In double stranded DNA Select one a purines and pyrimidines

In double stranded DNA Select one: a. purines and pyrimidines do not pair with each other b. purines pair with purines and pyrimidines with pyrimidines c. purines pair with pyrimidines d. purines pair with either purines or pyrimidines

Solution

Answer: c. purines pair with pyrimidines

Reason:

Chargaff’s rule states that the ratio of purines to pyrimidines is 1: 1 in a double stranded DNA. Adenine binds with thymine and guanine binds with cytosine (complementary base pairing).

The four kinds of nucleotides existing in double helix DNA are adenine (A), thymine (T), guanine (G) and cytosine (C). According to Chargaff’s rule of complementarily adenine is complementary to thymine by bonded with 2 hydrogen bonds whereas guanine is complementary with cytosine by bonding with three hydrogen bonds. Chargaff’s rule states that the ratio of purines to pyrimidines is 1: 1 in a double stranded DNA. Adenine binds with thymine and guanine binds with cytosine (complementary base pairing).