## **Core Concept**
Maternal disomy of chromosome 15 is associated with Prader-Willi syndrome (PWS), a genetic disorder characterized by severe infantile hypotonia, poor feeding, and failure to thrive, followed by hyperphagia and obesity if not managed properly. This condition results from the loss of function of genes on chromosome 15 inherited from the father. Maternal disomy occurs when a person receives two copies of chromosome 15 from the mother and none from the father.

## **Why the Correct Answer is Right**
Prader-Willi syndrome is caused by the loss of function of genes on the paternal copy of chromosome 15. This can occur through deletion of the paternal chromosome 15, maternal disomy of chromosome 15 (where the individual receives two copies of chromosome 15 from the mother and none from the father), or through an imprinting mutation that silences the paternal genes. The correct answer relates to the scenario where maternal disomy of chromosome 15 leads to the absence of functional paternal genes, resulting in PWS.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not correspond with the known genetic cause of Prader-Willi syndrome.
- **Option B:** This option is incorrect as it does not relate to the condition caused by maternal disomy of chromosome 15.
- **Option D:** This option is incorrect because it is not associated with maternal disomy of chromosome 15.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Prader-Willi syndrome is one of the few conditions associated with maternal uniparental disomy, where the individual inherits two copies of a chromosome from one parent and none from the other. This condition highlights the importance of genomic imprinting in human disease.

## **Correct Answer:** . Prader-Willi syndrome.