Reverse Complement Tool
Get the reverse complement, complement or reverse of a DNA or RNA sequence. IUPAC ambiguity codes are handled and RNA input returns RNA.
Formula
- the direction in which a strand is written and read
How it works
The two strands of a duplex run in opposite directions. The strand that pairs with a given sequence is therefore its complement read backwards, which is what is needed when designing a reverse primer or reading the opposite strand.
IUPAC ambiguity codes are complemented to their partners (R ↔ Y, K ↔ M, B ↔ V, D ↔ H; S, W and N are unchanged). A sequence containing U and no T is treated as RNA.
Worked example
Find the reverse complement of 5′-ATGC-3′.
- Complement each base: TACG.
- Reverse the order: GCAT.
The reverse complement is 5′-GCAT-3′.
These are the values the calculator opens with, so you can check its output against this example.
Assumptions
- The input is written 5′ to 3′, the usual convention.
- Standard Watson-Crick pairing.
Common mistakes
- Using the complement where the reverse complement is needed. A reverse primer is the reverse complement of the target strand.
- Forgetting that the output is also written 5′ to 3′.
- Mixing T and U in one sequence, which makes it unclear whether the molecule is DNA or RNA.