Assertion: Origin of replication is an essential part of a vector.
Reason: Ori is responsible for initiating replication.

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true and R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that the origin of replication (Ori) is an essential part of a vector. A vector is a DNA molecule used to deliver genetic material into a host cell.

2. **Understanding the Reason**: The reason provided is that the origin of replication is responsible for initiating replication. This means that without the Ori, the process of DNA replication cannot begin.

3. **Role of the Origin of Replication**: The Ori is a specific sequence of DNA that signals the cellular machinery to start the replication process. It is crucial for the replication of the vector once it is inside a host cell.

4. **Importance of Ori in Vectors**: For any vector to replicate within a host cell, it must have an origin of replication. Without this sequence, the vector cannot be copied, and thus, it cannot propagate the genetic material it carries.

5. **Conclusion**: Since the assertion correctly identifies the importance of Ori in vectors and the reason accurately explains why Ori is essential (it initiates replication), both the assertion and reason are true, and the reason is a correct explanation of the assertion.

**Final Answer**: Both the assertion and reason are true, and the reason is the correct explanation of the assertion.

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