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The Cell Cycle and Mitosis
From https://openlab.citytech.cuny.edu/bio-oer/cell-division/. Edited by Rosana Zenil-Ferguson (08-23-2019)
Introduction: The Cell Cycle and Mitosis
The cell cycle refers to a series of events that describe the metabolic processes of growth and replication of cells. The bulk of the cell cycle is spent in the “living phase”, known as interphase. As you read previously, the interphase has 3 distinct phases: G1 (Gap 1), S (Synthesis) and G2 (Gap 2),
Interphase is further broken down into 3 distinct phases: G1 (Gap 1), S (Synthesis) and G2 (Gap 2). G1 is the phase of growth when the cell is accumulating resources to live and grow. After attaining a certain size and having amassed enough raw materials, a checkpoint is reached where the cell uses biochemical markers to decide if the next phase should be entered. If the cell is in an environment with enough nutrients in the environment, enough space and having reached the appropriate size, the cell will enter the S phase. S phase is when metabolism is shifted towards the replication (or synthesis) of the genetic material. During S phase, the amount of DNA in the nucleus is doubled and copied exactly in preparation to divide. The chromosomes at the end of G1 consist of a single chromatid. At the end of S phase, each chromosome consists of two identical sister chromatids joined at the centromere. When the DNA synthesis is complete, the cell continues on to the second growth phase called G2. Another checkpoint takes place at the end of G2 to ensure the fidelity of the replicated DNA and to re-establish the success of the cell’s capacity to divide in the environment. If conditions are favorable, the cell continues on to mitosis.
Mitosis is the process of nuclear division used in conjunction with cytokinesis to produce 2 identical daughter cells. Cytokinesis is the actual separation of these two cells enclosed in their own cellular membranes. Unicellular organisms utilize this process of division in order to reproduce asexually. Prokaryotic organisms lack a nucleus, therefore they undergo a different process called binary fission. Multicellular eukaryotes undergo mitosis for repairing tissue and for growth. The process of mitosis is only a short period of the lifespan of cells. Mitosis is traditionally divided into four stages: prophase, metaphase, anaphase, and telophase. The actual events of mitosis are not discreet but occur in a continuous sequence—separation of mitosis into four stages is merely convenient for our discussion and organization. During these stages, important cellular structures are synthesized and perform the mechanics of mitosis. For example, in animal cells, two microtubule-organizing centers called centrioles replicate. The pairs of centrioles move apart and form an axis of proteinaceous microtubules between them called spindle fibers. These spindle fibers act as motors that pull at the centromeres of chromosomes and separate the sister chromatids into newly recognized chromosomes. The spindles also push against each other to stretch the cell in preparation of forming two new nuclei and separate cells. In animal cells, a contractile ring of actin fibers cinches together around the midline of the cell to coordinate cytokinesis. This cinching of the cell membrane creates a structure called the cleavage furrow. Eventually, the cinching of the membrane completely separates into two daughter cells. Plant cells require the production of new cell wall material between daughter cells. Instead of a cleavage furrow, the two cells are separated by a series of vesicles derived from the Golgi. These vesicles fuse together along the midline and simultaneously secrete cellulose into the space between two cells. This series of vesicles is called the cell plate.
Figure 1: The four stages of mitosis. Prophase (sometimes also subdivided in Prometaphase), Metaphase, Anaphase, and Telophase. The goal of mitosis is to create two cells with the same amount of DNA than the original cell.
The four stages of mitosis in figures.
4. Telophase and Cytokinessis
Learn About Cell Division And Mitosis Yeast | Chegg.com – Commonly known as equal division, mitosis is a type of cell division during which the parent cell splits into two equal daughter cells which are similar to parent cells having the same number and kind of chromosomes. Mitosis is a common mode of cell division for growth in all organisms and unicellular organisms such as yeast.For unicellular organisms, cell division is the only method to produce new individuals. In both prokaryotic and eukaryotic cells, the outcome of cell reproduction is a pair of daughter cells that are genetically identical to the parent cell. In unicellular organisms, daughter cells are individuals.produce new organisms Multi cellular organisms undergo mitotic cell division to increase the size of the organism Cells that do not receive the correct signals to move from G1 into S phase will enter G0 and therefore will
Prokaryotic Cell Division – Introductory Biology – Compare and contrast the role of cell division in unicellular and multicellular organisms. Prokaryotes reproduce by binary fission; multicellular organisms undergo mitosis. Genome. The total amount of genetic information in the chromosomes of an organism, including its genes and DNA sequences. The genome of eukaryotes is made up of a singleMitosis is the process of nuclear division used in conjunction with cytokinesis to produce 2 identical daughter cells. Cytokinesis is the actual separation of these two cells enclosed in their own cellular membranes. Unicellular organisms utilize this process of division in order to reproduce asexually. Prokaryotic organisms lack a nucleus, therefore they undergo a different process calledAsexual Reproduction Remember that asexual reproduction results in offspring that are clones and does not involve the union of sex cells. The following information is mostly notes interspersed with a few questions. You will submit this for your assignment today. Asexual reproduction in unicellular organisms Protists (eukaryotic): Mitotic cell division results in two identical organisms Mitotic
Biology Flashcards | Quizlet – In unicellular organisms, division of one cell reproduces the entire organism. Multicellular organisms depend on cell division for: Development from a fertilized cell Growth Repair Cell division is an integral part of the cell cycle, the life of a cell from formation to its own division. Most cell division results in identical daughter cellsFor unicellular organisms, cell division is the only method used to produce new individuals. In both prokaryotic and eukaryotic cells, the outcome of cell reproduction is a pair of daughter cells that are genetically identical to the parent cell. Mitotic Spindle Apparatus. on the other hand, do not undergo karyokinesis and, thereforeYes. Ciliates such as Paramecium are very well known for their sexual reproduction, in which two cells come together and exchange haploid micronuclei (with their cargo of DNA). This is called conjugation. It results in cells that are not genetical…