Final answer:
Purines, which include adenine and guanine, have two rings in their structure, whereas pyrimidines, which include cytosine, thymine, and uracil (in RNA), have one. The correct answer is b) Purines: 2, Pyrimidines: 1. This difference is essential for DNA structure and base pairing.
Step-by-step explanation:
The question pertaining to the number of rings in purines versus pyrimidines is an important topic in molecular biology. Purines, which include adenine (A) and guanine (G), have a double ring structure comprised of a six-membered ring fused to a five-membered ring. Pyrimidines, which consist of cytosine (C) and thymine (T), and uracil (U) in RNA, have a single ring structure with just a six-membered ring.
The correct answer to the question is: b) Purines: 2, Pyrimidines: 1. So, purines have two rings, while pyrimidines have only one. This structural difference is crucial as it plays a significant role in the formation of DNA base pairs, where purines always pair with pyrimidines (adenine with thymine, and cytosine with guanine) to maintain the DNA double helix structure.