The Effect Of Temperature On The Duration Of Mitotic Stages During The Onion Root Tip Squashes

Exercise 3A is a study of mitosis. You will simulate the stages of mitosis by using chromosome models.You will use prepared slides of onion root tips to study plant mitosis and to calculate the relative duration of the phases of mitosis in the meristem of root tissue. Prepared slides of the whitefish blastula will be used to study mitosis in animal cells and to compare animal mitosis and plant mitosis.

In this experiment first the stages of an onion cell undergoing mitosis are going to be observed and every stage is going to be detected and drawn on paper. A brief description to what is going on should be attached to the pictures. This is important to understand the basics of cell division which is necessary growth,repair and asexual reproduction. Second the number of cells undergoing each phase is going to be counted to figure out in which phase the cell remains the most. If interphase is the stage in which the cell grows and prepares for cell division then the

In the onion root tip, regions other than the apical (or at top of) meristem contain cells that are not actively dividing. These cells are in interphase. In this case, they would represent the majority because cells spend most of their time in interphase anyway. They are elongating, differentiating, and performing their functions for the organism. Mitotic stages would not have been found in these areas.

Mitosis and meiosis are similar in several ways and different in others. The similarities include that both processes involve IPMAT. IPMAT is interphase, prophase, metaphase, anaphase and telophase. The parent cells are diploid. They both end with cytokinesis. In Metaphase and Metaphase II, the sister chromatids line up along the center. Then in Anaphase and Anaphase II, these chromatids are split and pulled towards the centrosomes. The differences are that mitosis consists of 1 division while meiosis consists of 2. Four genetically different, haploid sex cells are the products of meiosis and 2 identical, diploid somatic cells from mitosis. Mitosis occurs in all organisms except viruses and meiosis only occurs in plants, animals, and fungi.

A) Meiosis consists of two cell divisions and is broken up into Meiosis I and Meiosis II. At the beginning of the Cell Cycle, in this case there are four chromatids each from the homologous pairs being A, a, B, b. This is the Diploid number (4) meaning it is 2 times the haploid number that will be seen at the end of meiosis II. During the S phase of interphase, the chromatids replicate and reach the end of G2 phase. Now starting meiosis, during the first stage of prophase I the chromosomes condense and pair up through synapsis with their sister chromatids creating AA, aa, BB, bb. After they pair up they go through a process called crossing over, where the homologous chromosomes share a piece of their genetic material with each other. Crossing over allows for the genetic diversity of chromosomes. Now there are four homologous chromosomes Aa, Aa, Bb, Bb, each containing heterozygous alleles because the sister chromatids exchanged genetic information with their homologous pair. During late prophase I, spindle fibers being to form where they will later attach to a homologous chromosomes centromere. The next stage is Metaphase I. During metaphase I, the homologous pairs line up at the metaphase plate, also known to be the center of the cell. The homologous pairs form a tetrad which is considered a group of four homologous chromosomes. These homologous chromosomes orient themselves randomly, which is know as the process of independent

Although mitosis is just a fraction of time compared to interphase it can be divided into four distinct subphases. If we start viewing a cell under a brightfield microscope right at the end of interphase subphase G2 we would see that throughout the interphase process (fig 1) the cell has grown considerably in size due to production of extra mitochondria and endoplasmic reticulum. The cell has also gone through the labor of duplicating all of its chromosomes, a process known as DNA synthesis. Now that the cell has made all of these preparations it's time to start prophase (fig 2), the first stage of the mitotic phase. This stage is visibly identified by the chromatin becoming the tightly formed chromosomes. During the lab we were able to view these newly formed chromosomes best on the onion root tip

_____ In swine, when a pure-breeding red is crossed with a pure-breeding white the F1 are all red. However, the F2 shows 9 red, 1 white and 6 of a new color, sandy. The Sandy phenotype is most likely determined by

The cell cycle is a series of stages that occurs when a new cells makes the division from the parent cell to two daughter cells. This is a stage in cellular reproduction. The cell cycle consists of three phases, interphase, mitosis, and cytokinesis. During Interphase, a cell will continue to perform its functions as usual. The time frame for Interphase varies; while an embryonic cell will take just a few hours to complete the cycle, a stem cell from an adult can take 24 hours (Mader, Windelspecht, 2015). After the interphase stage completes itself, a complete nuclear division happens and mitosis occurs. During the stage of mitosis, the daughter cells will receive the same amounts of the contents of the parent cell. Throughout the last stage, in the cytoplasm there is a division known as Cytokinesis (Mader, Windelspecht, 2015). Cytokinesis occurs differently in plant cells than it does in animal cells, as the cell wall around the plant prevents the process from happening the same way. Instead, a new plasma membrane and cell walls are built are built between the daughter cells. However, in animal cells a single cell will become two (Mader, Windelspecht, 2015).

3. Switch to high power and center your slide in the apical meristem region, so that you have a field of view in which there is a wide selection of cells in various stages of mitosis (including interphase). Be sure to adjust your light for optimum viewing. Refer to Figure 3A, 3B, 3C: Stages of mitosis in onion root tip cells for guidance.

To observe mitosis in onion root tip cells and record the different phases of mitosis.

There are four stages of mitosis. The first stage is the prophase. In this stage the chromosomes become

Staining the cells with dye allows us to visualize the structures of the cell more precisely under a microscope.

E.G Lignowski and E.G Scott, authors of the journal Weed Science Society of America, both experimented on the effect of the herbicide trifluralin. Their goal for this experiment was to “study the mitotic inhibition produced by trifluralin in more detail to determine if this herbicide was acting as a metaphase inhibitor” (Lignowski 267). Essentially, their hypothesis was right. However the steps had to be taken, it was previously known that trifluralin does have an effect on mitosis, Lignowski and Scott hoped to seek the mitotic phase in which trifluralin inhibits. The materials used for this lab experiment were “methanol (0.05%), polyoxyethylene

Making the onion tip root cell slide was successful. Our results supported the hypothesis because we saw cells in the onion root tip in prophase, metaphase, and anaphase. As we went up in power objectives, each phase of the cell became more definitive. The cell root was a great indicator of the structures of the different cycles of the cell. This is important because we will be prepared for future labs working with the microscopes and can now adjust it for the best view of the slide. We practiced working with the compound light microscopes and different phases of the cell cycle. Onion root tips are useful to observe mitosis because the cells are frequently diving as the root grows. So when we stained the cell, we caught many cells in different phases. The significance of this lab was to better understand the process and stages of mitosis and meiosis and compare and contrast the mitotic process in plants and animals. We grasped the concepts of what the chromosomes look like, and what they look like in each step of the processes. Having read much about mitosis and meiosis, seeing these cells was the real application of describing and understanding the stages.

The main focus of this lab was to be able to understand the different phases of mitosis and the cell cycle and also identify what those stages may look like. Mitosis is the process in which concerns the production of new cells. For example, when apoptosis(cell death) the process of Mitosis begins to replace the dead cells. To be able to familiarize ourselves with this concept, we took a sample of an onion root and had it put through a process to be able to look at the different phases under the microscope. We found that the majority of the cells were mostly undergoing Interphase or Prophase which are the phases in charge of crossing over of DNA and where the chromosomes then become visible and the nuclear envelope dissipates. The conclusion of this lab was that Mitosis is essential for the production of new cells. In the case of the onion root sample, the cells were damaged leading to the tester to undergo Mitotic cell division and it was found that mainly Interphase and Prophase were the stages that occurred in this lab.