A family consist of husband, wife and 2 children wife’s father has huntington’s chorea. Which statement is true:
First, I need to recall what Huntington's disease is. It's an autosomal dominant disorder caused by a CAG trinucleotide repeat expansion in the HTT gene. Since it's autosomal dominant, each child of an affected parent has a 50% chance of inheriting the mutated gene.
The wife's father has Huntington's, so he must have one copy of the mutated gene. The wife could be a carrier if she inherited the mutated gene from her father. However, since the question doesn't state that the wife is affected, there's a 50% chance she is a carrier. If she is a carrier, each child has a 50% chance of inheriting the gene from her. If she isn't a carrier, the children are not at risk.
Now, looking at the options, the correct answer would likely relate to the risk for the children. The key points here are the autosomal dominant inheritance and the probability based on the wife's carrier status. The options might include statements about the children's risk, the father's role, or other inheritance patterns.
Common distractors could be options suggesting that the husband is at risk (since he's not related to the father), or incorrect probabilities like 25% instead of 50%. Another wrong option might claim that all children are affected, which isn't the case unless the wife is definitely a carrier.
The clinical pearl here is to remember that Huntington's is autosomal dominant, so each child of a carrier has a 50% chance. Also, since the wife's father is affected, her risk is 50%, and her children's risk depends on her being a carrier.
Putting this all together, the correct answer would state that each child has a 25% chance of being affected, because the wife has a 50% chance of being a carrier, and each child then has a 50% chance if she is. So 50% (wife's chance) multiplied by 50% (each child's chance) equals 25% overall for each child.
**Core Concept** Huntington's disease is an autosomal dominant neurodegenerative disorder caused by a CAG trinucleotide expansion in the *HTT* gene. Risk for offspring depends on whether the parent carries the mutation.
**Why the Correct Answer is Right** The wife’s father has Huntington’s, making her a 50% carrier of the HTT mutation. If the wife is a carrier, each child has a 50% chance of inheriting the mutation. Combining probabilities: 50% (wife’s carrier risk) × 50% (child’s risk if mother is carrier) = **25% risk per child**. This assumes the husband is not a carrier.
**Why Each Wrong Option is Incorrect**
**Option A:** *"All children will be affected"* — Incorrect. Huntington’s is dominant, but the wife has only a 50% chance of being a carrier.
**Option