**Core Concept**
The PKD1 gene is a crucial gene involved in the pathogenesis of Autosomal Dominant Polycystic Kidney Disease (ADPKD). Polycystin-1, the protein product of PKD1, plays a significant role in maintaining the structural integrity of the renal tubules and regulating cell-cell and cell-matrix interactions.

**Why the Correct Answer is Right**
The PKD1 gene is located on chromosome 16. This gene encodes the polycystin-1 protein, which is a large transmembrane protein that functions as a receptor for extracellular calcium and other signaling molecules. Mutations in the PKD1 gene disrupt normal cellular function, leading to the formation of numerous fluid-filled cysts in the kidneys, characteristic of ADPKD.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as the PKD1 gene is not located on chromosome 1.
* **Option B:** This option is incorrect as the PKD1 gene is not located on chromosome 2.
* **Option D:** This option is incorrect as the PKD1 gene is not located on chromosome 20.

**Clinical Pearl / High-Yield Fact**
ADPKD is a common cause of end-stage renal disease, and early detection through genetic testing can help in monitoring disease progression and planning appropriate management strategies.

**Correct Answer:** C. 16.