Which kind of erizymes join two molecules together?

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the type of enzymes that are responsible for joining two molecules together.

2. **Identifying the Enzyme**: The enzyme that performs this function is called **Ligase**. Ligases are specialized enzymes that catalyze the joining of two molecules.

3. **Mechanism of Action**: Ligases work by creating **covalent bonds** between the two molecules. This is crucial in various biological processes, including DNA replication and repair.

4. **Specific Example**: A common example of ligase activity is seen with **DNA ligase**, which joins two DNA molecules by forming **phosphodiester bonds**. This is particularly important during DNA replication and repair processes.

5. **Functionality**: Ligases fill in the gaps between nucleotides in DNA, ensuring that the DNA strand is continuous and intact.

6. **Limitations**: It is important to note that ligases cannot be used effectively on **blunt ends** of DNA fragments. Blunt ends are produced when DNA is cut by restriction endonucleases, and ligases require overhanging ends to function properly.

7. **Conclusion**: Therefore, the answer to the question is that the enzyme responsible for joining two molecules together is **Ligase**.