In humans, the ABO system contains four blood groups: A, B, AB and O. The gene that controls blood group has three alleles: $I^A$, $I^B$ and $I^o$.
(a)[4]
Use the genetic diagram to work out the probability that the next child will have blood group O.
(b)[2]
Explain why the ABO blood group system is an example of co-dominance.
(c)[2]
With reference to Fig. 6.1, explain why the ABO blood group system shows discontinuous variation.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Gametes $I^A,\;I^B,\;I^O$ are shown accurately” …
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