DNA to protein sim
Make an mRNA copy of a short gene, drag a ribosome along it to read the triplets into a chain of amino acids, then change one base of the gene and read it again to see the protein stay the same, change one amino acid or stop early.
How a gene codes for a protein: a gene as a section of DNA coding for one polypeptide, the triplet code (three bases code for one amino acid), the mRNA copy made in the nucleus and read by a ribosome in the cytoplasm from a start to a stop triplet, and how changing one base can leave the protein the same, swap one amino acid or stop the chain early · covers the O-Level, IGCSE, GCSE topic
What the sim shows
DNA to protein: teaching models of a gene, its mRNA copy, a ribosome and a chain of amino acids. A gene is a section of DNA whose order of bases codes for the order of amino acids in one polypeptide (a protein): each triplet of three bases codes for one amino acid. The gene stays in the nucleus; an mRNA copy of it is made by pairing with one strand (U in mRNA pairs with A), and a ribosome in the cytoplasm reads the copy triplet by triplet, from the start triplet AUG to a stop triplet, joining the amino acids into a chain. Changing one base changes one triplet: the protein may stay the same (61 of the 64 triplets code for 20 amino acids (3 are stop triplets), so most amino acids have several), have one amino acid changed, or stop early at a new stop triplet. Simplified on purpose: a short made-up gene of 21 bases (7 triplets) stands for a real gene of hundreds or thousands of bases; the start and stop triplets are locked; only the 15 bases between them can be changed, and only one at a time, by swapping one base for another (no bases added or taken out); the copying of the gene into mRNA happens in one step, and the mRNA is drawn as a straight strip; the ribosome is drawn as two plain shapes; the molecules that bring each amino acid to it are not drawn; the amino acids are drawn as beads with their three-letter names; a real chain folds up into a shape as it is made; a changed base pair is shown at once on both strands; the bench pieces are teaching models, not real objects at any one scale.
- Glow: the model in use; lit part: the model ribosome
- Close-up: the gene, its mRNA copy and the chain, in triplets
- Dashed outline: a base you can drop a new base on
Use it in your lessons
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