DNA Sequence Analyzer
Paste any DNA sequence to instantly get nucleotide counts, GC content, the complementary strand, mRNA transcript, and codon-by-codon protein translation. No signup, runs entirely in your browser.
Molecular Biology Tips
GC content and stability
High GC content sequences are more stable due to the extra hydrogen bond in G-C pairs. PCR primers are typically designed to have 40-60% GC content to ensure reliable annealing.
Start and stop codons
Green AUG codons mark the translation start (methionine). Red Stop codons (UAA, UAG, UGA) terminate translation. In the tool, the first codon is assumed to be the start of the reading frame.
Reading frames
A sequence has three possible reading frames depending on where you start. The tool reads from position 1. If translation gives nonsense, try removing 1 or 2 leading bases to shift the reading frame.
Sequence direction
Enter your sequence 5′ to 3′ (left to right). The complement is shown 3′ to 5′ as it would appear on the antiparallel strand in a double helix.
Frequently Asked Questions
What format should I enter the DNA sequence in?
Enter the sequence using only the letters A, T, C, and G (case-insensitive). Spaces and non-ATCG characters are ignored. Enter the 5′ to 3′ template strand.
What is GC content and why does it matter?
GC content is the percentage of guanine and cytosine bases in a DNA sequence. G-C base pairs form 3 hydrogen bonds (vs 2 for A-T), making GC-rich regions more thermally stable. GC content above 60% indicates a high-melting-temperature sequence; below 40% indicates low stability.
How is the complementary strand generated?
Each base pairs with its complement: A pairs with T, T pairs with A, C pairs with G, and G pairs with C. The complement shown is the 3′ to 5′ strand (antiparallel to the template). To get the reverse complement (5′ to 3′ sense strand), reverse the output.
How does mRNA transcription work?
During transcription, RNA polymerase reads the DNA template and synthesises mRNA. Each T in the DNA is replaced by U in the mRNA (since RNA uses uracil instead of thymine). The mRNA sequence shown is the 5′ to 3′ message.
How is protein translation performed?
The mRNA is divided into codons (triplets of bases). Each codon maps to one amino acid using the standard genetic code. Translation starts at the first AUG (Met) codon and ends at a stop codon (UAA, UAG, or UGA). The tool translates from the beginning of the sequence.
Is my sequence stored?
No. All analysis runs locally in your browser. Your DNA sequence is never sent to any server.