hmb265 midterm exam 2012-13-short answer and figures-posted
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genetics examTRANSCRIPT
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HMB265H1F Midterm Exam 2012-13 Name_______________________________ Student #______________________
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Part 2 SHORT ANSWER. Write your answer in the space provided. (1 question with 2 parts, worth 4 marks total) 18) Michael has red-green colour-blindness, an X-linked recessive trait, and he wants to know the probability of his children being red-green colour-blind. a) (2 marks) If the frequency of the red-green colour-blind allele in the population is 10% and Michael mates randomly, what is the probability that Michael's daughter has the disease? Show your work. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ b) (2 marks) Why is red-green colour-blindness found typically at much higher frequencies in populations compared to other X-linked disorders? Explain your answer using one of the two main factors that determine the frequencies of genetic disease.
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MariaText BoxThis is equivalent to the probability that: 1) Michael's partner is heterozygous for the disease AND she passes it on. Heterozygous probability is: 2 x 0.9 x 0.1 x = 0.09 or 9% (1 mark)2) Michael's partner is homozygous = 1% Probability of the daughter having the disease: 1% + 9% = 10% (1 mark)
MariaText BoxThe frequency of a disorder will be a function of the strength of selection and the mutation rate. Red-green colour-blindness probably has little to no selective disadvantage, and so therefore can be common in a population compared with diseases that reduce survival and reproduction. (2 marks)Alternatively (for 1.5 marks), the mutation rate might be high at genes causing red-green colour-blindness.
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HMB265H1F Midterm Exam 2012-13 Name_______________________________ Student #______________________
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HMB265H1F Midterm Exam 2012-13 Name_______________________________ Student #______________________
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Total Pages = 7 Total Marks = 38