Solutions to these questions can be found here. 1) The following pedigree shows the inheritance of a disorder. Which row of the table shows the genotypes of individuals 1 and 2? 2) Colour blindness in humans is determined by a sex-linked gene. Two family trees are shown. Which row of the table shows the probability of colour-blind offspring of each sex if individuals 1 and 2 were to have children together? 3) Lynch syndrome is an autosomal dominant condition that is the result of a mutation of a DNA repair gene. This mutation interferes with the ability of DNA to repair itself. The incidence of cancer in a family with Lynch syndrome is shown in the pedigree. Analyse the disease pattern shown in the pedigree. (3 marks) 4) A pedigree chart of an inherited characteristic is shown. Subsequent genetic analysis showed I - 2 does not have the recessive allele. Explain the inheritance of this characteristic. (3 marks) 5) The pedigree shows the inheritance of a characteristic. What pattern of inheritance is shown? A) Dominant and sex-linked B) Recessive and sex-linked C) Dominant and not sex-linked D) Recessive and not sex-linked 6) A non-infectious disease was observed in a mother and her four sons who live with her. She has no daughters. The father of these children does not have the disease and does not live with them. The woman’s parents and her two sisters who live overseas do not have the disease. a) Her doctor suspects that the disease is NOT inherited. Identify data that could be collected to investigate a non-inheritable cause of the disease. (1 mark) b) A geneticist suspects that the disease is inherited. Draw the family pedigree for this disease. (2 marks) c) From the evidence, what indicates that the disease could be the result of a recessive allele and not be sex linked? (2 marks) 7) A pedigree is shown. What type of inheritance is shown in the pedigree? A) Sex-linked recessive B) Sex-linked dominant C) Non sex-linked recessive D) Non sex-linked dominant 8) The pedigrees show the inheritance of two genetic disorders in the same family. Person 8 is not a carrier of the vision defect. a) Predict whether genes for each of these defects are dominant or recessive. (1 mark)
b) Individuals 9 and 10 have requested genetic counselling. Predict the possible ratios of the phenotypes of their children if the genes were linked. Predict the ratios if they were not linked. Show working. (4 marks)
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