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Exam 3 Spring16 with answers (2).docx

Exam 3 Spring16 with answers (2).docx - Biology 355 Name...

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Biology 355 Name: Exam 3 1.) (6 pts) In class we studied the breast cancer susceptibility gene BRCA1 . CHEK2 is another breast cancer susceptibility gene. A research group studied the occurrence of breast cancer in a group of patients who were carriers for a specific mutant allele, CHEK2 *1100delC. One of the conclusions was that the mutant allele has low penetrance. What does low penetrance mean? What does it imply about a patient’s chance of getting breast cancer, or the seriousness of the disease? Low penetrance means that even if a person has the mutation, the probability of developing breast cancer is low. It tells you nothing about the seriousness of the disease. 2.) (6 pts) If all the genes in an organism were mutated and tested for linkage, how many linkage groups would be found in A.) a haploid organism with 17 chromosomes per cell? 17 B.) a virus (assume one molecule of nucleic acid)? 1 C.) a rat (diploid number = 42)? 21 3.) (6 pts) The genes dumpy ( dp ), clot ( cl ) and apterous ( ap ) are all on chromosome 2 of Drosophila . In a series of 2-point mapping crosses the following genetic distances were determined: dp – ap 42 dp – cl 3 ap – cl 39 Draw the genetic map. dp ____ cl _______________ap 3 39
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4.) (36 pts) In Drosophila , Dichaete , pink (eye color) and ebony (body color) are on chromosome 3, in that order. The Dichaete allele causes an abnormal wing shape. It is dominant over wild type, and it is lethal when homozygous. Flies from a Dichaete + + stock were crossed to a + pink ebony stock. The + pink ebony stock breeds true.
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