AP BIOLOGY

Detailed explanation-1: -Chargaff rule: The rule that in DNA there is always equality in quantity between the bases A and T and between the bases G and C. (A is adenine, T is thymine, G is guanine, and C is cytosine.) Named for the great Austrian-American biochemist Erwin Chargaff (1905-2002) at Columbia University who discovered this rule.

Detailed explanation-2: -Chargaff’s rules state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine. Further a 1:1 stoichiometric ratio of purine and pyrimidine bases (i.e., A+G=T+C ) should exist.

Detailed explanation-3: -Erwin Chargaff found that in DNA, the ratios of adenine (A) to thymine (T) and guanine (G) to cytosine (C) are equal. This parity is obvious in the final DNA structure.

Detailed explanation-4: -He became interested in DNA in 1944 after Oswald Avery identified the molecule as the basis of heredity. In 1950, he discovered that the amounts of adenine and thymine in DNA were roughly the same, as were the amounts of cytosine and guanine. This later became known as the first of Chargaff’s rules.

Detailed explanation-5: -In the 1950s, a biochemist named Erwin Chargaff discovered that the amounts of the nitrogenous bases (A, T, C, and G) were not found in equal quantities. However, the amount of A always equalled the amount of T, and the amount of C always equalled the amount of G.