Eukaryotic Cell Mitosis

I.CHROMOSOME DUPLICATION

1.Chromosomes are visible under a light microscope only when the cell is dividing 2.Chromatin- a combination of DNA and protein molecules

3.Before a cell divides the chromosomes are duplicated.

– When the cell divides, the chromatids separate. – Each new cell gets one chromatid. Cell division Micrograph

II.THE CELL CYCLE MULTIPLIES THE CELL

1.Cell Cycle- the series of events that takes place in a cell leading to its division & replication 2.During the cell cycle: – a cell grows – prepares for division 3.Divides to form two daughter cells, each of which begins the cycle again

4.The cell cycle consists of four phases: – G1 (First Gap Phase) – S Phase (Synthesis) – G2 (Second Gap Phase) – M Phase (Mitosis)

III.CELL DIVISION IS CONSTANT CHANGE

1.Interphase- the first stage of the cell cycle. During this phase the cell: – Grows – Makes new proteins & organelles – C’somes are replicated – DNA is made – Is the longest stage of the cell cycle 2.Interphase has 3 phases: G1, S, & G2

3.During G1, the cell: – increases in size – synthesizes new proteins and organelles

4.During the S phase: – chromosomes are replicated – DNA synthesis takes place – Once a cell enters the S phase, it usually completes the rest of the cell cycle

5.The G2 Phase (Second Gap Phase) – organelles & molecules required for cell division are produced – Once G2 is complete, the cell is ready to start the M phase— Mitosis

6.Mitosis has 4 phases: – Prophase – Metaphase – Anaphase – Telophase

7.Prophase The 1 st & longest phase of mitosis The centrioles separate & end up on opposite sides of the nucleus in an area called the centromere The centrosome helps organize the spindle Chromatin condenses into chromosomes. The centrioles separate and a spindle begins to form. The nuclear envelope breaks down. A cell in prophase of mitosis. (An epithelial cell in prophase of mitosis, treated with the anti-cancer drug taxol. Chromosomes are labeled blue. Taricha granulosa (newt) lung.) Observing Mitosis with Fluorescence Microscopy. Prophase. © by Michael W. Davidson and The Florida State University.

8.Metaphase 2 nd phase of mitosis – The chromosomes line up across the center of the cell – Microtubules connect the centromere of each chromosome to the poles of the spindle. Observing Mitosis with Fluorescence Microscopy. Metaphase. © by Michael W. Davidson and The Florida State University.

9.Anaphase – 3 rd phase of mitosis – the duplicated centromeres of each pair of sister chromatids separate – the now-daughter chromosomes begin moving toward opposite poles – The chromosomes continue to move until they have separated into two groups. Observing Mitosis with Fluorescence Microscopy. Anaphase. © by Michael W. Davidson and The Florida State University

10.Telophase – The last phase of mitosis – Chromosomes gather at opposite ends of the cell and lose their distinct shape – A new nuclear envelope forms around each cluster of chromosomes. Observing Mitosis with Fluorescence Microscopy. Telophase. © by Michael W. Davidson and The Florida State University.

11.Cytokinesis – the cytoplasm pinches in half. – Each daughter cell has an identical set of duplicate chromosomes. Actin (blue) and microtubules (orange) at the end of cytokinesis in a green urchin zygote. University of Washington Center for Cell Dynamics

IV.CYTOKENSIS DIFFERS IN PLANT & ANIMAL CELLS

1.Cytokinesis in Plant Cells – structure known as the cell plate forms midway between the divided nuclei – The cell plate gradually develops into a separating membrane. – A cell wall then begins to appear in the cell plate. Cell wall Cell plate

2.Cytokinesis in Animal Cells A cleavage furrow forms-An indention formed by microfilaments The pulling of the filaments separates the cytoplasm of the daughter cells

3.Timing of Cell Cycle 95% of the cell cycle is spent in interphase A typical rapidly dividing human cell with a total cycle time of 24 hours: – the G1 phase might last about 11 hours – S phase about 8 hours – G2 about 4 hours – and M about 1 hour.

Mitosis Video

V.ANCHORAGE 8.8

Discuss w/ partner: 1.Is there a difference in mitosis in animal cells that are suspended in a liquid versus attached to a solid surface. Explain *hint read page 135

Answer: Mitosis or cell division does not occur in animals cells that are suspended in liquid Scientist have discovered that animal cells only divide when they are attached to a solid surface. The cellular matrix provides the surface for these cells

1.Cells divide at different rates if they divide at all 2.Animal & plant cells only divide when they are in contact with a solid surface.

3.Anchorage Dependence- Keeps cells from dividing when they should not once cells become separated from their normal surroundings 4.Density- Dependent Inhibition- cells stop dividing when they touch one another

5.Growth Factor- A protein secreted by some body cells that stimulates the cells in the area to divide. – If the cells do not have enough of this protein they will not divide.

VI.GROWTH FACTORS

1.Cell Cycle Control System- proteins located in the cell that starts and coordinates the major events of the cell cycle.

2.A series of start, stop signals, and check points inside the cell keeps the cell cycle operating properly. 3.The start and stop signals are actually proteins.