Selective breeding sim
Drag the two parent tags onto the tomato plants you choose, cross them one generation at a time, record the mean fruit mass, and compare with parents picked at random.
Selective breeding (artificial selection) in tomato plants: choosing parents with a wanted characteristic over several generations, the rise and levelling off of fruit mass as genetic variation is lost, inbreeding and a recessive disease allele, and the difference from natural selection · covers the IGCSE, GCSE topic
What the sim shows
A teaching model of selective breeding in tomato plants; illustrative numbers, not real data. Fruit mass is controlled by 8 genes with two alleles each, B and b: every B allele adds 10 g to a base of 20 g (20 to 180 g), the genes add up with no dominance and are inherited independently; real fruit size depends on many genes of unequal effect. The environment adds a random change with a spread of 6 g (never more than 15 g either way), which is not inherited. Leaf-mould resistance is one gene, R (dominant) and r: only rr plants get leaf mould, and leaf mould does not lower fruit mass in this model (real diseased plants give less fruit). Each generation has 12 plants; every cross uses two different plants and gives 12 offspring, each with one allele of every gene from each parent, chosen at random (no self-pollination). A seeded model: a fixed list of random numbers, so the same steps always give the same plants. Every run starts from the same 12 plants. A real tomato generation takes a growing season; here one click.
- Parent tag: marks a plant you chose as a parent (drag the tags in the close-up)
- Close-up: the 12 plants of this generation, each with its fruit and fruit mass
- Ring: a plant chosen as a parent, in the dot plot of fruit masses
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
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