16 5 Haemophilia is a condition that results in excessive bleeding due to a lack of blood clotting factors such as factor 8. It is an X‑linked recessive condition and one cause is a mutation to the F8 gene. (a) (i) Complete the diagram, by drawing a line, to show a possible locus for the F8 gene. (1) X chromosome Y chromosome (ii) Explain with the use of a genetic diagram why males with haemophilia cannot pass on this condition to their male offspring. 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Turn over 17 (b) There are 2931 mutations to the F8 gene that have been identified. Haemophilia can also be caused by a mutation to the F9 gene. There are 1133 mutations to the F9 gene that have been identified. Haemophilia is not classed as a polygenic disorder. (i) Give the meaning of the term polygenic. 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(ii) There are 575 identified mutations to the F9 gene that cause severe symptoms of haemophilia. The same percentage of these types of mutation is found in the F8 gene. Calculate the number of mutations to the F8 gene that produce severe symptoms. (2) Answer .............................................................. (Total for Question 5 = 9 marks)