Plasmids are .

Options

A. cDNA
B. mitochondiral DNA
C. circular extrahromosomal DNA in bacteria
D. viral RNA

Answer

### Step-by-Step Text Solution:

1. **Definition of Plasmids**: Plasmids are small, circular, double-stranded DNA molecules that are distinct from the chromosomal DNA found in bacteria. They are considered extrachromosomal DNA because they exist independently of the bacterial chromosome.

2. **Location of Plasmids**: Plasmids are primarily found in bacteria, such as E. coli, but they can also be present in some archaea and eukaryotic organisms. They are not found in the nucleus of eukaryotic cells but can be found in the cytoplasm.

3. **Function of Plasmids**: Plasmids often carry genes that provide bacteria with genetic advantages, such as antibiotic resistance, the ability to metabolize unusual substances, or the production of toxins. They can replicate independently of the bacterial chromosome, allowing for rapid adaptation and survival.

4. **Applications of Plasmids**: Plasmids are widely used in biotechnology and genetic engineering. For example, they are used as vectors to introduce foreign DNA into bacterial cells, which can then produce proteins such as insulin.

5. **Conclusion**: In summary, plasmids are circular extrachromosomal DNA found in bacteria that can replicate independently and carry genes that confer various advantages to the host organism.