Theory question 104
VariationA survey to determine blood groups was carried out on 250 people living in a community. The results are represented in the table below.
Blood group A: 8.0%; Blood group B: 14.0%; Blood group AB: 32.8%; Blood group O: 45.2%.
(a)(i) Explain the term co-dominance. (ii) Calculate the number of individuals with co-dominant blood group.
(iii) What is the total number of individuals in the table that are able to donate blood to an accident victim with blood group B?
(b) A man whose blood group is heterozygous A is married to a woman whose blood group is AB. With the aid of a genetic diagram, suggest the possible blood groups of their children.
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(a)(i) Co-dominance is when both alleles in a heterozygote are fully expressed in the phenotype, neither being dominant over the other, e.g. blood group AB.
(ii) Co-dominant group is AB: 32.8/100 × 250 = 82 individuals.
(iii) A group B person can receive from groups B and O: (14.0 + 45.2)/100 × 250 = 59.2% × 250 = 148 individuals.
(b) Man IAIO × woman IAIB; gametes IA, IO and IA, IB; offspring IAIA, IAIB, IAIO, IBIO; blood groups: A (IAIA and IAIO), AB and B, in the ratio 2 A : 1 AB : 1 B.
Convert each percentage to a number of people by multiplying by 250 and dividing by 100.