DNA → RNA Transcription
Transcribe a DNA sequence into RNA.
Length: 0 bases
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What it does
This tool converts a DNA coding strand written 5' to 3' into the corresponding RNA sequence by replacing every thymine with uracil, preserving length, order and directionality. Characters that are not standard bases are passed through unchanged, so ambiguity codes and formatting survive the conversion. It is used in teaching to make the DNA-to-RNA relationship concrete, and at the bench to write out an mRNA, guide RNA or probe sequence before ordering or folding it.
How it works
In the cell, RNA polymerase binds the template strand and reads it 3' to 5' while synthesizing RNA 5' to 3', inserting the complementary ribonucleotide at each step. The consequence is that the RNA product is identical in sequence to the coding strand except that uracil takes the place of thymine, so the transformation reduces to the single substitution rule T to U (and t to u). Nothing else changes: the length is the same, no bases are reversed or complemented, and the 5' to 3' orientation is preserved. This shortcut only holds for the coding strand; if you paste the template strand you must take its reverse complement first, otherwise the result will be the antisense RNA rather than the message.
Worked example
The coding strand 5'-ATGGCTTAA-3' becomes the RNA 5'-AUGGCUUAA-3'. Three thymines at positions 2, 6 and 7 are replaced by uracil, the length stays at 9 nucleotides, and the reading frame is untouched, so AUG is still the start codon and UAA is still the stop codon. Read as codons, AUG GCU UAA encodes methionine then alanine and then terminates.
When to use it
When you have a coding sequence and need the mRNA to hand to a codon table or a translation exercise, converting T to U gives the sequence in the form the genetic code is written in. When ordering an in vitro transcribed probe, a guide RNA or an antisense oligonucleotide, writing out the RNA sequence explicitly helps you check the 5' end and any added leader before it is synthesized. When preparing input for RNA secondary structure prediction, most folding tools expect U rather than T, so the converted sequence can be pasted in directly.
FAQ
- What is the difference between the coding strand and the template strand?
- The template strand is the one RNA polymerase actually reads, so the RNA is complementary to it. The coding strand is the other strand, which has the same sequence as the RNA apart from T versus U, which is why it is the strand normally written in databases and papers. This tool assumes you are giving it the coding strand.
- Does transcription change the length of the sequence?
- No. The substitution of uracil for thymine is one-for-one, so the RNA has exactly as many nucleotides as the DNA you entered and every position keeps its index. Real transcription in a cell can of course add a 5' cap and a poly-A tail and remove introns, but none of that is part of this base-level conversion.
- How do I get RNA from the template strand?
- First convert the template strand to its reverse complement to obtain the coding strand, then replace T with U. If you skip the reverse complement step you will produce the antisense RNA, which will not translate into the intended protein and will read as nonsense against a codon table.
- Why does RNA use uracil instead of thymine?
- Thymine is simply 5-methyluracil, so the two bases pair with adenine in the same way and the methyl group is not needed for base pairing. The usual explanation is that DNA keeps the methylated form so that uracil appearing in DNA can be recognized as damage from cytosine deamination and repaired, a safeguard that a short-lived RNA molecule does not require.