Paste a DNA sequence and instantly get the transcribed messenger RNA (mRNA) strand. Choose whether you are entering the coding (sense) strand or the template (antisense) strand, and see base counts, GC content, and codon count alongside the transcript.
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Reviewed July 2026
Standard molecular biology transcription rules (Watson-Crick base pairing, T to U substitution).
1. DNA Sequence
2. About This Converter
If you enter the coding strand, the mRNA is identical to your input with every T replaced by U.
If you enter the template strand, the mRNA is built by taking the complementary base for each letter (A↔U, T→A, C↔G), because RNA polymerase reads the template strand and synthesises a complementary mRNA strand.
Only the letters A, T, C and G are valid DNA bases. Spaces, numbers and line breaks are ignored automatically.
mRNA transcript (5' to 3')-
Sequence Summary
Length
-
Bases (nucleotides)
GC Content
-
% of G and C bases
Codons
-
Complete 3-base groups
Start Codon
-
First AUG found
Base Counts (Input DNA)
Adenine (A)-
Thymine (T)-
Cytosine (C)-
Guanine (G)-
Transcription Details
Strand entered-
Method used-
Uracil (U) in mRNA-
mRNA length-
Result:Enter a DNA sequence above to see the mRNA transcript.
How DNA to mRNA Conversion Works
Transcription is the process by which a cell copies a segment of DNA into messenger RNA (mRNA), which then carries the genetic instructions to the ribosome for protein synthesis. RNA polymerase binds to the DNA template (antisense) strand and reads it in the 3' to 5' direction, building a new mRNA strand in the 5' to 3' direction. The resulting mRNA is complementary to the template strand and, aside from one key difference, identical to the coding (sense) strand.
The T to U Substitution
DNA and RNA use four bases each, and three are shared: adenine (A), cytosine (C), and guanine (G). The fourth base differs: DNA uses thymine (T), while RNA uses uracil (U) in its place. Both thymine and uracil pair with adenine, so the substitution does not change the base-pairing logic, only the chemical structure of that one base.
DNA Coding Strand Base
mRNA Base
A
A
T
U
C
C
G
G
Coding Strand vs Template Strand
Double-stranded DNA has two strands running in opposite directions. The coding strand (sense strand) has the same base sequence as the mRNA transcript, apart from T instead of U, which makes it easy to read off the mRNA sequence directly. The template strand (antisense strand) is the one RNA polymerase physically reads, and it is the complementary strand to both the coding strand and the resulting mRNA. To get mRNA from a template strand, first find the complementary base for every position (A pairs with U, T pairs with A, C pairs with G, and G pairs with C), rather than a straight T to U swap.
Reading the Output
This tool also reports the GC content (the percentage of guanine and cytosine bases), which is a useful indicator of DNA stability since G-C pairs form three hydrogen bonds compared to two for A-T pairs. It counts complete codons (groups of three bases) in the mRNA, since codons are the units the ribosome reads during translation, and it flags the first AUG codon found, which is the standard start codon that initiates translation in most genes.
Frequently Asked Uses
Checking transcription homework or lab report answers
Converting a known coding-strand sequence to its mRNA form for further analysis
Understanding the relationship between a gene's template strand and its mRNA transcript
Quickly checking GC content and codon counts for a short DNA fragment
Sources: Standard Watson-Crick base pairing rules and transcription mechanics as taught in molecular biology (Alberts et al., Molecular Biology of the Cell; NCBI Bookshelf, Molecular Biology of the Gene).
This tool performs a straightforward base substitution or complementation and does not account for RNA splicing, introns, post-transcriptional editing, or promoter and terminator sequences. It is intended as a study and reference aid, not a substitute for laboratory sequencing or full gene annotation.
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