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Transcript

Cell Cycle, Mitosis, & Cancer

Lecture Goals:

  • Examine the steps of the cell cycle
  • Understand how cells divide and how that relates to growth
  • Examine the impacts of when the cell cycle is no longer regulated, resulting in cancer growth

Course Competencies: 16. Compare and contrast the biological processes of binary fission, mitosis and meiosis.(IX) 17. Describe the process of DNA replication and its relationship to cell division. (VII, IX)

Click the sound button for audio!

"Mitosis de cebolla" by arturoUPM is licensed under CC BY 2.0.

Presentation Links

Interphase

Mitotic Phase

Cell CycleOverview

Cancer: When the Cell Cycle Breaks

"lily mitosis" by kat m research is licensed under CC BY-SA 2.0.

Cell Cycle

Cell Replication and Division

The cell cycle is the process of a cell growing, performing required metabolic functions, replicating its DNA, and then dividing.

  • 2 major phases:
    • Interphase
    • Mitotic phase
    • Each major phase has its own subphases

Bio 2e Textbook Figure Figure 10.5

Cell Cycle

Cell Replication and Division

  • Interphase
    • Cell is growing and performing its function
    • Cells spend most of their time in interphase!
    • 3 subphases:
      • DNA synthesis and two different growth phases
  • Mitotic phase
    • Cell is actively dividing
    • 2 subphases:
      • Mitosis and cytokinesis

Bio 2e Textbook Figure Figure 10.5

Discussion Post #1

01:00

  • Define the cell cycle
  • What are the 2 main phases?
  • What are the subphases?

Submit for your discussion post!

Interphase

Cell Function and DNA Synthesis

  • Gap phase 1 (G1)
    • First growth phase
    • Little change is visible under a microscope
    • Cell accumulates material needed for DNA replication
      • DNA building blocks and proteins
  • Synthesis of DNA (S)
    • DNA is replicated
    • Results in duplicated chromosomes made from identical sister chromatids that are firmly attached at the centromere

Note: Throughout interphase, DNA remains in a semi-condensed chromatin form.

Bio 2e Textbook Figure Figure 10.5 "Interphase and Metaphase labeled on Onion Root Microscopic Image" by Natalierussell77 is licensed under CC BY-SA 4.0.

Recall: Nucleic Acids

Homologous Chromosomes vs Sister Chromatids

Chromatid

Chromatid

Chromatid - tightly bundled DNA (bundles together right before a cell divides)Chromosome - chromatid that contains unique genetic information

"Chromosome Terminology" by Christinelmiller is licensed under CC BY-SA 4.0.

Interphase

Cell Function, DNA Synthesis, and Growth

  • Gap phase 2 (G2)
    • Second growth phase
    • Cell prepares for dividing
      • Replenishes its energy stores
      • Grows larger to prepare to become two cells
      • Synthesizes proteins needed for moving chromosomes, such as tubulin
      • Organelles are duplicated
    • Just before mitosis, the cytoskeleton is dismantled (needed to help with division)

Another reminder - DNA remains in a semi-condensed chromatin form during interphase.

Bio 2e Textbook Figure Figure 10.5 "Interphase and Metaphase labeled on Onion Root Microscopic Image" by Natalierussell77 is licensed under CC BY-SA 4.0.

Discussion Post #2

03:00

  • Explain the difference between homologous chromosomes and sister chromatids
  • Briefly describe the three stages of interphase

Submit for your discussion post!

Mitosis (aka Karyokinesis)

The First Step of the Mitotic Phase

  • Mitosis is when the cell divides into two cells, called daughter cells.
  • 4 phases:
    • Prophase/prometaphase
    • Metaphase
    • Anaphase
    • Telophase

Bio 2e Textbook Figure Figure 3.31

Mitosis (aka Karyokinesis)

1.1 Prophase

  • Nuclear envelope breaks down
  • Membrane-bound organelles fragment and are moved to edge of cell
  • Mitotic spindles extend from the centrosomes
    • Spindles are made from microtubules (parts of the cytoskeleton)
  • Chromosomes begin to condense even more
    • Condense with the help of condensin proteins
    • Chromosomes are now visible under the microscope!

Bio 2e Textbook Figure Figure 3.31

Mitosis (aka Karyokinesis)

1.2 Prometaphase

  • Centrosomes move toward opposite ends of the cell
  • Chromosomes become even more condensed
  • Each sister chromatid develops a protein structure called a kinetochore
  • Mitotic spindles continue to develop
    • Some bind to the kinetochores
    • Others don't bind to the chromosomes
      • Called polar microtubules
      • Will be used to elongate the cell

Bio 2e Textbook Figure Figure 3.31

Mitosis (aka Karyokinesis)

2. Metaphase

  • Mitotic spindles line up the chromosomes at the metaphase plate (middle of the cell)
  • Each sister chromatid from one chromosome is attached to a spindle that came from opposite ends of the cell

Bio 2e Textbook Figure Figure 3.31

Mitosis (aka Karyokinesis)

3. Anaphase

  • Sister chromatids now separate to form daughter chromosomes
  • Daughter chromosomes are pulled to opposite sides of the cell by the mitotic spindles

Bio 2e Textbook Figure Figure 3.31

Mitosis (aka Karyokinesis)

4. Telophase

  • Chromosomes begin to decondense (unravel) back into the looser chromatin structure
  • Mitotic spindles break down into protein monomers called tubulin
    • Tubulin will be used to assemble the cytoskeleton in each daughter cell
  • Nuclear envelopes reform around the chromosomes

Bio 2e Textbook Figure Figure 3.31

Cytokinesis

The Last Step of the Mitotic Phase

  • Cell pinches inward, separating the cell into two daughter cells
  • Plant cytokinesis works slightly differently!
    • Cell plate forms between the two cells to separate them
    • Eventually becomes the cell wall

Bio 2e Textbook Figure Figure 3.31 https://www.savemyexams.com/a-level/biology/aqa/17/revision-notes/2-cell-structure/2-3-cell-division-in-eukaryotic--prokaryotic-cells/2-3-4-cytokinesis/

Mitotic Phase

Remembering Mitosis and Cytokinesis

  • Mitosis
    • Prophase/prometaphase - prep
    • Metaphase - middle
    • Anaphase - apart
    • Telophase - two new nuclei
  • Cytokinesis

Mitosis occurring in the root tip of an onionWhat is the correct order of these images?

View Answers

A

D

B

C

Bio 2e Textbook Figure Figure 10.5 https://vce.bioninja.com.au/unit-one/area-of-study-1-cell-develo/cell-cycle.html

A (prophase/prometaphase) D (metaphase) B (anaphase) C (telophase)

Mitosis and Cytokinesis

Visual of Cell Division

Discussion Post #3

03:00

  • What are the stages of mitosis and cytokinesis?
  • Briefly describe the major events that occur in each stage

Submit for your discussion post!

Cancer

Unregulated Cell Growth

  • Normally, cells contain checkpoints in the cell cycle to make sure they only divide when they need to
  • When the cell cycle is no longer controlled, cancer occurs and cells divide uncontrollably

Recommended Textbook Reading

OpenStax Biology 2e: Chapter 10

Not required, but highly recommended (it can be very helpful to see the material again but phrased a little differently!)