PS5-11Key - Bio D137 Human and Eukaryotic Genetics Prob Set...

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Bio D137 Human and Eukaryotic Genetics J.L.Marsh F'11 Prob Set 5 due Oct, 28 Name/student ID:_______________ 1 1 Deficiency mapping 1] Several enzymes and proteins a, b, c, d, e, f are known to be coded in a region near a locus of interest on chromosome 22 in humans, but their order is unknown. Patients with sporadic symptoms were analyzed and karyotyping identified 5 patients with deficiencies (deletions) on this arm of chromosome 22. The level of gene product being expressed was determined using biochemical and immunological techniques. The level of gene activity is indicated below as a percent relative to the activity observed in non-deletion bearing control persons. The data are: a b c d e f Pt 1 57 101 103 51 46 53 Pt 2 52 98 101 105 51 99 Pt 3 48 52 50 103 49 52 Pt 4 95 98 46 96 52 99 Pt 5 103 51 52 100 57 102 a) Use these data to determine the order of these genes on chromosome 22. Answ:9 pts b c e a f d | b | c | e | a | f | d Del3= (a, e, d, f) ------------------------------------ Del5= (a, e) ------------------ Del4= (a, b, c, e ,f) --------------------------------------------- Del2= (c, e) ------------------ Del1= (b, c, e) --------------------------- b) What gene most likely is responsible for the disease? Answ: e - because it is the only absent gene in all 5 patients because of the deletions. Cytogenetics 2] Zohary and Brown discovered a long inversion in a lily species and cytologically studied plants heterozygous for the inversion. They found 252 cells in diakinesis with one chiasma in the inversion and one chiasma outside of the inversion. These cells were examined in anaphase I showing 131 cells with one bridge (type A below) and 121 cells with a loop (type B below). What types of inversions and crossover events would give rise to each of these configurations? Show your reasoning and document your conclusion. Keri Reigle, an 8- year-old with chromosome 22q11.12 deletion syndrome, participated in UC
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Bio D137 Human and Eukaryotic Genetics J.L.Marsh F'11 Prob Set 5 due Oct, 28 Name/student ID:_______________ 2 2 A B ANSWER a) The two figures A&B could be caused by different double crossover types in a paracentric inversion. Type A bridges are caused by 2 and 4 strand double crossovers in a paracentric inversion that contains a chiasma in the inversion and a chiasma proximal to the inversion (i.e. proximal always refers to the centromere so proximal to the inversion is nearer to the centromere than the inversion loop thus between the inversion loop and the centromere). Type B figures arise from 3 strand double crossovers with the two crossovers in the same relative positions as in A (i.e. 1 in the loop and one between the loop and centromere).
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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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PS5-11Key - Bio D137 Human and Eukaryotic Genetics Prob Set...

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