Sequence
Reverse complement
Turn a DNA sequence into its complement, reverse, reverse complement or RNA, with FASTA input and full IUPAC ambiguity support. Your sequence is never uploaded.
Input sequence
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Formula
5'-ATGGCC-3' → 5'-GGCCAT-3'
- complement
- each base swapped for its partner: A↔T and G↔C
- reverse
- the order of bases flipped, the bases themselves unchanged
- reverse complement
- both at once — the opposite strand read 5′ to 3′
Worked example
Designing a reverse primer from the 3′ end of a target region
- target region: 5'-ATGGCCTAGGAATTCACG-3'
- Take twenty to twenty-five bases from the 3′ end of the region.
- Take the reverse complement of that stretch.
- The result is your reverse primer and must be written 5′ to 3′.
Answer 5'-CGTGAATTCCTAGGCCAT-3'
Common mistakes
- Taking the complement instead of the reverse complement when designing a reverse primer. The bases are right but the direction is wrong and the primer will not work.
- Forgetting that sequences are always written 5′ to 3′. Writing the opposite strand 3′ to 5′ is a common source of confusion when ordering oligos.
- Ignoring ambiguity codes. N and the other IUPAC symbols have complements too, and this tool converts them correctly.
Frequently asked
Why is reverse complement different from reverse?
Reverse only flips the letters and produces a meaningless sequence. Reverse complement gives the real opposite strand — the one sitting across from yours in double-stranded DNA.
Is FASTA input supported?
Yes. A header line beginning with a greater-than sign is read, kept, and reappears in the FASTA download.