Review Session 3 Key

Review Session 3 Key - Review session problems for Oct. 16...

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Review session problems for Oct. 16 2011 On midterm, summer 2010: 1.) Individuals 3 and 4 in the pedigree above both have a family history of Xeroderma pigmentosum (XP), as illustrated. XP is a rare, hereditary condition causing frequent formation of skin cancers, which is fully penetrant. a. Based on this pedigree, which of the following is the most likely mode of inheritance for this trait? >i. autosomal recessive iii. autosomal dominant ii. X-linked recessive iv. X-linked dominant b. Based on your answer in part a, is the mutation responsible for Xeroderma pigmentosum in this family more likely to be a loss of function or gain of function mutation, and why? Loss of function, because recessive mutations are generally loss of function mutations c. Based on your knowledge XP from lecture and reading, why do XP mutations cause frequent formation of skin cancers (1 or 2 sentences)? XP mutations knock out components of the nucleotide excision repair system that fixes thymidine dimers that form as a result of UV irradiation (see lecture 6). Without this repair system, mutations in all genes will occur at a higher frequency including genes important for keeping cell from turning into cancer cells. d. What is the probability that each of the following individuals is a carrier for Xeroderma pigmentosum? 1:
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Review Session 3 Key - Review session problems for Oct. 16...

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