World of Scientific Discovery on Rosalind Elsie Franklin
Deoxyribonucleic acid (DNA) carries the genetic instructions for life. Johann Miescher (1844-1895), a Swiss physician, discovered DNA in 1869 while studying the composition of white blood cells. Nearly one hundred years passed before James Watson and Francis Crick were credited with the discovery of the actual structure of DNA. Many scientists contributed to this discovery--not the least of whom was Rosalind Franklin.
Franklin was born in London on July 25, 1920. She graduated from Cambridge University in 1941. She conducted experiments using chromatographic techniques and later worked at a laboratory in Paris, France, where she learned to develop x-ray diffraction photographs. In 1951, she used these skills to carefully construct x-ray diffraction photos of DNA under varying degrees of humidity. Together with her colleague, Maurice Wilkins, she noted that the pictures showed the molecule to be a helical shape. She remained skeptical, however, that DNA would actually take up a helical form under all conditions.
James Watson was later shown the photographs by Wilkins, apparently without the consent of Franklin. The photographs strongly supported Watson and Crick's hypothesis of a double-stranded helical DNA molecule. In 1953, this model was publicly presented by Watson and Crick. The double-helix, or twisted ladder shape, is made of sugar-phosphate units of nucleotides. These nucleotides form the sides of the ladder. The rungs are formed by four nitrogenous bases, including adenine and guanine (the purines) and thymine and cytosine (the pyrimidines). Each rung consists of two bases. Knowledge of the distances between the atoms, as determined by x-ray diffraction, was crucial in establishing the structure of the DNA model.
Francis Crick admitted in a Nature article that "Rosalind Franklin was only two steps away from the solution. She needed to realize that the two chains must run in opposite directions and that the bases, in their correct tautomeric forms, were paired together." Although Franklin was on the verge of solving the mystery of DNA structure, it was during this time that she chose to leave King's College and DNA to study the tobacco mosaic virus. She was instrumental in showing how the nucleic acid molecules of the virus existed in a helical array of repeated protein units.
Perhaps Rosalind Franklin's most amazing accomplishment is the relatively short period of time in which she contributed such valuable scientific information. She died in London of cancer on April 16, 1958, at the early age of 37. This was four years before Watson, Crick, and Wilkins received the Nobel Prize in physiology or medicine. Many people believe that Franklin's work has been underestimated due to her untimely death and the female prejudices of the English scientific establishment in the 1950s.
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