Erwin Chargaff

Erwin Chargaff (August 11, 1905 – June 20, 2002) was an Austrian biochemist. Through careful experimentation, Chargaff discovered two rules that helped lead to the discovery of the double helical structure of DNA.

Chargaff's rules

Erwin Chargaff proposed two main rules in his lifetime which were appropiately named Chargaff's rules. The first and best known achievement was to show that in natural DNA the number of guanine units equals the number of cytosine units and the number of adenine units equals the number of thymine units. In human DNA, for example, the four bases are present in these percentages: A=30.9% and T=29.4%; G=19.9% and C=19.8%. This strongly hinted towards the base pair makeup of the DNA, although Chargaff was not able to make this connection himself. For this research, Chargaff is credited with disproving the tetranucleotide hypothesis (Phoebus Levene's widely accepted hypothesis that DNA was composed of a large number of repeats of GACT). Most workers had previously assumed that deviations from equimolar base ratios (G = A = C = T) were due to experimental error, but Chargaff documented that the variation was real, with typically being slightly less abundant. He was able to do this with the newly developed paper chromotography and ultraviolet spectrophotometer. Chargaff met Francis Crick and James D. Watson at Cambridge in 1952, and, despite not getting on well with them personally, explained his findings to them. Chargaff's research would later help Watson and Crick to deduce the double helical structure of DNA.

Related Topics:
Chargaff's rules - DNA - Guanine - Cytosine - Adenine - Thymine - Base pair - Tetranucleotide hypothesis - Phoebus Levene - Paper chromotography - Ultraviolet - Spectrophotometer - Francis Crick - James D. Watson - Cambridge - 1952 - Double helical

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The second of Chargaff's rules is that the composition of DNA varies from one species to another, in particular in the relative amounts of A, G, T, and C bases. Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a more credible candidate for the genetic material than protein.

Related Topics:
Genetic material - Protein

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Besides making these important steps toward the structure of DNA, Chargaff's lab also conducted research on the metabolism of amino acids and inositol, blood coagulation, lipids and lipoproteins, and the biosynthesis of phosphotransferases.

Related Topics:
Metabolism - Amino acids - Inositol - Coagulation - Lipid - Lipoprotein - Biosynthesis - Phosphotransferase

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