Which of the following is incorrect match?

Options

A. Gene therapy : An abnormal gene is replaced by normal gene
B. Cloning : Ability to multiply copies of antibiotic resistance gene in E. coli
C. Restriction enzymes : Molecular scissors
D. Exonucleases : Molecular glue

Answer

To solve the question "Which of the following is incorrect match?", we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand Gene Therapy**:
- Gene therapy involves replacing an abnormal gene with a normal gene. This is a correct statement.
- **Conclusion**: This option is correct.

2. **Analyze Cloning**:
- Cloning refers to the ability to produce identical copies of an organism or a gene. The statement mentions the ability to multiply copies of an antibiotic resistance gene in E. coli, which is a valid example of cloning.
- **Conclusion**: This option is also correct.

3. **Examine Restriction Enzymes**:
- Restriction enzymes, also known as endonucleases, act as molecular scissors that cut DNA at specific sites. This description is accurate.
- **Conclusion**: This option is correct.

4. **Evaluate Exonucleases**:
- Exonucleases are enzymes that remove nucleotides from the ends of a DNA molecule. The statement claims that exonucleases are molecular glue. This is incorrect because molecular glue refers to ligases, which join DNA fragments together, while exonucleases do not perform this function.
- **Conclusion**: This option is incorrect.

### Final Answer:
The incorrect match is: **Exonucleases are molecular glue**.