Long before Crick and Watson had worked out the structure of DNA, Phoebus Levene (1869-1940) had discovered that the cell nucleus contains two types of nucleic acids - DNA and RNA. He also found that DNA contained the four bases, deoxyribose, and a phosphate group.
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Who was Phoebus Levene?
Phoebus Levene was a Russian-American biochemist. He emigrated to America after gaining his MD from St. Petersburg in 1891. He developed an interest in chemistry and enrolled in classes a Columbia University, New York. He joined the Rockefeller Institute for Medical research in 1905 and remained there for the rest of his career.
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Nucleic Acid Structure
Prior to Levene's research, some fundamental facts about nucleic acids were known.
Studies had already alighted on the fact that there are two nucleic acids. One had been discovered in the thymus of animals and Albrecht Kossel had shown that it contained adenine, guanine, cytosine, and thymine. The other type of nucleic acid was found in yeast and differed by the presence of uracil instead of thymine. Carbohydrate and phosphorous were also present. But little was known about nucleic acid structure or its functions.
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Nucleic Acid Research of Phoebus Levene
Levene discovered that the carbohydrate present in yeast nucleic acid was in fact ribose. But it wasn't until 20 years later that he identified the carbohydrate in thymus nucleic acid. He discovered that it was also a sugar, and that it differed from ribose because it lacked one oxygen atom - so he called it deoxyribose. And that wasn't all. He also worked on nucleic acid structure and demonstrated that units were formed by the various components linking together - phosphate-sugar-base. He coined the term nucleotide.
A nucleotide is any one of the bases, plus a sugar and a phosphate group.
It was Levene's contention that nucleotides in a DNA molecule are always linked in the same order - i.e. A-C-T-G-A-C-T-G-A-C-T-G. As scientists now know this is far too simplistic and the arrangement of nucleotides is highly variable.
Levene believed in the scientific consensus at the time that DNA was far too simple a molecule to be the basis of biological individuality. The more complex protein structure was favoured. There are some who consider that Levene contributed to sending a generation of scientists down a blind alley to look for the molecular basis of heredity amongst amino acids.
What is without doubt though, is that this brilliant chemist's groundbreaking research was a crucial part in the discovery of DNA structure.
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Pray, L. (2008) Discovery of DNA structure and function: Watson and Crick. Nature Education 1(1)