**Core Concept**
Maternal disomy of chromosome 15 refers to a rare genetic condition where a person inherits two copies of chromosome 15 from their mother, instead of the usual one copy from each parent. This occurs due to an error in meiosis or mitosis, resulting in an imbalance of genes on chromosome 15.

**Why the Correct Answer is Right**
Maternal disomy of chromosome 15 is associated with the Prader-Willi syndrome (PWS) and Angelman syndrome (AS). PWS is characterized by severe neonatal hypotonia, poor feeding, and failure to thrive, while AS is marked by severe developmental delay, ataxia, and a happy demeanor. The condition is usually sporadic, but can be inherited in rare cases.

* **Option A:** Imprinting of the UBE3A gene is not related to maternal disomy of chromosome 15.
* **Option B:** Prader-Willi syndrome is associated with paternal deletion or maternal uniparental disomy of chromosome 15, not maternal disomy.
* **Option C:** Angelman syndrome is associated with paternal deletion or maternal uniparental disomy of chromosome 15, not maternal disomy.

**Clinical Pearl / High-Yield Fact**
Maternal disomy of chromosome 15 is a rare cause of Prader-Willi and Angelman syndromes, and genetic counseling is essential for families at risk.

**Correct Answer: D. Prader-Willi and Angelman syndromes**