PS2+09+key - Bio D137 Human Eukaryotic Genetics th J.L....

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1 Bio D137 Human Eukaryotic Genetics J.L. Marsh F'09 PROBLEM SET #2 DUE Tues 10/6 by 4pm in the box, 5 th floor MH Pedigree Analysis 1]. In the following pedigrees, assume that the disease trait is rare in the population. Answer the following questions about each pedigree: a] What is the probable mode of inheritance for family 1 and for family 2 ie. Dominant or recessive? Why? b] What are the possible genotypes of individuals X and Y in each pedigree? [1] [2] X Y X Y Answer : [1] likely dominant. Because ~50% of all offspring from affected parents are affected segregation of 50% but its rare). X= M/+ Y = +/+ [2] Likely recessive. Unaffected parents having affected kids, two affected parents having all affecteds and one affected parent having none. X=A/a Y = a/a Twin Studies 2] People who suffer from autism are withdrawn and self-absorbed. In a study of 22 pairs of identical twins, both twins were autistic, and in all cases the parents were normal. With dizygotic twins where the pair was identified by finding an autistic child, in 10 of 42 pairs of twins, both twins were affected. What does this suggest about the mode of inheritance of autism? How do you explain frequency of concordance of the dizygotic twins? Answer In this study, the mode of inheritance seems to be by a recessive trait because the parents were normal but the children affected. This is not consistent with a fully penetrant dominant mutation. In families with autistic children, both parents are carriers. Each child, then, has a 25% chance of getting the disease. If 1 sib is autistic, there is a 25% chance that the other will be. Ascertainment 3]. V3 In studying the autosomal recessive disease, muscular dystrophy, a total of 106 families were identified by finding sibships with 1 affected child, (given the frequency in the population all of these families can be considered to be Aa x Aa). Of these families, 20 are single child
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2 sibships, 39 have two children, 36 have three children, and 11 have four children. A total of 130 affected individuals were observed in this group. I want to know whether this ratio consistent
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This note was uploaded on 10/27/2009 for the course BIO SCI 05580 taught by Professor Marsh during the Fall '09 term at UC Irvine.

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PS2+09+key - Bio D137 Human Eukaryotic Genetics th J.L....

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