purine : guanine : : pyrimidine : ………………

Explanation

To solve the analogy "purine : guanine :: pyrimidine : ...", we need to identify the relationship between the first two terms and apply it to the second pair.

1. **Identify the first pair**: The first term is "purine" and the second term is "guanine".
- Purines are a type of nitrogenous base found in nucleic acids, and guanine is one of the examples of purines.

2. **Identify the category of the second term**: The second term in the analogy is "pyrimidine".
- Pyrimidines are another type of nitrogenous base, distinct from purines.

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