What evidence did Watson and Crick have at their disposal in 1953? What was their approach in arriving at the structure of DNA?

Key Concepts

Double Helix Structure

Watson and Crick proposed that DNA has a double helix structure, consisting of two intertwined strands. This model explained how genetic information is stored and replicated, with the strands running in opposite directions and held together by complementary base pairing between adenine-thymine and guanine-cytosine.

X-ray Crystallography

X-ray crystallography was a critical technique used by Rosalind Franklin, whose images of DNA provided key insights into its helical structure. Watson and Crick utilized these images, particularly the famous Photo 51, to infer the dimensions and arrangement of the DNA molecule, which was pivotal in their model development.

Base Pairing Rules

The base pairing rules, established by Erwin Chargaff, state that in DNA, the amount of adenine equals thymine, and the amount of guanine equals cytosine. This concept was essential for Watson and Crick as it guided them in understanding how the two strands of DNA are complementary, allowing for accurate replication and transmission of genetic information.