Mutation in PKHD1 gene causing autosomal recessive polycystic kidney disease (ARPKD) maps to which chromosome?

**Core Concept:** Autosomal Recessive Polycystic Kidney Disease (ARPKD) is a genetic disorder caused by mutations in PKHD1 gene. PKHD1 (Polycystic Kidney Disease 1) is a protein involved in ciliogenesis (formation of cilia and flagella) and cell signaling pathways. The disease is characterized by cyst formation in the liver and kidneys, leading to impaired organ function and failure.

**Why the Correct Answer is Right:** ARPKD is an autosomal recessive disorder, meaning both parents must be carriers of the mutated PKHD1 gene for their child to be affected. The PKHD1 gene is located on chromosome 6 (6p21.3). The correct answer (C) refers to the specific chromosome where the mutation occurs, thus making it the correct choice.

**Why Each Wrong Option is Incorrect:**

A. Chromosome 1 (1p34.2) is incorrect because it does not contain the PKHD1 gene.
B. Chromosome 19 (19p13.3) is incorrect because it does not contain the PKHD1 gene.
D. Chromosome 22 (22q13.3) is incorrect because it does not contain the PKHD1 gene.

**Clinical Pearl / High-Yield Fact:** Understanding the location of genes and genetic disorders on chromosomes is essential for genetic counseling and prenatal diagnosis. In cases of consanguineous marriages, parents are more likely to be carriers of recessive disorders like ARPKD, and testing can confirm the diagnosis and inform medical management.

**Correct Answer:** C. Chromosome 6 (6p21.3)