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5.1 The Cell Cycle

KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

5.1 The Cell Cycle

!  Cell Cycle Definition •  Regular pattern of growth, DNA replication, and

cell division that occurs in eukaryotic cells. Pg 134

•  End 1 cell division to the end of the next •  Occurs every 24 hours, but varies from cell to

cell

5.1 The Cell Cycle

!  Cell Cycle (Eukaryotic) 1.  Growth

2.  DNA Replication

3.  Cell Division

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5.1 The Cell Cycle

!  Eukaryotic Cells •  EU = True (True Nucleus) •  Membrane-bound Organelles •  Complex •  Unicellular/Multicellular •  Animals/Plants •  Mitosis

5.1 The Cell Cycle

5.1 The Cell Cycle

!  4 Main Stages of Cell Cycle 1.  Gap 1(G1)

2.  Synthesis (S)

3.  Gap 2 (G2)

4.  Mitosis (M)

Interphase

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5.1 The Cell Cycle

•  Longest •  “Preparation” phase •  Carry out normal Functions •  Before the cell enters cell

division •  Get nutrients, genetic

material together

Interphase

•  Gap 1 (G1) •  Synthesis (S) •  Gap 2 (G2)

3 Stages

5.1 The Cell Cycle

Interphase�

5.1 The Cell Cycle

GAP 1 • Cells perform normal functions

• Increase in size

• Organelles increase in number

• Cells spend most of its time

Checkpoints  Nutrition

 Adequate size

 Undamaged DNA

 Cell division signals

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5.1 The Cell Cycle

!  Synthesis (S)

•  To make, combining parts

•  DNA replication

•  2 Sets of DNA

5.1 The Cell Cycle

!  Gap 2 (G2) •  Prepare for mitosis •  Check for ERRORS in

chomosomes •  Prevent mutations with p53

(protein “Guardian of genome”)

•  If defect in p53 = CANCER

5.1 The Cell Cycle

!  Mitosis (M) 2 Steps 1. Mitosis 2. Cytokinesis

• Shortest • Mitosis = divides in nucleus • Cytokinesis = divides cytoplasm • Controlled by proteins

• Nuclear Membrane dissolves • DNA condenses • Separates • Form 2 “new” nuclei

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5.1 The Cell Cycle

5.1 The Cell Cycle

!  Cells divide at different rates.

•  The rate of cell division varies with the need for those types of cells.

•  Some cells are unlikely to divide (G0).

5.1 The Cell Cycle

!  Cell Division Rates

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5.1 The Cell Cycle

!  G0 •  Cells don’t divide or stop •  Continue and live forever

G0

5.1 The Cell Cycle

!  Cell size is limited.

•  Volume increases faster than surface area.

5.1 The Cell Cycle

•  Surface area must allow for adequate exchange of materials.

–  Cell growth is coordinated with division.

–  Cells that must be large have unique shapes.

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5.1 The Cell Cycle

!  Questions

1.  What may happen if the G2 checkpoint stopped working?

2.  What are the 4 main stages of the cell cycle?

3.  What can you infer about the amount of time a cell spends in each stage?

5.1 The Cell Cycle

•  The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis.

–  Gap 1 (G1): cell growth and normal functions

•  Mitosis occurs only if the cell is large enough and the DNA undamaged.

–  DNA synthesis (S): copies DNA

–  Gap 2 (G2): additional growth

–  Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)