Sordaria Formal Lab Report PDF

Preview

Summary

Sordaria Formal Lab Report...

Description

1 Introduction

Sordaria fimicola is a fungus that is a part of the Ascomycota phylum and is usually found in the feces of herbivores animals. (Maxwell, 2016). S. fimicola fungi is proved to be a good model organism in genetics to study how variations are produced by observing the life cycle of the organism as a whole (Campbell and Baynes, 2011). The organism undergoes the process of meiosis to reproduce. It begins by merging the two haploid spores (that are in the non-mating stage) to produce a zygote with diploid nucleus. The diploid zygotes then go through meiosis to produce ascospores which are 8 haploid spores found in the ascus of the organism (Saleem and Nevo, 2011). Several asci develop in the reproductive structure known as perithecium (Saleem and Nevo, 2011). Crossing over in meiosis (Metaphase I) plays an essential role in the S. fimicola lifecycle. Crossing over occurs when the genes are exchanged by the maternal and paternal chromosomes, resulting in a recombinant (Kalogeropoulos and Thuriaux, 1985). The end result of this process consists of completely new combination of genes (Bozeman, 2013). One of the form of genetic variability in S. fimicola is the phenotypic color of the ascospores caused by the production of melanin. The arrangement of ascospores in the ascus represents if the crossing occurred.

The objective of this lab was to define the variation in gene map distance under different experimental circumstances for the fungi Sordaria fimicola (Maxwell, 2016). To conduct this experiment, cross between a mutant and wildtype strains was performed. Three spore color mutant strains were used, the normal spore color for S. fimicola which is black, the mutant genes tan and gray color. Over the course of 5 days, the sample of the organism was stored in an incubator to allow crossing over between the wildtype and mutant strains. By categorizing the final amount of genes, the ruptured asci displayed a 4:4 ratios of non-recombinant and 2:2:2:2 or

2 2:4:2 ratio of recombinant genes. Hypothesis of this experiment is if the environment alters then the frequency of recombination fluctuates. Method and Materials Agar petri dish were divided into four quadrants by setting two sections of black (wildtype) S. fimicola strains interchanging with two sections of gray S. fimicola strains. The same process was repeated on the new agar dish, interchanging with two pieces of tan S. fimicola strain. Both of the dishes were placed in an incubator for five days at the room temperature. The compressed sample were prepared by collecting perithecia from the intersection of the two newly developed strains with the sterile inoculating loop. The samples were placed under the microscope slide with a drop of water and a cover slip over it. They were viewed under the microscope (10X objective) to observe the recombinant pattern of the ascospores. The non-recombinant (4:4 pattern) and recombinant asci (2:2:2:2 or 2:4:2 pattern) were counted to further calculate the percentage of asci showing crossover. The percentage was calculated by dividing the recombinant number by the total amount of asci and then multiplied by 100. The map distance was also calculated by dividing the percentage of crossover asci by 2. Results In order to analyze and measure the distance between the gene and the centromere, the recombinant and non-recombinant asci data was gathered using the microscopic image of S. fimicola ascospores (Fig .1). Overall, 24 asci were counted by adding 12 non- recombinant asci and 12 recombinants. To calculate the percentage of recombinant asci, crossovers were divided by the total number of asci and multiplied by 100, resulting in 50%. The gene map distance was

3 calculated by dividing the 50% of recombinant asci by 2 as mitosis occurred in S. fimicola. The gene to centromere distance resulted in 25 map units (Table 1).

Figure 1 Microscopic Image of S. fimicola Ascospores

Figure 1. Microscopic Image of S. fimicola Ascospores. Exploded image of asci was used to gather and analyze data to better understand the gene map units (Maxwell, 2016).

Table 1: Individual Data Analysis Non

Recombinant

Total No. of

% of

Gene to

Recombinant

Asci

Asci

Recombinant

Centromere

Asci

Distance

50

25

Asci

12

12

24

4 Table 1. Individual Data Analysis. There was a 4:4 ratios for parental asci (no crossing over) and a 2:2:2:2 or 2:4:2 ratios when crossing over occurred. The average asci crossing over (recombinant) frequency was 50% and the map distance from the gene for spore color and the centromere was 25.

Discussion In general, the recombinant genes are fabricated by the environment when different genes are acquired by the organisms based on the need of survival, and adaption to the environment. In this experiment, ruptured asci were observed to gather data and calculate gene map distance. Based on the individual data analysis, the average recombinant frequency was 50% and the gene to centromere distance was 25 map units. The hypothesis was correct as the environment played a big role in the change in recombination frequency. Although, it was unexpected to see 25 map units compared to the accepted average 26 map units. This slight difference may be possible that the sample was used for this experiment was not large enough or the sample was pressed hard which could result in breakdown of the ascospores. Another possible source of error could be that S. fimicola or the equipment used for this experiment was contaminated, may be not enough time was allowed for the strains to develop resulting is less accurate result. Overall, this lab helped in better understanding of how genetic variation is necessary to survive in the environment. This process is crucial to the life on this planet.

5

Citation Bozeman Science. (n.d.). The Sordaria Cross. Retrieved June 18, 2016 from https://www.youtube.com/watch?v=gXUxH1aFRp0 Kalogeropoulos, A., & Thuriaux, P. (1985). Gene conversion at the gray locus of Sordaria fimicola: fit of the experimental data to a hybrid DNA model of recombination. Genetics, 109(3), 599–610. Retrieved June 18, 2016 from http://www.ncbi.nlm.nih.gov/pubmed/3979816

Maxwell, R. (2016). Lab Experiment 1: Microscopes, Retrieved June 18, 2016 from https://gsu.view.usg.edu/d2l/le/content/1159725/viewContent/18013348/View Maxwell, R. (2016). Lab Experiment 1: Microscopes, Retrieved June 19, 2016 from https://gsu.view.usg.edu/d2l/home/1159725a Newcombe, G., Campbell, J., Griffith, D., Baynes, M., Launchbaugh, K., & Pendleton, R. (2016). Revisiting the Life Cycle of Dung Fungi, Including Sordaria fimicola. PloS One, 11(2), e0147425. Retrieved June 18, 2016 from http://doi.org/10.1371/journal.pone.0147425 Saleem, M., Lamb, B. C., & Nevo, E. (2001). Inherited Differences in Crossing Over and Gene Conversion Frequencies Between Wild Strains of Sordaria fimicola From “Evolution Canyon.” Genetics, 159(4), 1573–1593. Retrieved June 19, 2016 from http://www.genetics.org/content/159/4/1573...