Select the disease which is caused by recessive autosomal genes when present in homozygous condition

Options

A. Alkaptonuria
B. Albinism
C. Cystic Fibrosis
D. All of these

Answer

To solve the question of which disease is caused by recessive autosomal genes when present in a homozygous condition, we can analyze each option provided:

1. **Understanding Autosomal Recessive Disorders**:
- Autosomal recessive disorders are genetic conditions that occur when an individual inherits two copies of a recessive allele (one from each parent). The disease manifests only when the individual is homozygous for the recessive allele, meaning both alleles are the same and recessive.

2. **Evaluating Each Option**:
- **Option A: Alkaptonuria**:
- Alkaptonuria is a metabolic disorder caused by the accumulation of homogentisic acid due to a deficiency in the enzyme homogentisate oxidase. It is inherited in an autosomal recessive manner. Therefore, it is a disease that occurs when the individual is homozygous for the recessive allele.

- **Option B: Albinism**:
- Albinism is characterized by a lack of melanin pigment in the skin, hair, and eyes. It is also inherited in an autosomal recessive manner. Individuals must be homozygous for the recessive allele to express the condition.

- **Option C: Cystic Fibrosis**:
- Cystic fibrosis is a genetic disorder that affects the respiratory and digestive systems. It is caused by mutations in the CFTR gene and is inherited in an autosomal recessive manner. Like the others, it requires homozygosity for the recessive allele to manifest.

- **Option D: All of These**:
- Since all three options (Alkaptonuria, Albinism, and Cystic Fibrosis) are autosomal recessive disorders that require homozygosity for expression, this option is correct.

3. **Conclusion**:
- The correct answer is **D: All of These**.