A female married to a normal male but her father had vitamin D resistant rickets. So what are the chances that her childrens will be colour blind:March 2013
**Core Concept**
Vitamin D-resistant rickets is a rare genetic disorder caused by mutations in the phosphate-regulating genes, including PHEX (phosphate-regulating neutral endopeptidase) and CLCN5. This condition is inherited in an X-linked dominant pattern, primarily affecting females.
**Why the Correct Answer is Right**
The question about the chances of her children being color blind is a red herring, and the correct answer is actually not related to the genetic disorder mentioned. However, based on the given information, we can infer that the mother is a carrier of the vitamin D-resistant rickets gene, which is X-linked. This means the gene is located on the X chromosome.
**Why Each Wrong Option is Incorrect**
* **Option A:** There is no direct correlation between vitamin D-resistant rickets and color blindness. Color blindness is usually inherited in an X-linked recessive pattern, related to genes like OPN1RW and OPN1MW.
* **Option B:** The question does not provide enough information to determine the mother's carrier status for color blindness. However, if the father is normal, it's unlikely that he is a carrier of the color blindness gene.
* **Option C:** This option is not relevant to the given scenario. The genetic disorder mentioned does not affect the color vision genes.
**Clinical Pearl / High-Yield Fact**
In X-linked recessive disorders, such as color blindness, affected males are more common than affected females, as females have two X chromosomes and one normal allele can compensate for the mutated allele.
**Correct Answer:** There is no correct answer provided for this scenario. The question seems to be a distractor.