Fig. 1 shows the blood groups of members of one family. A laboratory tested samples of red blood cells using blood-group antibodies. The mother has blood gr...
Question 1 Report
Fig. 1 shows the blood groups of members of one family. A laboratory tested samples of red blood cells using blood-group antibodies. The mother has blood group A, the father has blood group B and their first child has blood group O. The alleles for the ABO blood-group system are IA, IB and i. The child is healthy and has no blood disease.
(a) State the two alleles in the genotype of the child. [2]
(b) Complete the genotypes of the mother and father using the alleles IA, IB and i. [2]
(c) Explain why a person with blood group A and a person with blood group B can have a child with blood group O. [3]
(d) Which blood groups are possible for another child of these parents? [3]
Answer Details
(a) Blood group O has genotype \(ii\), so the child has one \(i\) allele from each parent. [2 marks]
(b) The mother is \(I^A i\) and the father is \(I^B i\). Each must carry \(i\), because they produced a child with \(ii\). [2 marks]
(c) Both parents are heterozygous and can pass an \(i\) allele to a child. If the child receives \(i\) from both parents, its genotype is \(ii\), producing blood group O. [3 marks]
(d) Possible blood groups are A, with \(I^A i\); B, with \(I^B i\); AB, with \(I^A I^B\); and O, with \(ii\). Any three gain credit. [3 marks]
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