DNA Sequence Toolkit
Reverse complement, GC content, and CpG finder — without sending your sequences to a server.
Sequence analysis
Ready when you are
Load the example or paste a DNA sequence to see reverse complements, GC content and CpG positions.
Some bases are ambiguous. GC content is therefore shown as the minimum–maximum possible percentage, not a misleading exact value. Only definite CG pairs count as CpG.
Reverse complement · 5′ → 3′
Show original and complement
CpG positions
Positions are 1-based, measured on the input strand. Context includes up to nine flanking bases on each side.
No confirmed CG dinucleotides in this sequence.
| Position | Sequence context |
|---|
All sequences
| Sequence | Length (bp) | GC content | Ambiguous | CpG sites |
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What the results mean
Reverse complement: bases are reversed and paired by A↔T and C↔G. IUPAC uncertainty is also complemented correctly (for example, R↔Y, K↔M, B↔V).
GC content: for A, C, G, T DNA it is (G + C) / sequence length × 100. For ambiguous IUPAC symbols, the tool reports a valid minimum–maximum GC percentage. It does not arbitrarily assume ambiguous bases are evenly distributed.
CpG sites: the tool finds literal CG pairs in the supplied 5′→3′ sequence and reports the C position starting at 1. Ambiguous pairs are not counted as confirmed CpG sites. These are sequence positions, not measurements of DNA methylation.
Important: no genome alignment, gene annotation, restriction-enzyme analysis, oligo specificity checking or primer design is performed. Always verify sequence origin and orientation for laboratory work.
Need more than a sequence calculation?
For methylation assays, PCR study design and molecular diagnostic development, explore independent scientific consulting.
Cite this toolCopy · BibTeX · RIS
ResearchTools can be cited using the project DOI: 10.5281/zenodo.23302683. This toolkit is a new web addition and is not included in the Zenodo v1.6.9 archive.
Identify the exact web version and operations used. The Zenodo 1.6.9 version DOI refers to the previous release and should not be presented as covering this new tool.