**Core Concept**
Angelman Syndrome is a genetic disorder characterized by developmental delay, intellectual disability, speech impairment, and unique behavioral features. It is caused by a loss of function of the UBE3A gene on chromosome 15, which is normally expressed from the maternal allele.

**Why the Correct Answer is Right**
The correct answer is related to the genetic basis of Angelman Syndrome. The UBE3A gene plays a crucial role in brain development, and its loss of function leads to the characteristic features of the disorder. Specifically, the maternal UBE3A gene is responsible for the expression of the protein, and mutations or deletions of this gene can lead to Angelman Syndrome. The lack of UBE3A function disrupts the normal functioning of the brain, resulting in the symptoms associated with the disorder.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the genetic basis of Angelman Syndrome.
* **Option B:** This option is incorrect because it is a characteristic feature of Prader-Willi Syndrome, not Angelman Syndrome.
* **Option C:** This option is incorrect because it is a characteristic feature of Rett Syndrome, not Angelman Syndrome.
* **Option D:** This option is incorrect because it is a characteristic feature of Fragile X Syndrome, not Angelman Syndrome.

**Clinical Pearl / High-Yield Fact**
Angelman Syndrome is often associated with a characteristic "happy puppet" gait, where the individual has a wide-based gait with a tendency to fall forward.

**Correct Answer:** D. Hypotonia