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Watson & Crick and the Discovery of the Double Helix

written by: Emma Lloyd•edited by: Leigh A. Zaykoski•updated: 10/21/2011

How did the discovery of the structure of DNA come about, and what steps led to this discovery?

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    Few discoveries have been more significant than that in which James Watson and Francis Crick determined the structure of DNA. But there’s more to the discovery than the work they did, and the story actually began several decades earlier.

    In 1928, a scientist by the name of Frederick Griffith discovered transformation, a process in which cells ingest foreign DNA, incorporate into their own genomes, and then express it. Griffith made this discovery after realizing that genetic information could be transferred from dead bacteria to living bacteria.

    However, it was not until 1944, that a group of researchers discovered that the molecule which would become known as DNA was the responsible for this transfer. At the time, scientists were divided as to whether it was DNA or protein which carried genetic information. Finally, the Hershey-Chase experiments in 1952, in which bateriophages were used to transmit genetic information, provided confirmation that DNA was the relevant molecule.

    In 1953, James Watson and Francis Crick determined the structure of DNA, in what is one of the most significant biological discoveries ever made. An examination of x-ray crystallography work by another researcher allowed the duo to determine that DNA is a double-helical molecule – a helical structure with two DNA strands, each with a carbon-phosphate backbone, and pairs of nucleotides arranged like rungs on a ladder.

    This discovery was important not only for its own sake but also because it suggested two important facts about genetic inheritance:

    • That genetic information was carried by the sequence of nucleotides on the DNA strands
    • That DNA replication could be achieved if the strands were unwound, with each single strand used as the template for a new strand

    Both of these possibilities turned out to be the case.

    Despite the fact that Watson and Crick are most commonly associated with this discovery, there were other people involved. First is Maurice Wilkins, who won the Nobel Prize along with Watson and Crick. Wilkins, a physicist who was born in New Zealand and educated at Cambridge in England, came up with the idea to use x-ray crystallography to study the structure of DNA, and he had already begun work on this when Rosalind Franklin was appointed to work at King’s College.

    Rosalind Franklin, despite the importance of her contribution, was not awarded a Nobel Prize: Nobel regulations prohibit posthumous awards, and Franklin had died in 1958 of cancer, aged 37, before the award was made. Rosalind Franklin’s contribution was a vital one: it was her x-ray crystallography work which Watson and Crick used to determine the double-helical structure of DNA.