Substitution of a purine base with a pyrimidine base or vice versa is called

Options

A. Transition
B. Transversion
C. Deletion
D. Addition

Answer

To solve the question regarding the substitution of a purine base with a pyrimidine base or vice versa, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Purines**: These are nitrogenous bases that include adenine (A) and guanine (G).
- **Pyrimidines**: These are nitrogenous bases that include cytosine (C), thymine (T), and uracil (U).

2. **Identify the Type of Substitution**:
- The question asks about the substitution of a purine with a pyrimidine or a pyrimidine with a purine. This is a specific type of mutation.

3. **Differentiate Between Types of Mutations**:
- **Transition**: This is a mutation where a purine is substituted for another purine or a pyrimidine for another pyrimidine.
- **Transversion**: This is a mutation where a purine is substituted for a pyrimidine or vice versa.

4. **Apply the Definitions to the Question**:
- Since the question specifically mentions the substitution of a purine base with a pyrimidine base or the other way around, we are looking for the term that describes this type of mutation.

5. **Conclude with the Correct Term**:
- The correct term for the substitution of a purine base with a pyrimidine base or vice versa is **transversion**.

### Final Answer:
The substitution of a purine base with a pyrimidine base or vice versa is called **transversion**.

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