Biologists on Genetics Erwin Chargaff (1905-2001) Relative quantities of the nitrogen bases found in...

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Biologists on Genet ics Erwin Chargaff (1905-2001) Relative quantities of the nitrogen bases found in DNA

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Page 1: Biologists on Genetics Erwin Chargaff (1905-2001) Relative quantities of the nitrogen bases found in DNA.

Biologists on Genetics Erwin Chargaff

(1905-2001)

Relative quantities of the nitrogen bases found in DNA

Page 2: Biologists on Genetics Erwin Chargaff (1905-2001) Relative quantities of the nitrogen bases found in DNA.

Background

Page 3: Biologists on Genetics Erwin Chargaff (1905-2001) Relative quantities of the nitrogen bases found in DNA.

About Erwin Chargaff

Born in Austria on August 11, 1905 Receive a doctorate degree of Chemistry

from the University of Vienna in 1928 1944 - Study of DNA and its four chemical

bases - adenine, cytosine, guanine and thymine

Using chromatography technique Discover amounts of adenine and thymine

were equal, as were the amounts of cytosine and guanine

Page 4: Biologists on Genetics Erwin Chargaff (1905-2001) Relative quantities of the nitrogen bases found in DNA.

The 4 nitrogen bases

Page 5: Biologists on Genetics Erwin Chargaff (1905-2001) Relative quantities of the nitrogen bases found in DNA.

The 4 nitrogen bases - Purines Consist of a six-membered and a five-membered nitrogen-containing ring, fused together

Adenine = 6-amino purine

Guanine = 2-amino-6-oxy purine

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The 4 nitrogen bases - Pyrimidines

Have only a six-membered nitrogen-containing ring

Uracil = 2,4-dioxy pyrimidine

Thymine = 2,4-dioxy-5-methyl pyrimidine

Cytosine = 2-oxy-4-amino pyrimidine

Page 7: Biologists on Genetics Erwin Chargaff (1905-2001) Relative quantities of the nitrogen bases found in DNA.

Chargaff's first parity rule

Stated that purines pair with pyrimidines, specifically A with T and C with G

E.g ACGATGCCGTA

With pairing between complementary bases in the "top" and "bottom" strands 

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Chargaff's second parity rule

% of A approximately equals % of T; % of G approximately equals % of C for single strands of DNA

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Cluster rule

Stated that pyrimidines often occur in runs or clusters, and hence on the complementary strand purines do likewise

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GC rule

Stated that (G+C)% is constant within a species, but often differs between species.