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

Options

A. (a) Alkaptonuria
B. (b) Albinism
C. (c) Cystic fibrosis
D. (d) all of these

Answer

To solve the question regarding the disease caused by recessive autosomal genes when present in homozygous condition, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Autosomal Recessive Inheritance**:
- Autosomal recessive diseases are caused by mutations in genes located on autosomes (non-sex chromosomes).
- For a person to express an autosomal recessive trait, they must inherit two copies of the recessive allele (homozygous condition).

2. **Identifying Characteristics of Autosomal Recessive Diseases**:
- These diseases often do not manifest in the parents, as they can be carriers (heterozygous) without showing symptoms.
- The affected offspring can appear in a pedigree chart where parents are typically unaffected but both are carriers.

3. **Analyzing the Pedigree Chart**:
- In a pedigree chart, if only one child is affected and both parents are unaffected, it suggests that both parents are heterozygous carriers of the recessive allele.

4. **Reviewing the Options**:
- The question provides multiple options that may include various genetic disorders.
- We need to determine which of these disorders are known to be caused by recessive autosomal genes.

5. **Selecting the Correct Answer**:
- After reviewing the options and understanding that all listed diseases are classified as autosomal recessive disorders, we conclude that the correct answer is that all of these diseases are caused by recessive autosomal genes when present in homozygous condition.

### Final Answer:
The correct answer is **D) All of these**.