During DNA replication discontinuosly synthesized fragments are later joined by the enzyme-

Options

A. Ligase
B. DNA polymerase
C. RNA primer
D. Primase

Answer

**Step-by-Step Solution:**

1. **Understanding DNA Replication**: DNA replication is a semi-conservative process, meaning that each new DNA molecule consists of one old (template) strand and one newly synthesized strand.

2. **Separation of DNA Strands**: The two strands of DNA are separated and unwound by the enzyme helicase, which unwinds the DNA double helix. Topoisomerase also plays a role by relieving the tension created ahead of the replication fork.

3. **Leading and Lagging Strands**: During replication, one strand is synthesized continuously (the leading strand) while the other strand is synthesized in short segments (the lagging strand) due to the antiparallel nature of DNA. The segments on the lagging strand are known as Okazaki fragments.

4. **Synthesis of Okazaki Fragments**: The lagging strand is synthesized in short bursts, creating these Okazaki fragments. Each fragment requires a short RNA primer to initiate synthesis.

5. **Joining Okazaki Fragments**: After the synthesis of Okazaki fragments is complete, these fragments need to be joined together to form a continuous strand. The enzyme responsible for this process is called DNA ligase.

6. **Conclusion**: Therefore, during DNA replication, the discontinuously synthesized fragments (Okazaki fragments) are later joined by the enzyme DNA ligase.

**Final Answer**: The enzyme that joins the discontinuously synthesized fragments during DNA replication is DNA ligase.

---