Complementary base pairing — Science definition
The rule that adenine always pairs with thymine (A-T) and cytosine always pairs with guanine (C-G).
Where it is taught
- DNA Structure & Replication — DNA, Inheritance & Gene Expression, Life Science: Biology, Grade 10
In use
Adenine always bonds with thymine (A-T), and cytosine always bonds with guanine (C-G) — a principle called complementary base pairing.
DNA Structure & Replication
Questions using complementary base pairing
Problem 1
Why does complementary base pairing make DNA easy to copy accurately?
- Each strand acts as a template that determines exactly which bases must be added to build its partner
- The bases pair together completely at random
- Both strands are identical, so one can be thrown away
- DNA does not need to be copied before a cell divides
Answer and explanation
Each strand acts as a template that determines exactly which bases must be added to build its partner
Because A only pairs with T and C only with G, one strand's sequence dictates its partner's, so each old strand is a perfect template for building a new one.