A reverse complement is formed by two operations: first the DNA sequence is reversed, then each base is replaced with its Watson-Crick complement. Adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).
The result represents the opposite strand of the original double-stranded DNA molecule, written in the conventional 5′ → 3′ direction.
G A T T A C AReversed 3′ → 5′A C A T T A GReverse complement 5′ → 3′T G T A A T CSequence easter egg: Gattaca
A complement replaces every base with its Watson-Crick partner without changing the input order. For a 5′ → 3′ input sequence, the aligned complement is the opposite strand written 3′ → 5′.
G A T T A C AComplement 3′ → 5′C T A A T G TA reverse reads the original sequence backwards, from the last base to the first, without changing any bases. This is less often biologically meaningful by itself, but it can help when checking sequence orientation or palindromes.
G A T T A C AReversed 3′ → 5′A C A T T A G