PS2-11_Key - Bio D137 Human Eukaryotic Genetics J.L. Marsh...

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Bio D137 Human Eukaryotic Genetics J.L. Marsh F’11 PROBLEM SET #2 DUE Tues 10/4 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 thefollowing 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? Answer : [1] likely dominant (1point ). Because ~50% of all offspring from affected parents are samesegregation of 50% but its rare). X= M/+ Y = +/+ (1 point) [2] Likely recessive (1 point) . Unaffected parents having affected kids, two affected parents having allaffecteds and one affected parent having none. X=A/a Y = a/a (1 point) 1
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twins, 14 cases were recorded where the second twin was affected. A] What does this suggest about the mode of inheritance of this form of color blindness?B] 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 ( 1 point) because theparents were normal but the children affected. This is not consistent with a fully penetrant dominant mutation. In families with ACHM children, both parents are carriers. For dizygotic twins who are no more related than 2 brothers ( 0.5 point) , each child, has a 25% chance of getting the disease (0.5 point) . If 1 sib is ACHM, there is a 25% chance that the other will be. For monozygotic twins, there should be complete concordance assuming a fully genetic origin of the syndrome. 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 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 consistentwith inheritance a simple recessive trait. a]
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This note was uploaded on 12/13/2011 for the course BIOSCI 137 taught by Professor Staff during the Fall '11 term at UC Irvine.

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PS2-11_Key - Bio D137 Human Eukaryotic Genetics J.L. Marsh...

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