page 11 18. Haemophilia A is a sex-linked condition that slows blood clotting. The allele for normal clotting (XH) is dominant to the allele for haemophilia A (Xh). The diagram gives information about the inheritance of haemophilia A in one family. unaffected grandmother P affected grandfather Q unaffected grandmother R unaffected grandfather S unaffected mother unaffected father unaffected daughter affected son From the information given, which of the statements is true? A The genotype of grandmother P must be XHXh but the genotype of grandmother R cannot be determined. B The genotype of neither grandmother can be determined. C The genotype of both the unaffected mother and her daughter must be XHXh. D The genotype of neither the mother or her daughter can be determined. [Turn over