Which of the following Trinucleotide repeat mutation is present in Huntington’s disease?
**Core Concept**
Huntington's disease is a neurodegenerative disorder caused by an expansion of a trinucleotide repeat mutation in a specific gene. This genetic mutation leads to the degeneration of neurons in the brain, particularly in the basal ganglia, resulting in motor, cognitive, and psychiatric symptoms.
**Why the Correct Answer is Right**
The correct answer is a trinucleotide repeat mutation of CAG in the Huntingtin gene (HTT). This mutation causes an expansion of a polyglutamine tract in the Huntingtin protein, leading to protein misfolding and aggregation. The pathogenesis of Huntington's disease is thought to be related to the gain-of-toxic-function of the mutant Huntingtin protein, which disrupts normal cellular processes and leads to neuronal death.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the correct trinucleotide repeat mutation associated with Huntington's disease.
* **Option B:** This option is incorrect because it mentions a different trinucleotide repeat mutation, which is not associated with Huntington's disease.
* **Option D:** This option is incorrect because it is not a trinucleotide repeat mutation, and it is not associated with Huntington's disease.
**Clinical Pearl / High-Yield Fact**
Huntington's disease is an autosomal dominant disorder, meaning that a single copy of the mutated gene is sufficient to cause the disease. This is an important clinical correlation to remember, as it highlights the potential for genetic transmission of the disease.
**Correct Answer:** C. CAG.