Which one of the following pairs in not correctly matched ?

Options

A. Plasmid - Small piece of extrachromosomal DNA in bacertia
B. Interferon - An enzyme that interferes with DNA replication
C. Cosmid - A vector for carrying large DNA fragments into host cells
D. Myeloma antibodies - Producing tumor cells

Answer

To determine which of the following pairs is not correctly matched, let's analyze each option step by step:

1. **Plasmid**:
- Definition: Plasmids are small, circular pieces of extra chromosomal DNA found in bacteria (prokaryotes) and some eukaryotes.
- Function: They can replicate independently of chromosomal DNA and often carry genes that provide advantages, such as antibiotic resistance.
- Conclusion: The statement "small piece of extra chromosomal DNA in bacteria" is correct.

2. **Interferon**:
- Definition: Interferons are signaling proteins produced by host cells in response to viral infections.
- Function: They play a crucial role in the immune response by interfering with viral replication and activating immune cells.
- Conclusion: The statement "an enzyme that interferes with DNA replication" is incorrect. Interferons are not enzymes; they are proteins that help combat viral infections.

3. **Cosmid**:
- Definition: Cosmids are hybrid vectors that contain features of plasmids and bacteriophages, allowing them to carry larger fragments of DNA.
- Function: They are used in cloning and constructing genomic libraries.
- Conclusion: The statement "vector for carrying large fragments into the host cells" is correct.

4. **Myeloma**:
- Definition: Myeloma cells are a type of cancerous cell derived from plasma cells (a type of white blood cell).
- Function: These cells can produce monoclonal antibodies.
- Conclusion: The statement "antibodies producing tumor cell" is correct as myeloma cells are indeed used to produce antibodies.

After analyzing all options, the pair that is not correctly matched is:

**Interferon: an enzyme that interferes with DNA replication** (this is incorrect).

### Summary of the Correct Answer:
The answer is **Interferon** - it is not an enzyme but a signaling protein involved in the immune response against viruses.