Commentary on Watson and Crick Dna Discovery

In their 1953 Nature publication, Watson and Crick announced their landmark discovery: DNA exists in the form of a right handed, three-dimensional double helix. They described their DNA model as two DNA strands connected by hydrogen bonds between complementary bases. Adenine bases are always paired with thymines, and cytosines are always paired with guanines. Watson and Crick identified the anti-parallel configuration of DNA strands; each 5' end of one strand is paired with the 3' end of its complementary strand. Nucleotides are linked to each other by their phosphate groups, which bind the 3' end of one sugar to the 5' end of the next sugar. Nitrogenous bases are available to participate in hydrogen bonding. This important structural feature correlates with function that would soon be discovered: the bases have sites available to form hydrogen bonds with the proteins that play vital roles in the replication and expression of DNA. Since its inception, these features of the Watson and Crick model remain the same today. This enduring credibility is amazing, considering that many scientific research findings are drastically modified over time.

In this paper, the two scientists claim their model to be “radically different” in order to strongly set it apart from the DNA structural model that was competitively proposed by Pauling and Corey, and also by Fraser: a triple helix with bases positioned outward. Watson and Crick rejected the triple helix model, criticizing that the protruding bases would leave the negatively charged phosphates positioned inward and towards each other. This could not be the correct structure because the repulsion of negative charges would blow apart the helix. Therefore, Watson and Crick knew it was the bases, not the phosphates, which were positioned inward and linked by hydrogen bonds. Their structural hypothesis was consistent with Chargaff’s research as well as the x-ray data.

The intrigue of this paper cannot solely be attributed to