Calculator
Enter a DNA sequence using only A, C, G and T. This learning tool returns the complementary strand in antiparallel orientation and a reverse complement in 5′→3′ orientation.
Method and input format
DNA Sequence Helper
Formula: A pairs with T; C pairs with G; GC% = (G + C) / total bases x 100
Assumption: The entered sequence is DNA and contains only the standard bases A, C, G and T.
Worked example
DNA Sequence Helper
For 5'-ATGC-3', the complementary strand is 3'-TACG-5' and the reverse complement is 5'-GCAT-3'.
Reading DNA sequence results
| Sequence (5'→3') | Reverse complement | GC content |
|---|---|---|
| ATGC | GCAT | 50% |
| GGCCTA | TAGGCC | 66.7% |
| ATATAT | ATATAT | 0% |
| GAATTC (EcoRI site) | GAATTC | 33.3% |
A sequence that equals its own reverse complement, such as GAATTC, is palindromic; many restriction enzymes recognise sites like this. GC content matters because G–C pairs are held by three hydrogen bonds and A–T pairs by two, so GC-rich stretches generally melt at higher temperatures. PCR primers are commonly designed with a GC content of roughly 40-60%.