**Core Concept**
The RB (Retinoblastoma) gene is a tumor suppressor gene that plays a crucial role in regulating the cell cycle and preventing uncontrolled cell growth. It is a classic example of a gene that, when mutated, can lead to cancer. The RB gene is involved in the G1 to S phase transition of the cell cycle, where it binds to and inhibits the E2F transcription factor.

**Why the Correct Answer is Right**
The RB gene is located on the long arm (q) of chromosome 13 (13q14.2). This is a critical piece of information in the field of medical genetics, as mutations in the RB gene can lead to retinoblastoma, a type of eye cancer that typically affects children. The RB gene works by binding to the E2F transcription factor, which is necessary for the cell to progress from the G1 phase to the S phase of the cell cycle. When the RB gene is mutated, the E2F transcription factor is no longer inhibited, leading to uncontrolled cell growth and cancer.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the RB gene is not located on chromosome 1.
**Option B:** This option is incorrect because the RB gene is not located on chromosome 5.
**Option C:** This option is incorrect because the RB gene is not located on chromosome 18.

**Clinical Pearl / High-Yield Fact**
The RB gene is a classic example of a tumor suppressor gene, and its mutation can lead to cancer. This is a high-yield fact for medical students, as understanding the genetics behind cancer is critical for understanding the disease and developing effective treatments.

**Correct Answer:** D. The RB gene is located on chromosome 13 (13q14.2).