**Core Concept**
Patau syndrome is a genetic disorder caused by a chromosomal abnormality. It is characterized by an extra copy of **chromosome 13**, leading to severe intellectual disability and physical abnormalities. This condition is also known as **trisomy 13**.

**Why the Correct Answer is Right**
The correct answer is related to **trisomy 13**, which occurs when there is an extra copy of chromosome 13. This extra genetic material disrupts normal development, leading to severe physical and intellectual disabilities. The **mechanism** involves **nondisjunction** during meiosis, resulting in an extra chromosome 13 in every cell.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not correspond to the description of Patau syndrome.
**Option B:** This option is also incorrect as it does not relate to **trisomy 13**.
**Option D:** Similarly, this option is incorrect because it is not associated with Patau syndrome.

**Clinical Pearl / High-Yield Fact**
Patau syndrome has a poor prognosis, with most affected individuals dying in infancy. It is essential to recognize the clinical features, including **microphthalmia**, **polydactyly**, and **cleft lip/palate**, to provide appropriate genetic counseling.

**Correct Answer:** D. Trisomy 13