Which scientists proposed the double helix structure of DNA and helped explain replication?

• A. The discovery of RNA
• B. Watson and Crick
• C. The process of transcription
• D. The concept of natural selection

Answer: (B)

The main idea is that Watson and Crick proposed the double-helix model of DNA, and that view explains how replication works. Their model shows two long strands wrapped into a helix with the bases pairing in the middle—adenine with thymine and guanine with cytosine. This complementary pairing means the strands can unzip and each strand can serve as a template to build a new partner strand, producing two identical DNA molecules in a semi-conservative manner. The idea was supported by Chargaff’s rules and the X-ray data from Rosalind Franklin and Maurice Wilkins, which helped reveal the helix shape and dimensions. The other options don’t identify the scientists who proposed the structure or a related mechanism: discovering RNA is not about proposing the DNA shape; transcription and natural selection describe processes or concepts, not the structural model.