Mitosis in Allium

Title: Mitosis in Onion Root Tips

Purpose: To determine the amount of time a cell spends in each phase of mitosis

Analysis Question:

1.  What does mitosis result in?

The process of mitosis leads to two daughter cells, each of which is identical to the original cell and diploid. In order to reach this state, DNA is replicated within the nucleus during Interphase. Mitosis is a normal process for cells, as it allow them to replace themselves as well as grow as an organism further. It is a process that occurs throughout the life span of an organism, not just at the beginning growth phases. This allows each daughter cell to have one of the identical sets of DNA, making it diploid and identical to the parent cell and the other daughter cell.

2.  What differences are their between mitosis in plants and animal?

There are slight differences between mitosis in plants and animals. In animals, spindle fibers gather around a centriole, which mitosis in plants doesn’t contain. In cytokinesis, animal cells pinch together to form two membranes. Because plants have cell walls, plants accommodate this by building a cell plate down the middle instead, which develops into a cell wall. Both the builing of the cell plate, which only plants have, and the centrioles, represent evolutionary differences in these different types of cells. Although there are differences, the essential parts of division are the same for both plants and animals.

3. Are centrosomes essential to mitosis?

The centrosome is necessary for mitosis because the spindle fibers are attached here. These split the sister chromatids apart, a process essential to mitosis. They are also responsible for aligning the chromosomes during metaphase, and they ensure that the DNA is split evenly between both new cells, and that each cell has all the DNA it needs. Without centrosomes that move towards opposite poles, the cell would be unable to split evenly and ensure there is DNA in both sides. Also, if centrosomes were not essential, they would have likely evolved out of cells.

Data Table:

Trial 1 Trial 2 Trial 3 Total Percentage (in %) Time in each phase (min)
Interphase 272 250 133 655 83.6% 1204.59
Prophase 32 20 40 92 11.74% 169
Metaphase 7 8 4 19 2.43% 34
Anaphase 4 2 2 8 1.02% 14.71
Telophase 4 4 1 9 1.15% 16.55
Total Cell 319 284 180 783 ———– ————-

Questions:

1. If the results had been restricted to the area of the root tip not actively dividing, would the results be different? What would they be?

If the results had not been restricted to the area of the root tip that is actively dividing, the results would be different. All the cells would appear to be in Interphase, without the other phases of division. When cells are not dividing, they perform regular cellular processes.  Because none of the cells in this sample would be in the process of dividing, no other phases (or far fewer) would be present in the sample.

2.   Based on the data found in Table 1, how much time does the cell spend in each phase of mitosis?

Based in the data found in the Table 1, it can be inferred that, within some margin of error the cell spends approximately 83.6% of it’s time in interphase, 11.7% of it’s time in prophase, 2.4% of it’s time in metaphase, 1.02% in anaphase, 1.15% in telophase. These results were expected, because it is known that a cell spends most of it’s time in Interphase, than Prophase. Telophase, Anaphase and Metaphase all were evenly distributed.

Although my results were what I expected, this lab may at times may be difficult to complete with accurate results. Because of the challenge in finding an excepted value for mitosis in onion root tips, it was hard to determine the accuracy of the data. Inaccuracy could be due to difficulties in differentiating between Prophase and Interphase of Mitosis in the onion root tip. Inaccuracy could have also arisen from choosing a sample to count that came from the wrong part of the root tip.

I enjoyed this Lab- we got a chance to explore Mitosis, to dream about how things grow and possibilities that division creates, and a chance  to examine the root tips of Onion Cells.

Mitosis in Onion Root Cells

Explore, Dream, Examine

-Serena

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