Review M1&2

Cards (28)

  • No part of this lecture may be reproduced, in any form or by any means, without permission in writing by the Biology 1A03 professor Dr. Lovaye Kajiura
  • Copying Biology 1A03 lecture materials for distribution, for example uploading materials to a commercial website, is strictly prohibited
  • Copyright 2024 © L. Kajiura, McMaster University, Biology 1A03
  • We will begin by giving honour and thanks to the Haudenosaunee and Anishanaabe nations as the traditional inhabitants of the lands where McMaster stands
  • To say that is to acknowledge a debt to those who were here before us and to recognize our responsibility, as guests, to respect and honour the intimate relationship Indigenous peoples have to this land
  • Mitosis
    Eukaryotic cells reproduce by this process, producing daughter cells that are genetically identical to the parent cell
  • Functions of mitotic cell division
    • Growth
    • Development
    • Repair
  • Cell cycle
    Has 4 phases: G1, S, G2, M
  • G1 phase

    Cell growth & duplication of organelles
  • S phase

    DNA synthesis (chromosomes are replicated)
  • G2 phase

    Cell growth & duplication of organelles to build the protein "machinery"
  • Gap phases

    Ensure the parent cell is large enough in size & has the required organelles before mitosis occurs, so the daughter cells will function normally
  • Phases of mitosis
    1. Prophase
    2. Prometaphase
    3. Metaphase
    4. Anaphase
    5. Telophase
    6. Cytokinesis
  • Prophase
    • Chromatin fibers contract (DNA condenses) by tightly coiling
    • Chromosomes are visible & each consists of two identical sister chromatids joined together at the centromere
    • Mitotic spindle forms
    • Assembly of microtubules begins in the centrosome (animals) and the microtubule organizing centre (plants)
    • In animals, the centrioles begin to move apart to opposite sides of nucleus (2 poles)
  • Prometaphase
    • Chromosomes do not appear completely aligned or organized
    • Spindle fibers attach to sister chromatids at the kinetochore regions
  • Metaphase
    • Chromosomes line up along the Metaphase Plate
    • Centromeres are aligned on the metaphase plate, which is located equidistance from the two poles
  • Anaphase
    • Binding proteins between the sister chromatids break down
    • Centromeres of sister chromatids disjoin & segregate, this process is called Disjunctional Segregation
    • Chromosomes move centromere first (they appear V shaped)
    • Cell elongates
  • Telophase
    • Nonkinetochore microtubules further elongate the cell
    • Two daughter nuclei form
    • Formation of the nuclear envelopes around each set of chromosomes
  • Cytokinesis
    • In animals, slime molds, & fungi, a cleavage furrow forms
    • In plants, a cell plate forms
  • The 2001 Nobel Prize in Physiology & Medicine was jointly awarded for discoveries of the key regulators of the cell cycle
  • Cyclins
    Proteins that oscillate in concentration during the cell cycle and control cyclin dependent kinase (CDK) activity
  • CDK (Cyclin Dependent Kinase)

    Protein kinase that uses ATP to add phosphate groups to proteins, inducing conformational changes, and must be attached to cyclin to be active
  • Cell cycle checkpoints
    • Molecular mechanisms that regulate the cell cycle
  • Origins of replication (ori sites)
    Specific points where DNA replication begins, where the DNA double helix opens up to form 2 single strands and replication forks spread in both directions
  • Leading strand
    Continuous synthesis, grows in 5' to 3' direction, new nucleotides added only to 3' end
  • Lagging strand
    Discontinuous synthesis, grows in overall direction of 3' to 5' direction, produced by Okazaki fragments that individually grow in 5' to 3' direction
  • Ligase
    Catalyzes the formation of phosphodiester bonds joining the new Okazaki fragments in the growing lagging strand
  • The Meselson Stahl experiment supported the semiconservative DNA replication model