Codon Protein Builder

About this simulation

Codon Protein Builder lets students type an mRNA sequence by clicking the bases A, U, G and C or pressing the keys. Each time three bases are entered, the ribosome reads the codon, a tRNA with the matching anticodon delivers an amino acid, and the protein chain grows. Translation begins at AUG for methionine and stops at UAA, UAG or UGA. Readouts show the last codon, the protein so far, its length and approximate mass. A random gene button, an Undo base button and a fast ribosome toggle help. It teaches translation and the genetic code.

What students can explore

Click A, U and G to start with the start codon AUG and see the first amino acid added.
Type a second codon and watch the tRNA bring its amino acid to the ribosome.
Enter UAA, UAG or UGA and watch the ribosome stop and release the protein.
Press Type a random gene to see a full translation and then Undo base to step back.
Switch on Fast ribosome and compare the length and mass readout for different genes.

Learning objectives

1Describe how mRNA codons specify amino acids during translation.
2Identify the start codon AUG and the three stop codons.
3Translate a short mRNA sequence into an amino acid chain.
4Explain the role of tRNA and the ribosome in building proteins.

Questions teachers ask

Is it free?

Yes, completely free with no login. Any modern browser will run it, so it works on school tablets, whiteboards and personal phones.

How many codons are there?

There are 64 possible codons, since three bases each have four choices. They code for 20 amino acids plus a stop signal, so several codons can code for the same amino acid.

What starts and stops translation?

Translation starts at AUG, which codes for methionine. It ends at a stop codon, UAA, UAG or UGA, which do not code for any amino acid.

How do I enter a sequence?

Click the base buttons A, U, G and C or press those keys. The Next codon readout shows what you have typed so far, and Undo base removes the last base.

Embed this simulation

Drop it into your LMS, blog, or class site — free.

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