DNA, RNA, Chromosomes, and Genes

History of Nucleic Acids

What is Chargaff’s rule?

Chargaff’s rule is based on the data generated by Austro-Hungarian-born American biochemist Erwin Chargaff (1905–2002) in his study of the base composition of DNA from various organisms. By comparing the nitrogen base composition of various organisms, he found that in all double-stranded DNA, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine (A = T, G = C). The “law of complementary base pairing” refers to the pairing of nitrogenous bases in a specific manner: in particular, purines pair with pyrimidines. More specifically, adenine must always pair with thymine, and guanine must always pair with cytosine. The basis of this law came from the data from Chargaff’s studies and is known as Chargaff’s law or rule. (For more about DNA base pairing, see this chapter.)


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