Purpose and Background Cells divide in two ways, mitosis and meiosis. Mitosis is used to produce cells that are genetically identical to the parent cell for growth, asexual reproduction, or repair after injury. Cells that are produced by mitosis are diploid, meaning that they have two complete sets of chromosomes, one from each parent. Meiosis is used to produce haploid cells that have only one set of chromosomes, a mix of chromosomes from both parents. Meiosis produces cells that are genetically unique from their parent cells. Unique haploid cells are produced in part by crossing over, which occurs in prophase I on meiosis. Crossing over is the process by which during synapsis, homologous chromosomes exchange sets of DNA, resulting
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Press lightly on the cover slip to rupture the spore casings but not the asci.
7. Place the slide on the microscope.
8. Using 10x objective, find an area of hybrid asci.
9. Increase the objective up to 40x.
10. Record the images on the slide.
11. Count at least 50 asci for each cross.
12. Record results.
13. Calculate the percentage of asci that show crossing over.
14. Calculate the recombination frequency.
Hypothesis The percent of asci showing crossing over will be 56% before dividing by two in the wild type and gray Sordaria Fimicola cross due to the location of the spore color gene about halfway between the centromere and end of the chromosome. Thus, the distance between the gene and the centromere will be 28 map units.
Variables
• Dependent- Percent of crossover, number of asci showing crossover
• Independent- Distance from gene to centromere
• Control- Sordaria Fimicola culture, slide, time, strains being crossed, area viewed, temperature, microscope used, age of sample
Data
Under the microscope, we saw brown asci surrounded by and filled with small, almond shaped spores in two similar shades, gray-purple and black-purple. Some of the spores appeared darker because their color was distorted by the brown color of the remaining …show more content…
Additionally, all spores that were visible appeared to be about the same color. The results we found above were found using an online source to count asci showing crossover in photos of successful Sordaria labs. In our original lab, there were several factors that contributed to our failure to find asci filled with crossover or non-crossover ascospores. First, our petri dish for this lab contained only mutant gray Sordaria. Thus, it was impossible to count the number of asci showing crossover as there were not two fungi for crossover to occur between. Second, the Sordaria on our petri dish was not in the ascospore phase; it was in the spore discharge stage. Hence, there were very few asci left as the spores were being discharged from the asci and into their environment to be fertilized and increase genetic variation. Lastly, if we had had two strains of Sordaria to cross and if the Sordaria had been in the right life cycle, we would have struggled to count the number of asci showing crossover as we found it difficult to rupture the spore casings without rupturing the remaining asci. The online version of the lab supported my hypothesis because the percent of crossover was 56.52%, very close to my predicted 56% recombination before division by 2. Accordingly, both the predicted and actual distance between the gene and centromere were similar. Our results varied from the actual distance of 26
Press lightly on the cover slip to rupture the spore casings but not the asci.
7. Place the slide on the microscope.
8. Using 10x objective, find an area of hybrid asci.
9. Increase the objective up to 40x.
10. Record the images on the slide.
11. Count at least 50 asci for each cross.
12. Record results.
13. Calculate the percentage of asci that show crossing over.
14. Calculate the recombination frequency.
Hypothesis The percent of asci showing crossing over will be 56% before dividing by two in the wild type and gray Sordaria Fimicola cross due to the location of the spore color gene about halfway between the centromere and end of the chromosome. Thus, the distance between the gene and the centromere will be 28 map units.
Variables
• Dependent- Percent of crossover, number of asci showing crossover
• Independent- Distance from gene to centromere
• Control- Sordaria Fimicola culture, slide, time, strains being crossed, area viewed, temperature, microscope used, age of sample
Data
Under the microscope, we saw brown asci surrounded by and filled with small, almond shaped spores in two similar shades, gray-purple and black-purple. Some of the spores appeared darker because their color was distorted by the brown color of the remaining …show more content…
Additionally, all spores that were visible appeared to be about the same color. The results we found above were found using an online source to count asci showing crossover in photos of successful Sordaria labs. In our original lab, there were several factors that contributed to our failure to find asci filled with crossover or non-crossover ascospores. First, our petri dish for this lab contained only mutant gray Sordaria. Thus, it was impossible to count the number of asci showing crossover as there were not two fungi for crossover to occur between. Second, the Sordaria on our petri dish was not in the ascospore phase; it was in the spore discharge stage. Hence, there were very few asci left as the spores were being discharged from the asci and into their environment to be fertilized and increase genetic variation. Lastly, if we had had two strains of Sordaria to cross and if the Sordaria had been in the right life cycle, we would have struggled to count the number of asci showing crossover as we found it difficult to rupture the spore casings without rupturing the remaining asci. The online version of the lab supported my hypothesis because the percent of crossover was 56.52%, very close to my predicted 56% recombination before division by 2. Accordingly, both the predicted and actual distance between the gene and centromere were similar. Our results varied from the actual distance of 26