IB Biology HL D3.2.9 Abo Blood Groups Questions

Apply codominance and recessive i inheritance to infer ABO genotypes, predict offspring phenotypes and interpret antigen compatibility in IB Biology HL D3.2.9.

Exam points

Explain how IA and IB are codominant while i is recessive, linking each ABO genotype to its blood-group phenotype.
Deduce parental genotypes and calculate offspring ABO genotypes, phenotypes or probabilities from family data and crosses.
Interpret ABO antigen and antibody evidence to determine blood-group or transfusion compatibility.

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Study D3.2.9—ABO blood groups conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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Variation in genetically inherited characteristics is the basis for evolution.

Outline the inheritance of blood types in the ABO blood system in humans.

a. i and I ${ }^{\mathrm{A}}$ and $\mathrm{I}^{\mathrm{B}}$ are alleles (of the blood group gene)
b. $I^{A}$ is dominant and i is recessive $/ I^{B}$ is dominant and i is recessive
c. Group O (only) with ii and Group A with $\mathrm{I}^{\mathrm{A}} \mathrm{i}$ or $\mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{A}} /$ Group B with $\mathrm{I}^{\mathrm{B}} \mathrm{i}$ or $\mathrm{I}^{\mathrm{B}} \mathrm{I}^{\mathrm{B}}$
d. $\mathrm{I}^{\mathrm{A}}$ and $\mathrm{I}^{\mathrm{B}}$ are co-dominant so Group AB with $\mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{B}}$
e. one allele/copy of the gene inherited from each parent/Punnett square showing this

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IB Biology HL D3.2.9 Abo Blood Groups Questions question 1