Mutation sim
Swap, add or take out one base of the real start of the beta-globin gene and watch the amino acids change, drag an extra chromosome 21 onto a karyotype to make 47, and count mutated cells at different mutagen doses to plot a best-fit line.
Mutation as a change in genetic material: gene mutations (a base swapped, added or taken out, and the frameshift an added or lost base causes), using the sickle cell change in the beta-globin gene; a chromosome mutation, the extra chromosome 21 of Down syndrome (47 chromosomes) from an error in meiosis; and how ionising radiation and some chemicals increase the rate of mutation · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Mutation: teaching models of a gene, a karyotype and a dish of cells. A mutation is a change in the genetic material. A gene mutation changes the order of bases in a gene: a base swapped (substitution), added (insertion) or taken out (deletion). Bases are read in triplets from the start, so a swap changes only one triplet (at most one amino acid, or an early stop), but an added or lost base shifts every triplet after it (a frameshift). A chromosome mutation changes the number (or structure) of chromosomes: in Down syndrome body cells usually have 47, with three copies of chromosome 21. Mutations happen at random; ionising radiation and some chemicals increase the rate. Most mutations have no effect, some are harmful, and a few are useful. Simplified on purpose: only the first 10 triplets of the real beta-globin gene are shown and read, from strand 1 with T read as U (the mRNA copy and the ribosome are not drawn); the start triplet is locked, and one change is made at a time; the karyotype is a drawing to scale by length, with plain shapes in place of the stained bands; the dose model is made up (model units, 2 in 100 cells at dose 0, doubling at dose 1); real mutation rates for one gene are far lower; the bench pieces are teaching models, not real objects at any one scale.
- Glow: the model in use; lit part: the extra chromosome 21
- Close-up: the gene, the karyotype or the dish, one at a time
- Dashed outline: where you can drop the piece you hold
Use it in your lessons
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