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CELL REPRODUCTION. THE CELL CYCLE AND MITOSIS. Lesson Objectives—Cell Cycle. Describe the properties of cell division in prokaryotes.

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Cell reproduction
CELL REPRODUCTION

THE CELL CYCLE

AND

MITOSIS


Lesson objectives cell cycle
Lesson Objectives—Cell Cycle

  • Describe the properties of cell division in prokaryotes.

  • Describe cell division in eukaryotes. Explain the main differences between cell division in prokaryotic and eukaryotic cells.

  • Describe the basic properties of chromosomes.

  • Describe the key steps in the cell cycle.

  • Identify and describe the main processes in mitosis.

  • Describe how the cell cycle is controlled and define cancer.


Cell reproduction1
CELL REPRODUCTION

  • Cell Division: process by which a cell divides to form two new cells (daughter cells)

  • Three types of cell division, or cell reproduction

    • Prokaryotes (bacteria)

      • Binary fission divides forming two new identical cells

    • Eukaryotes

      • Mitosis

        • Cell or organism growth

        • Replacement or repair of damaged cells

      • Meiosis

        • formation of sex cells, or gametes


Why do cells divide
Why do cells divide?

1: DNA Overload

  • If cells grow without limit, an “information crisis” would develop

  • DNA cannot serve the needs of the increasing size of cell

    2: Exchange of materials

  • Food and oxygen have to cross membrane very quickly

  • Waste must get out

  • If cell is too large, this occurs too slowly and cell will die


Prokaryotic cell division
PROKARYOTIC CELL DIVISION

  • Binary fission

    • 3 main steps:

      1: DNA Replication—DNA is copied, resulting in 2

      identical chromosomes

      2: Chromosome Segregation—2 chromosomes separate,

      move towards ends (poles) of cell

      3: Cytokinesis—cytoplasm divides, forming 2 cells

    • Each new daughter cell is

      genetically identical to parent cell


The cell cycle
THE CELL CYCLE

G1 phase

M phase

S phase

G2 phase


Cell cycle interphase
CELL CYCLE-INTERPHASE

  • Interphase: period of growth and DNA replication between cell divisions

  • Three phases:

    • G1 Phase

      • cell increases in size

    • S Phase

      • Replication of chromosomes

        • Now two strands called sister chromatids joined by a centromere

    • G2 Phase

      • organelles double

      • new cytoplasm forms

      • All other structures needed for mitosis form


Cell reproduction


Eukaryotic cell division
EUKARYOTIC CELL DIVISION

  • DNA found on chromosomes located in nucleus of cell

  • Cell cycle continuous process

    • Cells grow

    • DNA replicated

    • Organelles duplicated

    • Divide to form daughter cells

    • 2 Main steps:

      1: Mitosis (4 steps—Prophase, Metaphase, Anaphase, Telophase)

      Nucleus divides

      2: Cytokinesis—Cytoplasm divide, forming 2 cells

      Each new daughter cell is genetically identical to parent cell


Cell reproduction

  • Mitosis = nuclear division

  • Mitosis is followed by cytokinesis (cell division)

  • The steps of mitosis ensure that each new cell has the exact same number of chromosomes as the original


Mitosis
MITOSIS

  • Process that divides cell nucleus to produce two new nuclei each with a complete set of chromosomes

  • Continuous process

  • Four phases (PMAT)

    • Prophase

    • Metaphase

    • Anaphase

    • Telophase


Cell reproduction

  • (1)Prophase

  • (2)Metaphase

  • (3)Anaphase

  • (4)Telophase

  • PMAT

Interphase

1

2

4

3

Cytokinesis


Cell reproduction

1. chromosomes visible (sister chromatids)

2. centrioles migrate to the poles (only in animals)

3. nuclear membrane disappears

4. spindle forms


Cell reproduction

Equator


Cell reproduction


Cell reproduction

1. chromosomes uncoil • now chromatin

2. nuclear membranes reform

3. spindle disappears


Cell reproduction

  • Occurs at end of Mitosis

    --division of the cytoplasm to form 2 new daughter cells

    --organelles are divided

    -Daughter cells are genetically identical

Cells return to interphase


Cell reproduction

Mitosis

  • Name the phases starting at the top.


Cell reproduction

2.Name the phase

3.Identify X

4.Identify Y


Cell reproduction

5. Name the phase


Cell reproduction

6. Name the phase


Control of the cell cycle
Control of the Cell Cycle

  • Regulatory proteins called cyclins control the cell cycle at checkpoints:

  • G1 Checkpoint—decides whether or not cell will divide

  • S Checkpoint—determines if DNA has been properly replicated

  • Mitotic Spindle Checkpoint—ensures chromosomes are aligned at mitotic plate



Cancer cells
CANCER CELLS

  • Result of uncontrolled cell division of cells that have lost ability to regulate cell cycle

  • Reproduce more rapidly than normal cells

  • Masses formed called ‘tumors’


Lesson summary cell cycle
Lesson Summary—Cell Cycle

  • The cell cycle is a repeating series of events, characterizing the life of a eukaryotic cell.

  • Binary fission is a form of cell division in prokaryotic organisms that produces identical

    offspring.

  • As a eukaryotic cell prepares to divide, the DNA and associated proteins coil into a

    structure, known as a chromosome.

  • The DNA copies during the S phase of the cell cycle, resulting in a chromosome that

    consists of two identical chromatids, known as sister chromatids, attached at a region

    called the centromere.

  • Any cell containing two sets of chromosomes is said to be diploid; the zygote forms

    from the fusion of two haploid gametes.

  • The cell cycle has five phases: the first growth (G1) phase, the synthesis (S) phase,

    the second growth (G2) phase, mitosis, and cytokinesis.

  • Mitosis is the division of the nucleus; four distinct phases of mitosis have been

    recognized: prophase, metaphase, anaphase, and telophase.

  • Cytokinesis is the division of the cytoplasm.

  • The cell cycle is controlled through feedback mechanisms.

  • Cancer results from uncontrolled cell division, due to the loss of regulation of the cell

    cycle.