Complementary

In genetics, a double-stranded DNA or RNA strand consists of two complementary strands of base pairs, which are non-covalently connected via two or three hydrogen bonds.

Since there is only one complementary base for any of the bases found in DNA/RNA, one can reconstruct a complementary strand for any single strand. This is essential for DNA replication.

For example, the complementary strand of the DNA sequence

A G T C A T G

is

T C A G T A C