A chimeric DNA is formed by

Options

A. Deleting selectable markers
B. Joining c-DNA with plasmid
C. EcoRI
D. Enzyme `beta`- galactosidase

Answer

### Step-by-Step Solution:

1. **Understanding Chimeric DNA**:
- Chimeric DNA is a type of DNA that is composed of fragments from different organisms or different types of DNA. It is often referred to as hybrid DNA.

2. **Relation to Recombinant DNA**:
- Chimeric DNA is similar to recombinant DNA (rDNA) because both contain DNA fragments from different sources. This means that the formation of chimeric DNA involves the combination of DNA from different organisms.

3. **Analyzing the Options**:
- **Option A: Deleting selectable markers**: This option does not contribute to the formation of chimeric DNA. Selectable markers are used in cloning to identify successfully transformed cells, but their deletion does not create chimeric DNA.
- **Option B: Joining cDNA (complementary DNA) with plasmid**: This option is correct. The process of forming chimeric DNA involves isolating DNA (like cDNA) and then inserting it into a plasmid vector. The plasmid acts as a vehicle to replicate the inserted DNA.
- **Option C: E. coli**: This option is incorrect as E. coli is a type of bacteria used in cloning but does not itself form chimeric DNA.
- **Option D: Enzyme beta-galactosidase**: This enzyme is involved in certain cloning processes but does not directly contribute to the formation of chimeric DNA.

4. **Conclusion**:
- The correct answer is **Option B: Joining cDNA or complementary DNA with plasmid**. This process results in the formation of chimeric DNA as the plasmid serves as a vector to carry and replicate the inserted DNA fragment.