**Core Concept**
The retinoblastoma gene (RB1) is a tumor suppressor gene that plays a crucial role in regulating the cell cycle and preventing uncontrolled cell growth. It is involved in the pathogenesis of retinoblastoma, a malignant tumor of the retina.

**Why the Correct Answer is Right**
The RB1 gene is located on the long arm of chromosome 13 (13q14). It encodes a protein that binds to and inhibits the activity of the E2F transcription factor, thereby regulating the expression of genes involved in cell cycle progression. The loss of RB1 function due to mutations or deletions of the gene leads to uncontrolled cell growth and tumor formation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect, as the RB1 gene is not located on chromosome 1.
**Option B:** This option is incorrect, as the RB1 gene is not located on chromosome 2.
**Option C:** This option is incorrect, as the RB1 gene is not located on chromosome 11.

**Clinical Pearl / High-Yield Fact**
Retinoblastoma is a rare but aggressive tumor that typically affects young children, and early detection and treatment are crucial for improving outcomes. The RB1 gene is also involved in other types of cancer, including osteosarcoma and bladder cancer.

**Correct Answer:** D. 13q14