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Complementary base pairing

Complementary base pair describes the way in which nitrogenous bases from opposite DNA strands interact.

Not all bases can interact with each other. Their different shapes and sizes mean that only certain pairs are allowed. This is called the base pairing rule:

  • Adenine (A) pairs with thymine (T)
  • Cytosine (C) pairs with guanine (G)

Each base only pairs with one other base, so if you know the sequence of one strand of a DNA molecule you can work out the sequence of its complementary strand!

The complementary sequence of A-G-A-C is T-C-T-G

Complementary base pairings.
Complementary base pairings.