ABO inheritance sim
Drag allele tokens to give two parents their blood-group alleles, make their gametes, drag a blood group into each box of the Punnett square, and see the four equally likely children and the chance of each blood group.
Inheritance of the ABO blood groups: one gene with three alleles (multiple alleles) IA, IB and IO, codominance of IA and IB, IO recessive, genotype and blood group (phenotype), gametes carrying one allele each, Punnett squares and the expected blood groups of the children · covers the O-Level, IGCSE topic
What the sim shows
ABO inheritance: one gene for the ABO blood group with three alleles (multiple alleles), I A , I B and I O . Each person has two of them, one on each of a homologous pair of chromosomes. I A and I B are codominant: both are expressed, so I A I B is group AB. Both are dominant to I O , which is recessive: I A I O is group A, I B I O group B, and only I O I O is group O. (Cambridge IGCSE writes I O as I o , with a small o.) Each gamete gets one allele of the pair, and the Punnett square pairs each gamete of one parent with each of the other: the four boxes are equally likely, so I A I O × I B I O is expected to give 1 A : 1 B : 1 AB : 1 O, and I A I B × I O I O to give 1 A : 1 B. Simplified on purpose: illustrative: a teaching model of one gene, not real family data; one gene with three alleles in the population (I A , I B and I O ); each person has two; I A and I B are codominant, and both are dominant to I O ; the blood group is shown only as the antigens on the red cells; the antibodies in the plasma are left out here; each gamete is equally likely to carry either allele of the parent's pair; each parent is drawn with two gametes, one for each allele; a real person makes very many, half with each allele; meiosis is shown only as each gamete getting one allele of the pair; the four children in the close-up are the four equally likely boxes, not four real children: a real family can have any mix; the rhesus (Rh) blood group and rare variants of this and other genes are left out; the allele and antigen colours are a key, not real colours; the red cells are drawn much larger and simpler than real ones (about 7–8 µm across).
- Glow: the part of the bench for the step you are on
- Close-up: the parents' alleles, your Punnett square, the four equally likely children and the chance of each group
- Dashed outline: an empty place to drop something
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