What is the most likely genotype for the propositus in a family study related to blood antigens?

In assessing the most likely genotype for the propositus related to the Kidd blood group antigens, it is important to understand the inheritance and possibility of expression of these alleles. The Kidd blood group system comprises two alleles, Jka and Jkb, each of which can be inherited in various combinations.

The genotype JkbJk indicates that the individual has two Jkb alleles. Jk refers to a null phenotype, which is not one of the alleles involved in this system. Therefore, having a combination of Jkb with a non-functional or null allele signifies that the propositus can potentially produce antibodies against both Jka and Jkb antigens, provided that they do not express the Jka antigen effectively. This situation can arise in cases where the individual may have inherited two Jkb alleles, leading to an absence of the Jka antigen but presence of the Jkb antigen predominant.

This genotype is particularly relevant if the propositus has a history of transfusions or pregnancies that might lead to sensitization against the Jka antigen or if there is a known family history where the expression of the Jk(a–) phenotype is common. In a family study, exploring potential serological findings might reveal the propositus