Nitrogenous bases are heterocyclic, planar, and relatively water-insoluble aromatic molecules.DNA consist of two types of nitrogenous bases-Purines and Pyrimidines.
Purines-The two common purine bases found in DNA are Guanine and Adenine.
Pyrimidine-The two common pyrimidine bases found in DNA are Thymine and Cytosine.
- According to the base-pairing rule in DNA- Adenine (purine) pairs with Thymine (Pyrimidine) and Guanine (purine) pairs with Cytosine.
- Adenine pairs with Thymine with two hydrogen bonds and Guanine pairs with Cytosine with three hydrogen bonds.
So, the correct answer is option A.) Adenine-Thymine; Cytosine-Guanine
Other option
B.) Adenine-Cytosine; Guanine-Thymine is incorrect because adenine pairs with thymine and guanine pairs with cytosine.
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