Inheriting blood groups
Choose the mother's and the father's blood group genes and see, in a Punnett square, the chance of each blood group in their children.
Core concept
Blood group is controlled by one gene with three alleles, A, B and O; A and B are both dominant over O and show together in AB, and each child gets one allele from each parent at random
Topic: Heredity
Your blood group (A, B, AB or O) depends on markers on your red blood cell: The tiny building block that every living thing is made of. All key words, and it is inherited. One gene controls it, with three forms called alleles: A, B and O. Every person has two alleles, one from their mother and one from their father, carried on their chromosomes. A and B are both dominant over O, so AO gives group A and BO gives group B; only OO gives group O. A and B are codominant: AB gives group AB. When an egg or a sperm forms, it gets just one of the parent's two alleles, chosen by chance (Mendel's law of segregation). A Punnett square shows all the ways the alleles can join. Knowing blood groups matters for safe blood transfusion: group O can be given to all groups, and group AB can receive from all.
What you will learn
- Explain genes, alleles, genotype and phenotype using blood groups.
- Distinguish dominant, recessive and codominant alleles.
- Use a Punnett square to predict the chances of children's blood groups.
- Explain why blood groups must match in a transfusion.
Before you start
- Know that genes are carried on chromosomes, which come in pairs.
Materials
- Two coins or cards marked with alleles, to act out the cross
Equipment
- A blood grouping chart
Procedure
- Record the children of an AO mother and a BO father.
- Record the children of an AB mother and an OO father.
- Record the children of two OO parents, and of an AA mother and a BB father.
How this simulation is simplified
- Each parent passes on either of their two alleles with an equal chance.
- Only the ABO gene is shown; the Rh factor (+ or −) is inherited separately.