Which of the following is x-linked recessive –
**Core Concept**
The question is asking about a genetic disorder that follows an X-linked recessive pattern of inheritance. This means that the affected gene is located on the X chromosome, and the disorder primarily affects males, who have only one X chromosome. Females can be carriers of the disorder, as they have two X chromosomes, and may exhibit mild symptoms or be asymptomatic.
**Why the Correct Answer is Right**
X-linked recessive disorders are caused by mutations in genes on the X chromosome. In males, who have only one X chromosome, a mutation in an essential gene can lead to the development of the disorder, as they do not have a second X chromosome to compensate. In females, who have two X chromosomes, a mutation in one X chromosome can be compensated by the normal gene on the other X chromosome, resulting in mild or absent symptoms. Examples of X-linked recessive disorders include hemophilia A and B, and Duchenne muscular dystrophy.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not provide a specific example of an X-linked recessive disorder. While it may be a genetic disorder, it does not follow the X-linked recessive pattern of inheritance.
* **Option B:** This option is incorrect because it is a genetic disorder that follows an autosomal dominant pattern of inheritance. Autosomal dominant disorders can affect both males and females, and only one copy of the mutated gene is needed to develop the disorder.
* **Option C:** This option is incorrect because it is a genetic disorder that follows an autosomal recessive pattern of inheritance. Autosomal recessive disorders can affect both males and females, and two copies of the mutated gene (one from each parent) are needed to develop the disorder.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that X-linked recessive disorders primarily affect males, while females are often carriers. This is because males have only one X chromosome, making them more susceptible to the effects of a mutated gene. Females, on the other hand, have two X chromosomes, which can compensate for a mutated gene on one X chromosome.
**Correct Answer: C. Becker muscular dystrophy**