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Lab Report - Rough Draft(2)

Lab Report - Rough Draft(2) - Mapping the crossing over...

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Mapping the crossing over genes for spore in the fungus Sordaria Nikhil Thomas, April 8, 2008, Lon Ridgway Abstract The purpose of this experiment is to identify whether crossing over would occur for spores in the fungus Sordaria . In our experiment we performed a cross between wild-type black strains (+) of the fungus with a mutant tan strain (t). My group’s hypothesis was that crossing over would occur if both the (+) and (t) strains were placed in agar plates and incubated at 22 ˚ to 24 ˚ Celsius for a period of 7 days. Our results showed that 57.5% of asci underwent crossing over. These results support the conclusion that crossing over will definitely occur between the wild-type black and mutant tan strains in genes for spores of the fungus Sordaria . Finally our conclusion of the Sordaria experiment led to the acceptance of the null hypothesis because we had a degree of freedom 1 and probability 0.05. Introduction Sordaria fimicola , ascus formation requires both meiotic and mitotic division to produce eight haploid ascospores. Crossing over occurs during the first nuclear division of meiosis (meiosis I or MI) between non-sister chromatids of homologous chromosomes, resulting in recombination of genes on the two homologues. The greater the distance between the two genes on the chromosomes, the more likely that crossing over will occur between them. During ascus development, if no crossing over occurs in meiosis I, a 4+4 pattern is produced in the ascospores. On the other hand if crossing over occurs then there are two possible patters to look for: 2+2+2+2 or 2+4+2. Both these patterns are referred to as an MII pattern (Helms14-2). The purpose of this experiment was to carry out the crossing over of genes in fungus Sordaria between the wild-black type (+) and mutant tan (t) strains. The proposed hypothesis
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stated that crossing over would occur between the (+) and (t) strains in the spores of fungus Sordaria . This experiment contains elements of chromosome mapping. The purpose of gene mapping is to assign a gene to a particular chromosome, and also to determine a gene’s location with respect to other genes on that same chromosome. In our experiment we will be able to map the genes for spore color in Sordaria . Using linkage analysis, we will be able to determine the relative distance between the centromere and known mutant genes. Recombination creates new combinations of existing hereditary variations and is believed
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Lab Report - Rough Draft(2) - Mapping the crossing over...

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