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Human Biology - Jane is an asymptomatic carrier of the...

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8c. What other testing options might help follow the DMD risk in this family if the DNA-based testing did not find a mutation but the clinical diagnosis is not in doubt? Linkage analysis CPK testing in females. 9. After testing Eli you identified a deletion of a portion of the gene and confirmed the diagnosis of DMD. One of Eli’s pregnant cousins comes to see you. She is the daughter of Jane, an estranged older sister that was not mentioned when the family history was originally obtained. The cousin would like to know what her chances are of having a boy with DMD before she considers whether to pursue testing. Using Bayes theorem determine the risk that her child will be born with DMD. The pedigree is modified below. One would first need to test the probability that
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Unformatted text preview: Jane is an asymptomatic carrier of the dystrophin mutation and has had 3 unaffected male children. Carrier Not a Carrier Prior ½ ½ Conditional ½ 3 = 1/8 1 (odds of having three normal boys) Joint 1/16 ½ Posterior probability is 1/16 _____________ = 1/9 1/16 + 8/16 The risk that Jane’s daughter is a carrier is: Carrier Not a Carrier Prior 1/18 (1/9 x ½ ) 17/18 [1 - 1/18] Conditional 1/2 1 (odds of having one normal boy) Joint 1/36 17/18 Posterior probability is 1/36 ____________ = 1/35 1/36 + 34/36 The probability that she will pass on the mutation is ½ and the probability that the child will be male is ½ so the probability she will have a son affected with DMD is 1/35 x ½ x ½ = 1/140 ....
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