30 8 (a) Haemophilia is a sex linked, genetic condition that prevents blood clotting. XH is the allele for blood clotting Xh is the allele for haemophilia The pedigree diagram shows a family that has individuals who have haemophilia. Key male with haemophilia male without haemophilia female with haemophilia female without haemophilia 1 2 3 4 5 7 6 8 9 10 11 (i) What are the genotypes of individuals 1 and 2? (1) A XHY and XHXH B XhY and XHXh C XhY and XHXH D XHY and XHXh Turn over 31 (ii) Use a genetic diagram to determine the probability that the next child of individuals 4 and 5 will be a boy without haemophilia. (3) Answer.............................................................. 32 (b) Kidney dialysis machines are used to remove urea from the blood of patients who are suffering from kidney disease. Anti-clotting drugs are given to patients to reduce the risk of blood clot formation whilst undergoing kidney dialysis. The potential use of two anti-clotting drugs, Drug A and Drug B, was investigated. Blood samples were taken from 20 healthy adults and placed into test tubes. The times taken for the blood samples to clot after addition of 2 mg dm−3 of Drug A were recorded. This was repeated with Drug B and again with a control. The results are shown in the graph. Time taken for blood to clot / s 600 500 400 300 200 100 0 Control Drug B Drug A Drug type mean mean mean Turn over 33 It takes 40 minutes for Drug A to become inactive in a person and 110 minutes for Drug B to become inactive. Analyse the data to discuss the use of Drug A and Drug B to prevent the formation of blood clots. 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(Total for Question 8 = 9 marks) 34 BLANK PAGE