Repeated gene are common in case of

Options

A. rRNA
B. Globin genes
C. Pleistropy
D. Cystic fibrosis.

Answer

### Step-by-Step Solution:

1. **Understanding Repeated Genes**:
- Repeated genes are sequences of DNA that occur multiple times within the genome. They are often found in clusters and can be easily identified due to their repetitive nature.

2. **Identifying the Function of Repeated Genes**:
- These genes utilize a unique gene amplification system to maintain their copy number. This is particularly important because during recombination (which occurs in meiosis), the number of these genes can be reduced.

3. **Evaluating the Options**:
- **Option 1: rRNA**: Ribosomal RNA (rRNA) genes are known to be highly repeated in the genome. They play a crucial role in protein synthesis and are typically found in multiple copies.
- **Option 2: Globin Genes**: These genes are responsible for encoding globin proteins, which are part of hemoglobin. They do not exhibit the same level of repetition as rRNA genes.
- **Option 3: Dystrophy**: This term likely refers to muscular dystrophy, which is a genetic disorder but does not pertain to repeated genes.
- **Option 4: Cystic Fibrosis**: This is a genetic disorder caused by mutations in a single gene and does not involve repeated genes.

4. **Conclusion**:
- After evaluating all the options, it is clear that repeated genes are most commonly associated with rRNA. Therefore, the correct answer is **Option 1: rRNA**.