, the probability of her having a child with DMD would be 100% regardless of the child's gender.

Step-by-step explanation: