Three-Generation Pedigree and ABO Blood Type Inheritance
Integrated ScienceGenetics & EvolutionAges 14–15
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Genetics & Evolution
A three-generation family pedigree: squares are males, circles are females, and filled shapes mark affected individuals. Tap any individual and the simulation infers their possible genotype with an explanation. Switch between a recessive-gene and a dominant-gene hypothesis to see why the dominant hypothesis conflicts with the pedigree, since unaffected parents still have an affected child. In blood-type mode, choose the ABO genotypes of the father and mother and simulate offspring: a gamete cross table for Iᴬ, Iᴮ, i gives the theoretical blood-type ratio, and a bar chart compares it with the experimental ratio from simulating many children.
Lesson: Human Genetics: Pedigrees and Blood Type
What it shows
Pedigree charts let geneticists work out how a trait is inherited without breeding experiments. If two unaffected parents have an affected child, the allele must be recessive and both parents must be heterozygous carriers; a dominant autosomal allele would require at least one affected parent. ABO blood groups show multiple alleles: Iᴬ and Iᴮ are codominant and both dominant over i, so parents with genotypes Iᴬi and Iᴮi can have a group O child. A gamete table gives the expected ratios, and observed ratios approach them only as the number of offspring grows.
How to use
In pedigree mode, tap each individual to read the inferred genotype and the reasoning, starting from affected people. Press Switch dominant/recessive to test the other hypothesis and ask students to find where it contradicts the chart. Then choose Switch to blood type, set the Father's blood-type genotype and Mother's blood-type genotype, and press Simulate N children several times. Increase the Number of children simulated each time to compare the experimental and theoretical bars.
Parameters you can change
- Content Three-generation pedigree, infer genotype, Offspring ABO blood type
- Hypothesis about the disease-causing gene Disease caused by a recessive autosomal gene, Disease caused by a dominant autosomal gene
- Father's blood-type genotype IᴬIᴬ – group A, Iᴬi – group A, IᴮIᴮ – group B, Iᴮi – group B, IᴬIᴮ – group AB, ii – group O
- Mother's blood-type genotype IᴬIᴬ – group A, Iᴬi – group A, IᴮIᴮ – group B, Iᴮi – group B, IᴬIᴮ – group AB, ii – group O
- Number of children simulated each time 20–400 children
Questions to explore
- Can a father with genotype Iᴬi and a mother with genotype Iᴮi have a group O child? With what probability?
- Which feature of the pedigree shows that the disease is caused by a recessive allele?
- Why do the experimental ratios get closer to the theoretical ratios as more children are simulated?
