Substitution of a purine nucleotide by pyrimidine nucleotide is called

Options

A. transition
B. transversion
C. inversion
D. transduction

Answer

**Step-by-Step Solution:**

1. **Understanding Nucleotide Types**:
- Nucleotides are the building blocks of DNA and RNA. They consist of a sugar, a phosphate group, and a nitrogenous base. The nitrogenous bases are categorized into two groups: purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil).

2. **Identifying the Substitution**:
- The question specifically refers to the substitution of a purine nucleotide (adenine or guanine) with a pyrimidine nucleotide (cytosine, thymine, or uracil).

3. **Defining the Process**:
- The substitution of one type of nucleotide for another can lead to different types of mutations. In this case, when a purine is replaced by a pyrimidine, it is termed a "transversion."

4. **Conclusion**:
- Therefore, the substitution of a purine nucleotide by a pyrimidine nucleotide is called a "transversion."

**Final Answer**: The substitution of a purine nucleotide by a pyrimidine nucleotide is called a transversion.

---