Base-Pair Rule In DNA


Base-Pair Rule In DNA


In DNA, each strand sequence of bases is a complement to another strand’s sequence. So if you know the sequence of one strand of DNA, then you can predict the sequence of other strand.

The DNA is made up of four kinds of nitrogenous bases which are :

Guanine (G) Cytosine (C) Adenine (A) Thymine (T)

Two of the bases are purines, which are adenine and guanine. Pyrimidines bases are thymine and cytosine.

These bases are held together by hydrogen bonds. They are formed by complementary pairs of nitrogen bases — Adenine pair with thymine by two hydrogen bonds. Guanine pair with Cytosine by three hydrogen bonds. This is known as the “Base-Pair Rule”. In a double stranded DNA, because of this base pairing , an adenine always pair with thymine and a guanine always pair with cytosine. This is called complementarity of DNA.


1) What would be complementary strand of DNA given below ?


Complementary strand of DNA is :


Suppose you know that the sequence of bases on one DNA strand is AGCTCAG. Then the sequence of the bases on the complementary strand is TCGAGTC, which stands for thymine, cytosine, guanine, adenine, guanine, thymine, and cytosine….

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