Sticky ends, observed in the DNA , are due to the action of a particular type of nucleases. Which of the following statements is correct regarding the sticky ends of the DNA strand ?

Options

A. The sticky ends are made of unpaired nucleotides
B. The sticky ends have an adhesive group for attachment.
C. The sticky ends are made of paired up nucleotides
D. The sticky ends are made by the action of ligases

Answer

To solve the question regarding the sticky ends observed in DNA and identify the correct statement about them, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Sticky Ends**:
- Sticky ends are the short, single-stranded overhangs at the ends of a DNA molecule that result from the action of restriction enzymes (nucleases). These ends can easily pair with complementary sequences of DNA.

**Hint**: Remember that sticky ends are formed due to the cleavage of DNA by restriction enzymes.

2. **Analyzing the Options**:
- **Option 1**: "Sticky ends are made of unpaired nucleotides."
- This statement is correct. Sticky ends consist of unpaired nucleotides that can base pair with complementary sequences.

- **Option 2**: "Sticky ends have an adhesive group for attachment."
- This statement is incorrect. While sticky ends can bind to complementary DNA sequences, they do not have a specific adhesive group; they rely on base pairing.

- **Option 3**: "Sticky ends are made of paired nucleotides."
- This statement is incorrect. Sticky ends are characterized by their unpaired nature, which allows them to interact with other DNA strands.

- **Option 4**: "Sticky ends are made by the action of ligases."
- This statement is incorrect. Sticky ends are formed by restriction enzymes, not ligases. Ligases are responsible for joining DNA fragments together.

3. **Conclusion**:
- The correct answer is **Option 1**: "Sticky ends are made of unpaired nucleotides."

### Summary of the Correct Answer:
- Sticky ends are indeed made up of unpaired nucleotides, allowing them to easily anneal to complementary DNA strands, which is essential in molecular cloning and genetic engineering.