Determine the genotype of person 1.

Deduce the genotype of the mother of person 2.

If person 3 has a son, and the father is a hemophiliac male, predict the son’s phenotype.

Suggest how sheep could be genetically modified to help the treatment of hemophilia in humans.

X^HY

X^HX^h
Apply ECF if upper case and lower case forms of another letter are used to correctly denote hemophilia in female genotype.

normal (male) / not affected / no hemophilia
Do not accept X^HY by itself, since question asks for phenotype.

genetically modify sheep to produce (blood) clotting factors (e.g. factor IX) in milk

Needed the genotype X^HY; no credit was awarded to a word description such as normal male;  

Again the genotype is needed but easier to get than in i) since in X^HX^h it's not necessary to know if h is dominant or recessive;

Description of the boy's phenotype was needed e.g. normal or not affected or no hemophilia.

Almost no candidate could answer this question to the extent of gaining the mark. Though genetically modifying sheep to produce clotting factors was sometimes known, candidates failed to mention how the clotting factors became available to humans. That the clotting factors could be harvested from the sheep milk was a necessary piece of additional information. Surprisingly, some extremely weak candidates gave accurate thorough answers to this question (A.S.4.4.9).