Chargaffszabályok

Chargaffszabályok (Chargaff's rules) is a fundamental principle in molecular biology concerning the base composition of DNA. These rules were formulated by Austrian biochemist Erwin Chargaff in the late 1940s. The primary observations are that in any sample of double-stranded DNA, the amount of adenine (A) is approximately equal to the amount of thymine (T), and the amount of guanine (G) is approximately equal to the amount of cytosine (C). Expressed mathematically, this means A ≈ T and G ≈ C. Furthermore, the sum of purines (A + G) is approximately equal to the sum of pyrimidines (T + C). These rules hold true across a wide variety of species, indicating a conserved feature of DNA structure. Chargaff's findings were crucial for later scientists, particularly James Watson and Francis Crick, in determining the double helix structure of DNA, as the base pairing rules directly explain these observed ratios. The complementary base pairing, where A always pairs with T and G always pairs with C, is the underlying molecular mechanism responsible for Chargaff's observations. Deviations from these rules can occur in single-stranded DNA or in RNA molecules.