Genetics and heredity — Question 25

QUESTION 25 (3 marks)

In blood group inheritance in humans, three alleles (i, I^A and I^B) determine blood type, which can be type O, A, B or AB. It is known that:

• allele I^A produces type A and is co-dominant with allele I^B, which produces type B

• allele i produces type O

• alleles I^A and I^B are dominant over allele i. A father who is heterozygous type A and a mother who is heterozygous type B have children. Predict the likely frequency of phenotypes for their offspring. Show your working.