Tetrad Analysis Lab

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Gene Mapping of Fungus Sordaria fimicola Using Tetrad Analysis
Devan Endejan

Biology 220
October 30, 2015

This lab is used to exhibit gene linkage and mapping with tetrad analysis. Gene mapping is when a method is used to determine how close two genes are, the closer the genes are the more likely those genes are inherited together. For the lab we used a fungus Sordaria fimicola, because this particular fungus produces spores that can be easily observed with tetrad analysis. Tetrad analysis is a method used for fungi to show linked relationships by evaluating the products from meiotic division. The asci of S. fimicola stay complete with tetrad analysis which makes the spores easily observed for genetic cross-over. This lab
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Eight ascospores are produced form one zygote, which are lined up in an ascus. The ascospores are haploid and all the alleles are phenotypically shown. The fungus Sordaris when normal has a spore color that is black. In this lab we will be using gray and tan spores to mate. The allele form for the gray spore gene is g+ which is the wild type allele, and the other is g, which is the mutant allele. The tan spore gene has a t+ for the wild type allele, and the mutant allele t. The black ascospores genotype is g+t+, gray will have the genotype g t+ and the tan will be g+t, and colorless genotype will be g…show more content…
We then flipped the dish and sectioned it off into 4 sections, which then were marked with the specific genotype that would be inoculated into that section. The initials of the group were also put on the dish. Then we used an inoculating loop to cut out sections of the fungus. The inoculating loop was sterilized with a flame and let cool down before touching the fungus. After cutting a block of the fungus, we placed it on the petri dished in the section that was appropriately marked for that specific strain. After the four sections were placed, the lid was placed on the petri dish, and then the dish was with tape to keep close, and wrapped in aluminum foil and placed into the correct bin to sit. After two weeks the petri dishes were ready to be observed. We used a toothpick to scrap lightly the top of the agar in the petri dishes, ensuring we were collecting from one of the dividing lines. With the spores on our toothpicks, we then smeared them onto a slide that was provided to us. We had distilled water that was lightly put on top of the smear to ensure that the cover slip would stick. After the cover slip was in placed we then got microscopes and set the stages and lighting to view the specimen. The spores were to be observed at a 4x magnification or 10X to see the color. We were to observe and record 30 asci and enter on computer spreadsheet, but asci with 8 spores of identical color were to
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