Retinoblastoma is associated with which chromosome?

**Core Concept**
Retinoblastoma is a malignant tumor of the retina, often presenting in children. It is a prototype for understanding the relationship between genetic mutations and cancer development. The disease is associated with a specific genetic locus, making it a classic example of a hereditary cancer syndrome.

**Why the Correct Answer is Right**
Retinoblastoma is caused by mutations in the RB1 gene, which is located on the long arm of chromosome 13 (13q14). The RB1 gene acts as a tumor suppressor, regulating the cell cycle and preventing uncontrolled cell division. Mutations in this gene lead to the loss of its tumor suppressor function, resulting in the development of retinoblastoma. The disease can be inherited in an autosomal dominant pattern, meaning that a single copy of the mutated gene is sufficient to increase the risk of developing retinoblastoma.

**Why Each Wrong Option is Incorrect**
**Option A:** Chromosome 3 is associated with von Hippel-Lindau syndrome, which is another hereditary cancer syndrome, but not retinoblastoma.
**Option B:** Chromosome 17 is associated with the p53 gene, which is also a tumor suppressor gene, but mutations in p53 are associated with Li-Fraumeni syndrome, not retinoblastoma.
**Option C:** Chromosome 22 is associated with neurofibromatosis type 2, which is a different hereditary tumor syndrome.

**Clinical Pearl / High-Yield Fact**
Retinoblastoma is one of the few cancers that can be diagnosed prenatally, and genetic testing can identify individuals with a high risk of developing the disease. Early detection and treatment are critical for improving outcomes in retinoblastoma.

**Correct Answer: C. 13**