Observing Mitosis and Meiosis on Cell Specimens
Name: Low Celine
Tables of Content…………………………………………………………………………….ii List of Illustrations…………………………………………………………………………… iii Synopsis………………………………………………………………………………………. iv 1. Objectives of Experiment………………………………………………………………… 1 2. Introduction……………………………………………………………………………….1 3. Theory…………………………………………………………………………………….. 2 4. Procedures………………………………………………………………………………... 3 5.1 Preparation of Onion Root Tip………………………………………………………… 3 5.2 Observation of prepared slides: Mitosis in Onion root tip & Whitefish Blastula……... 3 5. Results and Calculation……………………………………………………………………. 4 6. Discussion………………………………………………………………………………….. 7
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Lastly, cytokinesis which is the splitting of the daughter cells furrow will be formed and the cell will pinched into two. Meiosis According to the Biology-Online Organization (2006), Meiosis contained two type of phases meiosis I and meiosis II. In the prophase I, homologous chromosomes in the nucleus begin to pair up with one another and then split into chromatids where crossing over can occur. For metaphase I, the chromosomes will align at the equator of the cell. The bivalents are aligned randomly increasing the genetic variation via independent assortment. In the anaphase 1, the homologous chromosomes move to opposing poles from the equator. A new nuclei will be formed around each pole alongside each new chromosomes compliment in the telophase I. For prophase II, the second meiotic division will be initiated and the nuclear membrane will disappear. In the metaphase II, the pair of chromatids will be lined up at the equator. For the anaphase II, via the spindle fibers, each of these chromatids will be moved away from the equator to the poles. Lastly, in the telophase II the four new haploid gametes are created which will thus fuse with the gametes of the opposite sex to form a zygote. 4. Procedures: 4.1 Preparation of onion root tip slide Firstly, the onion root tip was obtained. The first one to three millimeter of the root tip was cut off using scalpel. With the use of
Chromosome pairs line up across the equator of the spindle at metaphase I (5). In anaphase I the chromosomes separate and travel to opposite ends of the spindle. The chromosomes migrate to the equators of two new spindles for metaphase 2 (7). Next the chromatids are pulled apart in anaphase 2 to form four clusters of chromosomes in telophase 2. The nuclear envelopes reform around four haploid nuclei that will give rise gamete
a) As before follow instructions in the handout and draw pictures for each stage of Meiosis I an Meiosis II – color!
Meiosis consists of one DNA replication and two nuclear divisions resulting in 4 daughter cells. The process which provides for genetic variation is crossing over. Crossing over occurs in the early stages when homologous chromosomes move together so that their chromatids form a tetrad. This is called synapsis and allows for the exchange of chromosome sections.
Interphase: This particular stage is divided into three phases, G1 (first gap), S (synthesis), and G2 (second gap). During all three phases, the cell grows by producing proteins and other organelles within the cytoplasm. However, chromosomes are replicated only during the S phase. In all, a cell grows (G1), continues to grow as it duplicates its
These bivalents line up along the equator during metaphase I, the arrangement of the bivalent is completely random and relative to the orientation of the other bivalents, this is known as the independent assortment of chromosomes. This is followed by anaphase I where the homologous chromosomes separate and move to the opposite poles of the cell. At telophase I the cell divides into two, each cell contains one chromosome from each homologous pair. The second stage of meiosis is similar to mitosis.
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
Without cell division and the cell cycle nearly all life would fail to exist. Cell division allows an organism to not only replace its own cells but to create offspring. The cell cycle consists of two main parts: interphase and mitotic phase. Within these two phases the processes can be broken down into further categories. Interphase can be broken down into three subphases that are the necessary preparations the cell makes in order to be ready to divide during mitosis. For this lab we looked mainly at the mitotic phase because of its fascinating and rapid changes to the cell. The cell types we looked at were prepared slides of whitefish and 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
Response Feedback: Meiosis occurs only in replicating gametes or reproducing cells. In phase one, the number of chromosomes is reduced by half but the chromatid pairs remain together. In phase two, the chromatids split apart forming four daughter cells. Non-germ cells such as red blood cells or skin cells undergo mitosis.For more information on this topic, consult:Carol Mattson Porth and Glen Matfin, Pathophysiology, 8th Edition,
The observation under the microscope of a cell of an onion skin soaked for 15 minutes in distilled water showed that the cell membrane was pressed against the cell wall. The cell
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.
Once the hydrochloric acid had been rinsed away from the onion root I placed it on a microscope slide and used the spatula to macerate (break up) the root tip until it