If a DNA molecule had a total of 1000 nucleotides and 200 of these are adenines, then the total number of pyrimidines is 500. Adenines (A) are purine bases.
DNA is a double helix molecule composed of two long chains of nucleotides that are held together by hydrogen bonds.
In DNA, there are four types of nucleotides, each containing one different nitrogenous base: Adenine (A), Guanine (G), Cytosine (C) and Thymine (T).
Adenine (A) and guanine (G) are purines, whereas cytosine (C), thymine (T), are pyrimidines.
According to the base pair rules, Adenine always pairs with Thymine, whereas Guanine pairs with Cytosine.
In this case, the number of A + T is equal to 400 (200 + 200) and the number of G + C is 600 (300 + 300), thereby the number of pyrimidines or C + T is equal to 500 (200 + 300).
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