Transcription, translation and point mutations
BiologyGeneticsAges 17–18
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Genetics
From a gene's template strand, RNA polymerase builds mRNA one nucleotide at a time by base-pairing (A–U, T–A, G–C, C–G); the ribosome then reads each codon from AUG, and tRNA delivers the matching amino acid according to the standard genetic code until a stop codon is reached. Students step through each stage, click a nucleotide to cause a substitution, insertion or deletion mutation, and compare the polypeptide chain before and after (silent, missense, nonsense, frameshift).
Lesson: Gene expression (transcription, translation); gene mutations
What it shows
In transcription, RNA polymerase reads the template strand 3'→5' and builds mRNA 5'→3' by complementary base pairing, with uracil in place of thymine. In translation, the ribosome reads the mRNA three bases at a time from the AUG start codon, and each tRNA anticodon pairs with a codon to add one amino acid until a stop codon ends the chain. Because the code is read in triplets without gaps, a single substitution may change nothing, one amino acid or create a stop codon, while an insertion or deletion shifts the reading frame for every codon after it.
How to use
Type a sequence into Gene template strand, then use Next step or Auto-run to watch transcription and then translation codon by codon. Click any nucleotide of the template strand to substitute it; click again to try another base. For an insertion or deletion, choose it under Mutation and set the position. Compare the Polypeptide row with the Original (no mutation) row and read the mutation type named below.
Parameters you can change
- Gene template strand (3'→5', A T G C only, 6–60 nucleotides)
- Mutation None, Substitution of one nucleotide pair, Insertion of one nucleotide pair, Deletion of one nucleotide pair
- Mutation position on the template strand (from the 3' end) 1–60
- Nucleotide substituted / inserted A, T, G, C
- Auto-run step by step
Questions to explore
- Which mRNA codon is made from the template triplet TAC, and which amino acid does it code for?
- Why does inserting one nucleotide pair near the start codon usually change the polypeptide more than a substitution does?
- Find a substitution that leaves the polypeptide unchanged. Which property of the genetic code explains this?
