DNA to RNA converter

Transcribe DNA to mRNA from either strand, or turn RNA back into DNA. Computed as you type, nothing leaves the browser.

mRNA

How do you convert DNA to RNA?

It depends on which DNA strand you have. During transcription RNA polymerase reads thetemplate strand 3′→5′ and builds an mRNA that is complementary to it. That mRNA therefore has the same sequence as the other strand, the coding strand, with uracil in place of thymine.

coding strand → mRNA: replace T with U
template strand → mRNA: reverse complement, then replace T with U

Sequences in GenBank, Ensembl and most papers are coding strands, so the first tab is the one you usually want. Use the second tab when you have been given the antisense strand, for example the minus strand of a genome region or a textbook transcription exercise.

Worked example: coding strand, template strand and mRNA

StrandDirectionSequence
Coding (sense) DNA5′→3′ATGGCCTTAGAATGA
Template (antisense) DNA5′→3′TCATTCTAAGGCCAT
mRNA5′→3′AUGGCCUUAGAAUGA

Paste ATGGCCTTAGAATGA with the Coding strand → mRNA tab selected, or pasteTCATTCTAAGGCCAT with Template strand → mRNA: both giveAUGGCCUUAGAAUGA, 15 nt. The mRNA reads AUG GCC UUA GAA UGA, which translates to Met-Ala-Leu-Glu-stop.

The template strand is entered 5′→3′ like every other sequence. If your exercise writes the template 3′→5′ (for example 3′-TACCGGAATCTTACT-5′), only the bases need complementing and the order stays; the reverse complement calculator has a Complement tab for that, after which T→U gives the mRNA.

How to transcribe a DNA sequence with this tool

  1. Paste the sequence. Plain text, numbered GenBank-style text and single or multi-record FASTA all work; whitespace and digits are ignored.
  2. Pick the tab that matches your input strand. The result updates as you type and shows the number of records and the length in nucleotides.
  3. Press Copy. The copied text is wrapped at 60 characters per line, with FASTA headers kept on their records.

Upper and lower case are preserved, so soft-masked repeats or lower-case introns stay marked. IUPAC ambiguity codes are kept as they are on the coding-strand and RNA tabs and complemented on the template tab (R↔Y, K↔M, B↔V, D↔H; S, W and N are unchanged).

How do you convert RNA back to DNA?

Replace every U with T. This is what the RNA → DNA tab does, and the result is the coding-strand DNA of the transcript, the sense strand of its cDNA. ForAUGGCCUUAGAAUGA the output is ATGGCCTTAGAATGA. For the first-strand cDNA that reverse transcriptase actually synthesises, take thereverse complement of that result.

Why does RNA use uracil instead of thymine?

Thymine is 5-methyluracil; both bases pair with adenine through the same two hydrogen bonds. Cytosine spontaneously deaminates to uracil, and in DNA the methyl group on thymine lets repair enzymes tell a legitimate T from a damaged C. RNA is made in large amounts and degraded quickly, so the cell skips the methylation step and uses uracil.

What comes after transcription?

The mRNA is read in codons of three bases starting at AUG. Translate the result with theprotein translation tool, look up single codons in thecodon table, or search both strands for open reading frames with the ORF finder. Note that this tool performs the base conversion only: it does not remove introns, add a 5′ cap or a poly(A) tail.

Frequently asked questions

How do you convert DNA to RNA?

If the DNA is the coding (sense) strand, replace every T with U. The coding strand ATGGCCTTAGAATGA becomes the mRNA AUGGCCUUAGAAUGA. If the DNA is the template (antisense) strand, take its reverse complement and write it with U instead of T.

What is the difference between the coding strand and the template strand?

The template strand is the one RNA polymerase reads. The mRNA is complementary to it and therefore has the same sequence as the other strand, the coding strand, with U in place of T. Gene sequences in databases such as GenBank are given as the coding strand.

Why does RNA have U instead of T?

Uracil and thymine pair with adenine in the same way. Thymine is uracil with an extra methyl group, which lets DNA repair enzymes recognise uracil produced by cytosine deamination as damage. RNA is short-lived, so it uses the cheaper base.

Can I convert RNA back to DNA?

Yes. Choose the RNA to DNA tab and every U is replaced with T, which gives the coding-strand DNA (the cDNA sense strand) of the RNA.

Are FASTA files and IUPAC ambiguity codes supported?

Yes. Multi-record FASTA keeps each header with its record, upper and lower case are preserved, and ambiguity codes such as R, Y and N are kept or complemented correctly.