Single gene autosomal recessive disease is
**Core Concept**
Single gene autosomal recessive diseases are caused by mutations in a single gene and are inherited in an autosomal recessive pattern, meaning an individual must inherit two copies of the mutated gene (one from each parent) to express the disease. This pattern of inheritance affects both males and females equally. Examples include **cystic fibrosis** and **sickle cell anemia**.
**Why the Correct Answer is Right**
Although the specific correct answer is not provided, a common example of a single gene autosomal recessive disease is **cystic fibrosis**, caused by mutations in the **CFTR gene**. This disease manifests due to the accumulation of thick, sticky mucus that clogs the airways and traps bacteria, resulting in recurrent respiratory infections and other complications. The disease is expressed only when an individual is homozygous recessive for the mutated gene.
**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific answer choices, it's challenging to provide detailed explanations for each incorrect option. However, in general, incorrect options for single gene autosomal recessive diseases might include diseases that are autosomal dominant, X-linked, or multifactorial.
**Option B:** Similarly, without specific details, we can speculate that this option might be incorrect if it represents a disease with a different mode of inheritance.
**Option C:** This option could be incorrect if it describes a condition that does not fit the criteria for a single gene autosomal recessive disease.
**Option D:** This might be an option that is not relevant to single gene autosomal recessive diseases.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that carriers of autosomal recessive diseases (who have one normal and one mutated gene) are usually asymptomatic but can pass the mutated gene to their offspring. This has significant implications for **genetic counseling**.
**Correct Answer:** Correct Answer: D. Cystic Fibrosis