Mitosis Onion Root Tip Lab 3e1x3e

Mitosis Onion Root Tip Lab November 19, 2011 · 1 Comment · Uncategorized

Percentage of Cells in Each Mitosis Stage Question: How much time do cells spend in each part of the cell cycle? Hypotheses: If the tip of an onion root is magnified, then more than 90% of the cells will be in interphase. Constant: The microscope used to magnify the onion root tip, the slide the root is placed on stays the same, the day it’s magnified Procedure: 1. Obtain a slide of onion root cells. Examine the slide under the microscope using the low-power lens, then focus on high power. 2. Find examples of cells in each stage of the cell cycle, including interphase and the stages of mitosis. Draw and label 1 cell per stage in the provided table. Label structures the following structures: cell membrane, DNA/Chromosomes, Nuclear membrane, Nucleus on Table 1 of the handout (paper). 3. Select a random area of the slide to study using the high-power lens; focus on high power. 4. Identify the stage of each cell in the view, and record your data by using theOnion Root Tip Lab Data Table found here. 5. To make your counting faster…. 1. Find the total number of cells by counting the number of cells across (horizontally) and counting the number

of cells down (vertically). Multiply these numbers to find the total number of cells. 2. To find the number of cells in each stage of mitosis, count them (there won’t be that many). 3. To find the number of cells in interphase subtract the number of cells in the different stages of mitosis (prophase, metaphase, anaphase, telophase) from the total number of cells in the field of view. This will give you the number of cells in interphase. 6. Repeat steps 4 a second time for a second sample. 7. Calculate the percentage of cells in each part of the cell cycle for each sample. Complete Table 2. 1. Sample Calculation: (# of cells in interphase)/(total number of cells) x 100 = % of cells in interphase Backgound: The process by which a single cell divides into two identical “daugter” cells is called Mitosis. Each daughter cell has an identical number or chromosomes as the parent cell. Mitosis takes place in all living cells. The four stages of mitosis include prophase, metaphase, anaphase, and telophase. These stages follow each other without interruption. 1. What patterns exist in your data? In which stage of the cell cycle are most of the cells you examined? How does this data what you know about the cell cycle? Over 80% of the cells examined were in the stage of interphase. This proves information about the cell cycle to be correct by ing the fact that a vast majority of a cell’s life is spent in interphase.

2. Find the average percentage of cells in each stage of the cell cycle among the three samples. Assume that a cell takes 24 hours to complete one cell cycle. Calculate how much time is spent in each stage of the cell cycle. (Hint: Multiply the percentage of cells in each stage, as a decimal, by 24 hours). Sample Total Cells Interphase 1 11.00% 2 10.00% Average 0.105 Anaphase

Prophase

Metaphase

324

267

82.00%

19 5.00%

36

234

174

74.00%

22 9.00%

23

279

220.5 78%

20.5 0.07

29.5

Telophase

1 1.00% 1 1.00% 12 5.00% 3 1.00% 6.5 0.03 2 0.01 3. The cells in the root of an onion are actively dividing. How might the numbers you count here be different than if you had examined cells from a different part of the plant? The numbers could be different if examined from a different part of the plant because they might not be dividing as fast. More cells would be in interphase and hardly any examples of anaphase and telophase would be reported. 4. Using the data from Table 2, create a graph in Google Spreadsheets using the % of cells in each stage of

Mitosis. Add a title and label the graph. a picture of the graph to your post.

5. A chemical company is testing a new product that it believes will increase the growth rate of food plants. Suppose you are able to view the slides of a plant’s root tips that have been treated with the product. If the product is successful, how might the slides look different from the slides you viewed in this lab? The slides could look very different from the slides in this lab. The cells would divide much quicker in order for more rapid growth, therefore, there could be many more cells in the later stages of mitosis. The cells would be mostly in the stages of anaphase and telophase. 6. Design an experiment that would test the product described in question. Explain what you could test or do to show that the product really does increase the rate of cell growth and division in plants. Assume the product is a liquid that can be added to the soil in which the plant is growing. An experiment that could be conducted to prove that the liquid product increased the rate of cell growth would be… Before the liquid was applied, calculate the cells in each stage of mitosis, as well as interphase. After one week, the

cells would be examined again. Again, the number of cells in each stage of mitosis (and interphase) would be calculated. If the amount of cells in the later stages of mitosis increased rapidly over the week, it would most likely prove that the product aided in the plants fast growing. The hypothesis stated that 90% of the cells magnified from the cell root tip would be in interphase. The hypothesis was proven incorrect; the graph and data table both state that only 82% of the cells were proven to be in interphase. The average number of cells in anaphase and telophase were both less than 1%.The findings from this experiment confirm current explanations of the cell cycle by ing the fact that a vast majority of a cell’s life is spent in interphase. Information about the cell cycle have aided many scientists in discoveries about many things- from the creation of a person to cloning. An error that was made during this experiment was that the microscope wasn’t originally focused on the tip of the onion root. This would mess up the experiment results because the data wouldn’t be exclusively from the root tip. Another error that was made was that the number of cells in each stage of mitosis weren’t counted, they were more like estimated. This threw off percentages for each stage of mitosis and possibly is what made the hypothesis proven false. A modification that could be made to this experiment is magnifying root tips from multiple onions and finding the average. Also, the whole class could have shared their averages and a grand (and most accurate) average could be calculated.