Inheritance

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Question 35

Human blood group is an example of a phenotype determined by alleles that show codominance.

The table below shows the different blood groups and their genotypes:

Blood group	Genotypes
A	$I^A I^A\,$ or $I^A I^O$
B	$I^B I^B\,$ or $I^B I^O$
AB	$I^A I^B$
O	$I^O I^O$

Explain what is meant by the term codominance.

[1]

A woman with blood group A and a man with blood group B have a child with blood group O. Use a genetic diagram to show how this is possible. Your diagram should include:

Genotypes of the parents
Gametes produced by each parent
Genotypes of the potential offspring, and their corresponding phenotypes.

[4]

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