A Particular genetic disorder appears in three consecutive generations of a family without any sex predilection. It was also noticed that phenotypically normal family members were having healthy offspring, What is the pattern of inheritance of this disorder ?
## Core Concept
The question describes a genetic disorder that appears in three consecutive generations of a family without any sex predilection. This pattern suggests an autosomal dominant mode of inheritance, where a single copy of the dominant allele is enough to cause the condition. The fact that phenotypically normal family members have healthy offspring also provides clues about the inheritance pattern.
## Why the Correct Answer is Right
The disorder's appearance in three consecutive generations without sex predilection is characteristic of **autosomal dominant inheritance**. In autosomal dominant disorders, an affected individual has a 50% chance of passing the mutated gene to each offspring. The fact that phenotypically normal family members have healthy offspring suggests that they are unlikely to be carriers of an autosomal recessive condition (which would require two copies of the mutated gene to express the disease) or to be affected in a sex-linked pattern. This pattern fits with **autosomal dominant** inheritance because an individual only needs to inherit one copy of the dominant allele to express the disorder.
## Why Each Wrong Option is Incorrect
- **Option A:** This option would represent an **autosomal recessive** pattern. This is incorrect because autosomal recessive disorders typically require both parents to be at least carriers, and there's a 25% chance each offspring will be affected, 50% chance will be carriers, and 25% chance will be neither affected nor carriers. The scenario provided doesn't specify carrier status or the offspring distribution.
- **Option B:** This option suggests a **sex-linked** (or X-linked) pattern. This is incorrect because sex-linked disorders show a predilection for one sex over the other (typically males are more frequently affected than females in X-linked recessive conditions). The question explicitly states there is no sex predilection.
- **Option D:** Without a description provided for option D, we assume it does not fit the description of autosomal dominant inheritance based on the elimination of other options.
## Clinical Pearl / High-Yield Fact
A key point to remember is that in **autosomal dominant** conditions, every generation is typically affected, and there is no sex predilection. An affected individual has a 50% chance of passing the condition to each child. This is different from **autosomal recessive** conditions, where two carrier parents have a 25% chance of having an affected child.
## Correct Answer: C.