NOR is characterised by the presence of abundant

Options

A. Pseudogenes
B. Repetitive DNA
C. Repeated genes
D. Multigene family giving rise to different RNAs at different times.

Answer

To answer the question "NOR is characterised by the presence of abundant," we need to analyze the options and understand what NOR (Nucleolus Organizer Regions) entails.

### Step-by-Step Solution:

1. **Understanding NOR**:
- NOR stands for Nucleolus Organizer Regions. These are specific regions on chromosomes that play a crucial role in the formation of the nucleolus, which is essential for ribosome biogenesis.

2. **Identifying the Characteristics of NOR**:
- NORs are known to contain tandem copies of ribosomal DNA (rDNA) genes. This means that they have multiple copies of the genes that code for ribosomal RNA, which is a key component of ribosomes.

3. **Analyzing the Options**:
- **Pseudogenes**: These are non-functional sequences that resemble functional genes but do not produce functional products.
- **Repetitive DNA**: This refers to sequences that are repeated multiple times in the genome. NORs contain repetitive sequences, specifically the rDNA.
- **Repeated Genes**: This could refer to genes that are present in multiple copies, which is somewhat similar to rDNA but is not specific to the context of NOR.
- **Multi-gene Family**: This refers to a group of related genes that arise from a common ancestor and typically have similar functions. While rDNA can be considered a multi-gene family, the term "repetitive DNA" is more encompassing in this context.

4. **Conclusion**:
- Given that NORs are characterized by the presence of ribosomal DNA, which is a form of repetitive DNA, the correct answer to the question is **repetitive DNA**.

### Final Answer:
NOR is characterised by the presence of abundant **repetitive DNA**.