Which of the following is not X linked recessive?
**Core Concept**
X-linked recessive inheritance refers to a pattern of inheritance where a genetic disorder is caused by mutations on the X chromosome, and predominantly affects males, who have only one X chromosome. Females can be carriers of these disorders or express them in a milder form due to X-chromosome inactivation.
**Why the Correct Answer is Right**
X-linked recessive disorders typically affect males because they have only one X chromosome. If the X chromosome carries a mutation, the male will express the disorder. Females, on the other hand, have two X chromosomes, which allows them to compensate for the mutated gene by inactivating the other X chromosome. This means that females are often carriers of X-linked recessive disorders.
**Why Each Wrong Option is Incorrect**
**Option A:** This disorder is indeed X-linked recessive, as it primarily affects males and is caused by mutations on the X chromosome.
**Option B:** This condition is also X-linked recessive, as it predominantly affects males and is due to mutations on the X chromosome.
**Option C:** This disorder is not X-linked recessive; it is instead inherited in an autosomal dominant pattern, meaning one copy of the mutated gene is enough to cause the condition.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that X-linked recessive disorders often have a higher incidence in populations with a higher frequency of carrier females. This is because carrier females can pass the mutated gene to their offspring, increasing the risk of the disorder.
**Correct Answer: C. This disorder is not X-linked recessive; it is instead inherited in an autosomal dominant pattern, meaning one copy of the mutated gene is enough to cause the condition.**