In an Autosomal Dominant disorder, mother is affected but is heterozygous. Father is normal. What are the chance of disease in children?
## **Core Concept**
An Autosomal Dominant disorder is characterized by the ability of a single copy of a dominant allele to cause the condition. This means if one parent is affected and heterozygous, there's a 50% chance of passing the mutated gene to each offspring.
## **Why the Correct Answer is Right**
In Autosomal Dominant disorders, only one mutated copy of the gene is needed for the disorder to manifest. The mother being heterozygous means she has one normal allele and one disease-causing allele. When determining the chance of disease in children, we consider the probability of inheriting the disease-causing allele from the mother. Since the father is normal, he can only contribute a normal allele. The possible genotypes of the children are 50% chance of inheriting the mutated allele (and thus expressing the disease) and 50% chance of inheriting the normal allele (and thus not expressing the disease). Therefore, there's a 50% chance of each child being affected.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a 0% chance, which would be incorrect for an Autosomal Dominant disorder where one copy of the dominant allele is enough to cause the condition.
- **Option B:** This option suggests a 25% chance, which is typical for Autosomal Recessive disorders when both parents are carriers, not for Autosomal Dominant disorders.
- **Option D:** This option suggests a 100% chance, which would only be true if both parents were affected and the disorder was dominant, or in the case of certain genetic conditions with specific parental genotypes, but not in this scenario.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that in Autosomal Dominant disorders, an affected parent has a 50% chance of passing the mutated gene to each offspring, regardless of the offspring's sex. This is crucial for genetic counseling.
## **Correct Answer:** .