lab 3b - Dhaval Rana AP Biology Lab 3B What is the Effect...

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Dhaval Rana AP Biology November 10, 2009 Lab 3B: What is the Effect of Crossing Over on Meiosis Abstract: The purpose of lab 3b was to find the crossover frequency and map distance in sordaria fimicola. Sordaria fimicola is an ascomycete fungus that can be used to demonstrate the results of crossing over during meiosis. From past knowledge, it can be concluded that if sordaria are going through meiosis, then the number of asci showing crossing over will be larger than the number of asci not showing crossing over. The number of asci is counted in the slides of sordaria fimicola to see which is going through cross over and which are not in order to find the percent of crossovers and map distance. The results support the hypothesis that if sordaria are going through meiosis, then the number of asci showing crossing over will be greater than the number of asci not showing crossing over and the accepted values of the percent crossover and map distance. Introduction: Meiosis means to make something smaller. It is a reduction division that produces genetically different daughter cells that have half the genetic information of the parent. During the process of meiosis, the genome of the diploids begins to undergo two distinct rounds of division that ultimately result in the four haploid cells. Each of the haploid cells or gametes will contain one fully complete strand of chromosomes, which equates to half of the chromosomes supplied by the previous division. The gametes are capable of meshing or fusing with other opposite gender haploid cells during the process of fertilization. In meiosis I, the chromosomes come together in a process called synapsis. Synapsis is the side by side pairing of homologous maternal and paternal chromosomes at the start of meiosis. During this process, crossing over occurs where the chromatids of homologous chromosomes exchange parts. In lab 3, the number of asci is counted. The asci had spores that are either black or tan. If there is a 4:4 pattern of the black and tan spores of the asci then no crossing over occurred. However, if there is a 2:4 or 2:2:2:2
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lab 3b - Dhaval Rana AP Biology Lab 3B What is the Effect...

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