Bio 13 Lab Report

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In the four-week long experiment conducted in the Bio 13 Lab, we were able to conduct a genetic analysis of the yeast S. cerevisiae, particularly investigating the inheritance and linkage of three genes: HIS4, LEU2, and LYS2. In week one, a suspension of spores was received and aliquots of the suspension were plates onto two YPD plates. After a week of yeast growth, haploid spore clones were carefully picked from the plates by sterile toothpicks and used to make patches on a new YPD plate, the master plate. In week three, the master plate was replicated onto three dropout plates: -His, -Leu, and -Lys. In the final week, the growth of the patches on the dropout plates were analyzed and class data was collected in order to conduct calculations …show more content…
By the conclusion of the experiment, we determined which of three genes were linked and the distance between those linked genes. The first experiment involved in this four-week project was the plating of the suspension of spores and application of microscopy. This involved taking the suspension of spores that was already prepared by the Bio 13 staff and spreading the suspension onto two YPD plates by using sterile techniques. These sterile techniques included dipping the spreader used in plating into ethanol and then burning the ethanol off. The medium used in these plates was YPD-agar, which stands for Yeast Extract Peptone and Dextrose which is a complete, nutrient rich medium that has all the nutrients necessary for the growth of yeast, such as the S. cerevisiae used in this experiment. The most important component of this week’s experiment was the suspension of spores. Although not prepared by students, it is still critical to understand how it was …show more content…
We were given two samples, one of vegetative (asexual/budding) yeast cells and one of yeast cells that went through meiosis and formed tetrads. By familiarizing ourselves with the microscope, we had to determine which sample contained vegetative yeast cells and which contained tetrads. After first preparing both samples by creating glass slides for each sample, we then determined the identity of each sample. In sample #1, we observed distinct "packages" that each contained smaller subunits. Most of the time, these sacs appeared to have four circles in it, that we assumed were the spores. We concluded that sample #1 contained yeast that went through meiosis, as the spores (smaller subunits) are yeast 's gametes and yeast produces these tetrads of four spores in an ascus through meiosis. In sample #2, we observed cells that often had smaller buds coming off larger cells. There were some clumps of more than two cells connected, however most featured two cells (the mother and the budding daughter cells) isolated from the rest. We conclude that sample #2 contianed a vegetative culture of yeast , as these cells were reproducing asexually through budding, yeast 's means of

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