Disease having autosomal recessive inheritance -a) Cystic fibrosisb) Hydrocephalusc) Duchene muscular dystrophyd) Albinisme) Vitamin D resistant ricket

**Core Concept**
Autosomal recessive inheritance refers to a pattern of inheritance where a disease-causing gene mutation occurs on one of the two copies of a gene (one inherited from each parent). This results in a condition that typically manifests in individuals who are homozygous recessive for the mutated gene, meaning they have two copies of the mutated gene (one from each parent).

**Why the Correct Answer is Right**
Cystic fibrosis is a classic example of an autosomal recessive disorder caused by mutations in the CFTR gene, which encodes for a chloride channel. This mutation disrupts the normal functioning of the chloride channel, leading to abnormal mucus production and respiratory complications. The disease is characterized by symptoms such as respiratory infections, digestive issues, and pancreatic insufficiency. The autosomal recessive pattern of inheritance means that individuals with cystic fibrosis are homozygous recessive for the mutated gene.

**Why Each Wrong Option is Incorrect**
**Option A:** Cystic fibrosis is the correct answer, so this option is incorrect by definition.
**Option B:** Hydrocephalus is a condition characterized by an accumulation of cerebrospinal fluid in the brain, leading to increased intracranial pressure. It is not typically an autosomal recessive disorder.
**Option C:** Duchenne muscular dystrophy is an X-linked recessive disorder caused by mutations in the dystrophin gene, making it a less likely candidate for an autosomal recessive inheritance pattern.
**Option D:** Albinism is a group of disorders characterized by a reduction or absence of melanin production, and it can be inherited in an autosomal recessive pattern, but it is not as commonly associated with this pattern as cystic fibrosis.

**Clinical Pearl / High-Yield Fact**
Cystic fibrosis is the most common life-shortening autosomal recessive disorder, with over 70,000 individuals affected worldwide. It is essential for clinicians to be aware of the genetic basis of cystic fibrosis to provide accurate genetic counseling and management.

**Correct Answer:** C. Cystic fibrosis