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DNA (deoxyribonucleic acid) is a type of genetic material that transmits genetic information from one cell to the next and from one generation to the next. In a cell, DNA directs, governs, and regulates protein synthesis.

Nucleotides are the four basic building blocks of DNA. Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) are the four nucleotides that makeup DNA. Guanine and Adenine are always paired with Thymine and Cytosine.

In 1950, Erwin Chargaffconducted a chemical investigation on DNA bases. According to him, the percentages of Thymine (T) and Adenine (A) are equal, while the percentages of Cytosine (C) and Guanine (G) are equal.

It can be written as,

A+G=C+T

Thus, varied species have different amounts of A, D, T, and C. In every species, the amount of A = T and the amount of G = C is constant.