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The Effects of Radiation on Sordaria Fimocola

Kathleen Gruschow Samarth R. Biology 110 Lab Section 019 26 October 2017

Introduction The Evolution Canyon is a canyon in Israel that contains to very diverse slopes. The climate and the organisms both differ from the northern slope to the southern slope. The southern slope, also known as the African slope, is very dry with high temperatures. The northern slope, also known as the European slope, is humid with a lot of shade. This canyon is a good place to examine how environmental factors contribute to the evolution of organisms. Because of the differing factors, the southern slope has a higher crossover frequency than the northern slope. In one study, the southern slope was found to have a higher frequency of crossing over in locus-centromere intervals than the northern slope (Saleem p. 1). The higher crossover frequency causes more genetic diversity among those organisms. With the large number of genetic diversity, there are three different asci types evident. Within the three types of asci, there are recombinant and non-recombinant present. There are eight spores throughout the wild and tan asci, so variation occurs. The three possible variations for these asci are 4:4, 2:2:2:2, and 2:4:2. The first type, 4:4, is non-recombinant and experiences no crossing over. The order for this ascus is either four tans then four wilds, or vice versa. The other two types of asci both experience crossing over and they are both recombinant. The 2:2:2:2 asci are two tan spores, two wild spores, two tan spores, and then two wild spores or vice versa. The 2:4:2 asci occurs when the cross over produces two tan spores, four wild spores, and then two tan spores or vice versa. (Lab Manual p. 44). Image 1 shows the different types of asci from a microscopic view.

Image 1

4:4

2:2:2:2

2:4:2

There were two mating agar plates in the experiment. One mating agar plate was the control plate, and received no treatment. The second group of mating agar plates was the experimental group, it was exposed to radiation for two weeks. We observed the asci under the microscope at 400x. We counted the pattern of spores in the control and experimental groups and recorded the data. We calculated the frequency of each type of asci (A, B, and C) by using the equation: % of recombinant asci= (B+C) * (A+B+C). The percent crossover was calculated by the equation: frequency of recombinant asci *50. Radiation can cause harm to the DNA if it strikes the DNA directly. Radiation can cause a strand of the DNA to break, it could also alter the bases in DNA which ruins the sugars. Radiation can also cause damage to reproduction, if the damage is too strong it can kill the cell. If too many cells are killed, a vital organ may experience malfunctioning. Malfunctioning could potentially lead to the death of an organism. Severe atmosphere stresses such as radiation or temperature will lead to changes in recombination that will eventually result in an increase in genetic diversity as well as an increase in crossing over. My hypothesis for this experiment is that when the experimental group is exposed to radiation, it will have a higher cross over frequency than the control group who is not exposed to radiation. The experimental group will have a higher cross over frequency which means the experimental group will also have a higher genetic recombination rate among all of the Sordaria. Crosses were made between non-x-ray exposed wild type and x-ray exposed

tan type. Another cross that was examined was between non-x-ray exposed tan type and x-ray exposed wild type. There were control groups crosses that contained non-x-ray tan and wild type Sordaria. The independent variable in this experiment is the radiation from the x-ray. Without this independent variable, there would be no way of representing the differences in environments of Sordaria.

Materials and Methods The materials needed for this lab are mating agar plates, scalpels, surgical tape, marking pens, inoculating loops, pencils, microscope slides and coverslips, squirt bottles of water, disinfectant wipes, compound light microscopes, and Kim wipes and lens paper. To begin our lab, we sterilized all of our materials with a Clorox wipe to ensure that no outside organisms or materials could be detrimental to our results. There were two mating agar plates, one for the control group and one for the experimental group. A petri dish was set up by dividing the dish into four quadrants with drawn on black lines. The tan type and the wild type spores were organized in a way in which they were alternating each other, the same type sections were across from each other rather than directly next to each other. We then sealed the control and experimental dishes and let them sit for two weeks. (Lab Manual p.39). After two weeks, we broke the seal of the dishes and began the second part of the experiment. Using an inoculating loop, we scraped perithecia from the most heavily populated areas, the dividing lines, of the petri dish to get our sample. We placed a drop of water on a microscope slide, dropped the perithecia on top of the water, and then placed a cover slip on top. We then gently

Image 2

tapped the microscope slide with the eraser of a pencil in order to make the sample perethecia easier to examine. Image 2 shows how the four quadrants were split up into quadrants. The lighter and orangish quadrants are the tan type spores. The darker and greyish quadrants are the wild type spores. The divided lines appear black, because of the dense population of spores at those areas.

Results I was examining the agar control plate for my group. My individual findings were that there were more non-recombinant asci (4:4) than the two types of recombinant asci added together. Out of twenty total asci, eleven were non-recombinant. My small groups findings for the control were similar to my individual findings. Out of forty total asci, twenty-three were non-recombinant. The classes total findings for the control group was similar as well. Out of two hundred and thirty-one asci, one hundred and twenty-five were found to be nonrecombinant. This data shows that without receiving any treatment of radiation, the typical asci type is non-recombinant. The group and class data that I collected on the treatment groups showed a much higher number of recombinant asci rather than recombinant, proposing that radiation causes this increase in crossing over. These results agree with previous scientific experiments as well. The experimental group represents the southern slopes of Evolution Canyons, while the control group represents the northern slopes. In a study performed on the Evolution Canyons to detect color mutation, the mutation rates for the southern slopes were around five percent, while the northern slopes were only one point five percent (Lamb et al). These mutation rates are caused by genetic diversity in crossing over that are caused by radiation and surroundings, which was proven by our experiment.

Results of Amount of Asci Treatment

Non-recombinant Type A

Recombinant Type B 2:4:2

Recombinant Type C 2:2:2:2

Total Asci

WT H x T H

12

16

12

40

28

WT H x T L

18

32

30

80

62

WT L x T H

15

19

26

60

45

WT L x T L

6

8

7

21

15

WT L x T None

4

6

10

20

16

WT None x T None

125

59

47

231

106

Results of Cross-Over Frequencies Treatment Frequency of Recombinant Asci

Tota Recomb (B+

Frequency of Type B Asci (B/total)

Frequency of Type C Asci (C/total)

Ratio B/C

WT H x T H

70%

40%

30%

1.33

WT H x T L

77.5%

40%

37.5%

1.07

WT L x T H

75%

31.7%

43.3%

0.73

WT L x T L

71.4%

38.1%

33.3%

1.14

WT L x T None

80%

30%

50%

0.6

WT None x T None

45.9%

25.5%

20.4%

1.25

Discussion This experiment has shown that the increase of x-ray radiation on Sordaria causes an increase of recombination from the large number of crossovers in the experimental group. As radiation increased, the number of recombinant spores increased but the non-recombinant spores decreased. The results of this experiment were very closely related to my hypothesis, I was correct in my hypothesis that radiation would cause an increase in genetic diversity and crossing over. Because of the closeness of the sections results and the scientific explanation of this experiment, I believe there were very few errors in the procedure of the experiment. We were cautious and precise in every step of the experiment. This experiment relates to the Evolution Canyons because it shows how an organism can change to better adapt to its surroundings. To understand more on Evolution Canyons and the subject of this lab, we could change more environmental factors. Rather than solely using radiation, we could use factors such as temperature, air pressure, and sunlight as well. The most precise way to further this research would be to do a separate experiment for each of those factors rather than all together. By performing many different experiments with different factors, one could see exactly what affects the Sordaria and in what ways. In conclusion, radiation plays a huge role in the crossing over process of Sordaria. The more radiation that is present, the more crossing over will occur.

Wo r k sCi t e d Burpee, D., Cyr., Hass, C., Ward, A., and D. Woodward. A Laboratory Manual for Biology 110 Biology: Basic Concepts and Biodiversity. 2017. Department of Biology, The Pennsylvania State University, University Park, PA. Lamb, Bernard C, et al. “Inherited and Environmentally Induced Differences in Mutation Frequencies Between Wild Strains of Sordaria Fimicola From ‘Evolution Canyon.’” NCBI, PubMed, 1 May 1998, www.ncbi.nlm.nih.gov/pubmed/9584088. Saleem, M, et al. “Inherited Differences in Crossing over and Gene Conversion Frequencies between Wild Strains of Sordaria Fimicola from ‘Evolution Canyon’.” NCBI, PubMed, Dec. 2001, www.ncbi.nlm.nih.gov/pmc/articles/PMC1461899/. Figure 1: http://www.virofond.ulg.ac.be/Collectif/Image/Sordaria2.jpg Figure 2: http://hawaiireedlab.com/wpress/wp-content/uploads/2013/05/IMG_0054.jpg...