The gene responsible for Ataxia Telangiectasia is located on:
**Core Concept**
Ataxia Telangiectasia (AT) is a rare, inherited disorder characterized by progressive cerebellar ataxia, telangiectasias, immunodeficiency, and a heightened risk of cancer. The disease is caused by mutations in a specific gene involved in DNA repair and replication.
**Why the Correct Answer is Right**
The gene responsible for Ataxia Telangiectasia is ATM (Ataxia-Telangiectasia Mutated). The ATM gene encodes a protein kinase that plays a crucial role in the activation of cell cycle checkpoints and DNA repair pathways, particularly in response to double-strand breaks. When the ATM gene is mutated, cells are unable to properly repair DNA damage, leading to the accumulation of mutations and the characteristic symptoms of AT. The ATM gene is located on chromosome 11q22.3.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the gene responsible for Ataxia Telangiectasia is not located on chromosome 2.
**Option B:** This option is incorrect because the gene responsible for Ataxia Telangiectasia is not located on chromosome 21.
**Option D:** This option is incorrect because the gene responsible for Ataxia Telangiectasia is not located on chromosome 7.
**Clinical Pearl / High-Yield Fact**
Ataxia Telangiectasia is an autosomal recessive disorder, meaning that patients must inherit two copies of the mutated ATM gene (one from each parent) to express the disease. Patients with one copy of the mutated gene are typically asymptomatic but may be at increased risk of cancer.
**Correct Answer: C. 11q22.3**