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Adil Sabir
Bio 110H
18 October 2014
Sordaria Lab Report
I. Introduction
Sordaria Fimicola reproduce through the process of meiosis. This process entails
prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II,
and telophase II. During the metaphase I stage, a crucial process called crossing over
occurs. Crossing over is the process by which genes and genetic material are exchanged
between homologous chromosomes and therefore create genetically variable offspring
(Lab Manual Pg.33). “Evolution Canyon” is a natural microscale laboratory where the
South Facing Slopes (SFS) receive more sunlight and the North Facing Slopes (NFS) are
more temperate and have more shade. After testing and research, there was determined to
be a higher crossover frequency in the SFS yet scientists were unsure whether this was
because of their environmental conditions or another external factor (Lab Manual pg.36).
According to Dr. Minou Nowrousian, Sordaria is a model organism to use
because they reproduce quickly, have a short life cycle, have distinct parts that are easy to
view under microscopes, and have multiple mutant strains that serve as markers for
different meiotic events (Nowrousian, 2010). We performed this experiment and
reproduced the Sordaria in identical conditions in order to determine if these results
deviated from those recorded in their natural habitat faced with different environmental
factors. While our main research question was to see if there was a difference between
the total recombinant asci and crossover percentage between the Sordaria in “Evolution
Canyon” and the Sordaria in our lab, our goal was to provide a baseline for future studies
and experiments. While we cannot draw conclusions about crossover frequency in harsh
conditions, we can, however, draw conclusions about our data as a baseline for
experimental conditions. With our experimental data, we can determine if the difference
in crossover frequencies occurred due to environmental factors and weather conditions or
due to some other factor. We predict that the crossover frequencies will be identical
under optimal, identical conditions.
Of the Sordaria that were reproduced, there could have been three different types
of asci created. The non recombinant 4:4 (Type A) is when there are four tan spores next
to four wild type spores. The recombinant 2:4:2 (Type B) is when chromosomes two are
stacked on top of each other and recombination creates two tan spores followed by four
wild type spores and then two more tan spores or vice versa. The other recombinant
2:2:2:2 (Type C) is when two chromosomes line up next to each other and recombination
causes spore color alternates after every two spores.
Some main research questions arise before conducting this experiment. What
evidence demonstrates cross over between the spore color gene and centromere and what
is the crossover frequency of the spore color gene with the centromere in organisms
grown under optimal conditions? How does environmental stress affect cross over
frequency, structures associated with meiosis, and gene expression related to meiosis?
squash the spores which we then were able to view the recombination ratios of under a
microscope (Lab Manual Pg.42).
We added together the number of 2:2:2:2 and 2:4:2 alternating asci to get a total number
of recombinant asci and totaled the number on 4:4 non recombinant asci and then were able to
calculate the percent crossover and map distance by using the formulas: Percent Crossover = (#
recombinant asci/total # asci)x100 and Map Distance = % crossover/2.
III. Results
Table 1: Individual Data
Non Recombina nt
Recombinant Recombinant Total # of Asci Total # of Recombinant Asci
of Type A
Asci (4:4)
of Type B
Asci (2:4:2)
of Type C
Asci (2:2:2:2)
(Lab Manual pg.56)
Table 2: Small Group Data
Non Recombina nt
Recombinant Recombinant Total # of Asci Total # of Recombinant Asci
of Type A
Asci (4:4)
of Type B
Asci (2:4:2)
of Type C
Asci (2:2:2:2)
(Lab Manual pg.56)
Table 3: Combined Section Data
Non Recombina nt
Recombinant Recombinant Total # of Asci Total # of Recombinant Asci
of Type A
Asci (4:4)
of Type B
Asci (2:4:2)
of Type C
Asci (2:2:2:2)
(Lab Manual pg.57)
Table 4: Combined Course Data
Non Recombina nt
Recombinant Recombinant Total # of Asci Total # of Recombinant Asci
of Type A
Asci (4:4)
of Type B
Asci (2:4:2)
of Type C
Asci (2:2:2:2)
(Lab Manual pg.57)
Table 5: Combined Section Data Analysis
Non Re combin ant
Recomb inant
Recomb inant
of
Total Asci
of
Total Recomb inant Asci (B+C)
Frequen cy of Recomb inant Asci(B +C/Tota l)
Frequen cy of Type B Asci (B/Tota l)
Frequen cy of Type C Asci (C/Tota l)
Ratio B/C
of
Type A Asci (4:4)
of
Type B Asci (2:4:2)
of
Type C Asci (2:2:2: )
(Lab Manual pg.58)
dark environment. Some problems we faced when preparing the squash slides were pushing
down too hard on the slide so the perithecia scattered everywhere, or pushing down too lightly so
the spores do not burst. We were able to determine that crossover did occur between the spore
color gene and centromere since we counted a certain number of recombinant asci and
recombination occurs due to crossing over (Lab Manual pg.59). In addition, we found that there
is a 57.2% crossover overall which is fairly close to 50% which is what we predicted. Although
it is not 50%, we can't say this isn't typical for standard lab conditions.
The deviation of this percentage could be due to random selection of asci. Since this
percentage is so close to 50% and the actual percentages in “Evolution Canyon” have a mucher
greater percentage in crossover in SFS than NFS, we can conclude that percent crossover,
meiosis, and gene expression in Sordaria is variable. Our data that we collected can be useful in
comparing against data collected from future experimental conditions. The map distance, which
is half the percent crossover, is equal to 28.6. The frequency of crossover in Type B was 26.8%
which is very close to the 30.4% in type C. The ratio of B to C was .88 which is very close to 1.
The deviation of these percentages again could have been due to random selection of spores from
the agar. Since these numbers are so close, we can determine that crossover frequency in Type B
and Type C is essentially identical.
We learned that gene expression and crossover frequency in Sordaria is variable.
However, we only tested this hypothesis on just one type of Fungi. We can do further
experiments to see if this was also true in more complex animals such as mammals, reptiles, or
amphibians. If we could do further research and experiments on this topic, we could be able to
manipulate this field and learn more about gene expression and crossover frequency to have it
benefit our society.
References/Citations:
Meiosis and Genetic Diversity in the Model Organism, Sordaria. Written by Hass, C., Richter,
K., and Ward, A. 2014. Department of Biology, The Pennsylvania State University,
University Park, PA.
Cyr, R. 2002. Fungi I Evolution and Diversity, Phyla Chytridiomycota and Zygomycota. In,
Biology 110: Basic concepts and biodiversity
course website. Department of Biology, The Pennsylvania State University.
http://www.bio.psu.edu/
Engh, Ines, Minou Nowrousian, and Ulrich Kück. N.p., 2 July 2010. Web. 22 Oct. 2014.
http://www.sciencedirect.com/science/article/pii/S017193351000138X
Biology 110 Laboratory Manual 2014
