In cloning experiments cDNA molecules can be obtained from an mRNA copy by

Options

A. Polymerase chain reaction
B. Reverse transcriptase
C. Ribozyme
D. DNA-RNA hybridisation.

Answer

To solve the question regarding how cDNA molecules can be obtained from an mRNA copy in cloning experiments, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding cDNA**:
- cDNA stands for complementary DNA. It is a form of DNA that is synthesized from a messenger RNA (mRNA) template.

2. **Role of mRNA**:
- mRNA is a type of RNA that carries the genetic information from DNA to the ribosome, where proteins are synthesized.

3. **Reverse Transcription Process**:
- The process of synthesizing cDNA from mRNA is known as reverse transcription. This is the reverse of the transcription process, where RNA is synthesized from a DNA template.

4. **Enzyme Involved**:
- The key enzyme that facilitates the conversion of mRNA to cDNA is called reverse transcriptase. This enzyme synthesizes the cDNA strand by using the mRNA as a template.

5. **Conclusion**:
- Therefore, in cloning experiments, cDNA molecules can be obtained from an mRNA copy specifically by using reverse transcriptase.

### Final Answer:
The correct option is **reverse transcriptase**.