CAIE IGCSE Biology 17.4.15 ABO Blood Group Inheritance

Practise applying IA, IB and Io alleles to blood-group genotypes, codominance and offspring probabilities.

Exam points

map IAIA or IAIo to group A, IBIB or IBIo to group B, IAIB to AB and IoIo to O
state that IA and IB are codominant while Io is recessive to both
complete parental crosses to calculate a child's blood-group probability or infer parent genotypes

[Maximum number: 2]

Fig. 6.1 is a photomicrograph of a blood clot.

Fig. 6.1

There are four blood group phenotypes A, B, AB and O in humans.

State the two possible genotypes for a person who has the phenotype blood group A .

1

2

$I^{A}I^{A}$

OR

$I^{A}I^{O}$

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