James Watson & Francis Crick By John Matthews & Meghen Young

Facts James Watson was born on April 6, 1928 in Chicago. He was an American biologist. Francis Crick was born on June 8, He was a British physicist. They were both trying to understand the structure of DNA.

Main Contribution to DNA Watson and Crick discovered the molecular structure of DNA. They proposed that the DNA molecule consisted of two spirally wound, helical chains. They demonstrated how genetic information passed through DNA in genes. In 1968, Watson published The Double Helix.

Rosalind Franklin Franklin used a technique called X-ray diffraction to get information about the structure of the DNA molecule. First, she purified a large amount of DNA, the stretched the DNA fibers in a thin glass tube so that most of the strands were parallel. Next, she aimed a powerful X-ray beam at the concentrated DNA samples and recorded the scattering pattern of the X-rays on film. Franklin’s patterns does not reveal the structure of DNA, X-shaped pattern shows that the strands in DNA are twisted around like the coils of a spring, a shape known as a helix. Her X-ray pattern enabled Watson and Crick to build a model that explained the specific structure and properties of DNA

Erwin Charagaff Charagaff discovered that the percentages of adenine and thymine bases are almost equal in any sample of DNA. The same thing is true for the other to nucleotides, guanine and cytosine. This observation became known as “Charagaff’s rule” Watson and Crick found that if you paired adenine with thymine and guanine with cytosine it would look uniform. This was correct in accordance to Charagaff’s Rule.

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