Q35 - Multi-Locus Blood Typing to Resolve a Paternity Case

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Pedigree Analysis & Human Genetic Disorders

In a criminal case about rape, which was brought to court, four men (1–4; Table), the victim (Mother) and the resulting child (Daughter) (1-4, Table) were blood-type scored for ABO (alleles IA and IB are co-dominant, i recessive), Rhesus (allele Rh+ dominant to Rh−), MN (alleles M and N are co-dominant), and the X-linked Xg(a) (allele Xg(a+) dominant to Xg(a-)). Results are shown in the Table. Results of blood-type testing. Man 1–4 are potential fathers.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. Both Man 2 and Man 3 can be the father

B. The father could be identified unambiguously with less than four blood type systems

C. Using the ABO system alone, the daughter's genotype had to be IAi

D. If the daughter bears a boy with a man, whose genotype is Xg(a+), then her son must be Xg(a+), because the allele Xg(a+) is dominant

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Question reproduced from IBO 2015, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)