Rhesus factor is an antigen present on the surface of red blood cells of Rhesus positive individuals. Rhesus positive (Rh⁺ ) is dominant to Rhesus negative (Rh^– ). A mother with Rhesus negative blood gives birth to a baby with Rhesus positive blood and there are concerns that subsequent pregnancies will trigger an immune response.

What are the genotypes of the mother and her first baby?

B

This was a good discriminator. There was some criticism that the question was not on the syllabus, but it tested their understanding of inheritance rather than a specific example in the syllabus. It was well answered by candidates.