DNA Reverse Complement
Compute the reverse complement of a DNA sequence.
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What it does
A reverse complement is the sequence you get by reversing a DNA or RNA strand and swapping each base for its partner (A↔T, C↔G; RNA uses U instead of T). It is the sequence of the opposite strand written in the standard 5'→3' direction — the form you need for primers, probes, and cloning. Double-stranded DNA stores two antiparallel strands, and most databases (GenBank, oligo order sheets) list only one. Being able to flip to the other strand on demand is a routine part of sequence work.
How it works
Two steps: (1) Complement — replace every base with its partner (A↔T, C↔G; A↔U for RNA). (2) Reverse — read the result backwards. For RNA, uracil (U) replaces thymine (T). Because polymerases extend 5'→3', primers annealing to the reverse strand must be ordered as the reverse complement of the reference sequence, not as the plain complement. Input accepts mixed case and whitespace, and preserves IUPAC ambiguity codes where a unique partner exists.
Worked example
Sequence 5'-ATGC-3'. Complement: TACG. Reverse: GCAT. Reverse complement: 5'-GCAT-3'. The plain complement (no reversal) is 5'-TACG-3'. Try a short oligo like 5'-ACGTTTGA-3': its reverse complement is 5'-TCAAACGT-3', which you can verify base by base. Palindromic restriction sites such as 5'-GAATTC-3' (EcoRI) map onto themselves — easy to confirm with this tool.
When to use it
Use it to design PCR primers and sequencing primers, annotate the opposite strand, plan restriction or cloning steps, and verify an antisense or siRNA sequence. It is also the standard way to check whether two sequences are the same strand written in opposite directions, and to prepare antisense probe sequences.
FAQ
- What is a DNA reverse complement?
- The reverse complement of a DNA strand is obtained by reversing the sequence and replacing each base with its complement: A↔T and C↔G. It represents the complementary strand read in the 5'→3' direction. For example, the reverse complement of 5'-ATGC-3' is 5'-GCAT-3'.
- How do I find the reverse complement of a DNA sequence?
- Paste your DNA sequence into the input field above. The reverse complement is computed instantly as you type. Only A, C, G, T (case-insensitive) are complemented; IUPAC ambiguity codes (R, Y, N, etc.) are preserved as-is.
- What is the difference between complement and reverse complement?
- The complement swaps each base for its partner but keeps the original 5'→3' order (ATGC → TACG). The reverse complement also reverses the order (ATGC → GCAT). Primers and the opposite strand use the reverse complement.
- Can I reverse complement RNA sequences?
- Yes. RNA uses uracil (U) instead of thymine (T), so A pairs with U. Enter your RNA sequence and the tool returns the reverse complement using A↔U and C↔G.