DNA base pairing: why adenine pairs with thymine
In standard DNA, adenine pairs with thymine and guanine pairs with cytosine; complementary pairs help preserve genetic information during replication.
DNA consists of two strands whose bases pair specifically: A with T and G with C. The pairing rules arise from molecular structure and hydrogen bonding, and the two strands run in opposite directions.
What the evidence says
RNA usually uses uracil in place of thymine. The familiar DNA pairing A–T should not be copied unchanged into every question about RNA.
Exam note
For exam revision, retain the key definition and consult the linked primary source when a current rule or technical detail matters.
Editorial note
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Frequently asked questions
Which bases pair in standard DNA?
Adenine pairs with thymine, and guanine pairs with cytosine.