Which type of primer is used the genetic engineering tool -polymerase chain Reaction?

Options

A. Complementary to 5 ' end of DNA and template
B. Complementary to 3 ' end of DNA and template
C. Complementary to both 3' and 5' end of DNA template
D. Complementary to each other

Answer

To solve the question "Which type of primer is used in the genetic engineering tool - polymerase chain reaction (PCR)?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of Primers in PCR**:
- Primers are short single-stranded DNA sequences that are essential for the polymerase chain reaction. They provide a starting point for DNA synthesis.

2. **Identify the Characteristics of Primers**:
- Primers must be complementary to the target DNA sequence. They anneal (bind) to the template DNA to initiate replication.

3. **Analyze the Options**:
- **Option 1**: Complementary to the fifth end of the DNA template.
- This option is incorrect because primers bind to the 3' end of the DNA template.
- **Option 2**: Complementary to the third end of the DNA template.
- This option is correct because primers indeed bind to the 3' end of the DNA template.
- **Option 3**: Complementary to both third and the fifth end of the DNA template.
- This option is incorrect as primers do not bind to both ends.
- **Option 4**: Complementary to each other.
- This option is incorrect because primers are designed to bind to the template DNA, not to each other.

4. **Conclusion**:
- The correct answer is **Option 2**: Primers used in PCR are complementary to the 3' end of the DNA template.