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Cell Cycle and Mitosis. Objectives: - to describe the phases on mitosis - to compare the differences between cell division in plant cells and animal cells - to analyze the link between mitosis and cancer. Reasons Why a Cell Would Divide. To repair or heal damaged tissue - PowerPoint PPT Presentation
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CELL CYCLE AND MITOSISObjectives:
- to describe the phases on mitosis - to compare the differences between cell division in plant cells and animal cells - to analyze the link between mitosis and cancer
Reasons Why a Cell Would Divide
To repair or heal damaged tissue For multicellular organisms to grow To keep cell sizes small for increased efficiency For reproduction in unicellular organisms
Activity
Brainstorm in at your tables what is needed for a cell to divide.
Reading Assignment
Read Section 10-1, p.241-243 titled Cell Growth. Table 1 – Describe to the class “DNA Overload” Table 2 – Describe to the class “ Exchanging
Materials” Table 3 – Describe to the class “Ratio of Surface
Area to Volume” Table 4 - Describe to the class “Division of the
cell” Complete Worksheet 10-1 “Cell Growth”
Activity
Using your biological intellect, put these slides in order from first to last. Analyze each of the slides and on the slide list what actions you think are taking place.
Put the Slides in Order
The Correct Sequence is …
1 2 3
4 5
The Stages of Cell Cycle
The actual division of the cell is broken into 2 stages Mitosis is the division of the cell nucleus Cytokinesis is the division of the cytoplasm
In reality the cell cycle is much more complex and is broken into four phases
The Stages of the Cell Cycle
Interphase includes: G1 Phase S Phase G2 Phase
M PhaseMitosis
Prophase Metaphase Anaphase Telophase
Cytokinesis
The Stages of Cell Division
Cell Division Video
G1 Phase
Cells increase in size Synthesis of new proteins and organelles
S Phase
Chromosomes replicate and the synthesis of DNA molecules takes place.
DNA Replication Helicase “unzips” the double helix by breaking the
hydrogen bonds between the nitrogen bases. Each single strand of the DNA acts as a template. DNA polymerase allows free floating nucleotides to
bond to the single strand of DNA to create two daughter molecules.
S Phase
Activity
Draw a DNA triplet with the base sequence ATG on the left side. Make the 5’ the top left.
G2 Phase
Centrioles replicate The proteins required for cell division are
produced.
M Phase
Replicated centrioles split and start moving to opposite sides of the cell forming asters.
Nuclear envelop disappears.
Replicated chromatin shortens, thickens and forms chromatid pairs
Early Prophase
M Phase
Centrioles have reached opposite poles of the cell
Spindle forms Plant cells have no
centrioles but the mitotic spindle still forms in a similar manner.
Chromatid pairs float throughout the cytoplasm.
Late Prophase
M Phase
Chromatid pairs align at the equator of the spindle
Microtubules connect the centromere of each chromosome to the two poles of the spindle.
Metaphase
M Phase
Chromatid pairs split
Spindle fibers contract and the single chromosomes are pulled to opposite poles
Anaphase
M Phase
Often described as the opposite of prophase
Nuclear envelop reappears
The chromosomes unravel to become chromatin
Cleavage furrow begins to form (cytokinesis)
Early Telophase
M Phase
Cleavage furrow completes it’s indentation.
“Mother” cell splits into 2 identical “Daughter” cells in a process called cytokinesis
Late Telophase
M Phase
This is the last stage of the cell cycle. Cytokinesis takes place during telophase. Cytokinesis starts with the cleavage furrow and continues
until the cytoplasm is in two separate parts and two new daughter cells have formed.
In plants a structure referred to as the cell plate forms between the two nuclei.
This cell plate gradually forms into a separating membrane. A cell wall then begins to form inside the cell plate
Cytokinesis
M Phase
Cytokinesis in plants
Activity
Draw a DNA triplet with the base sequence TAG on the left side. Make the 5’ the top left
Summary of Cell Division Prophase:
Replicated chromatin condense into chromatid pair Centrioles move to opposite poles Nuclear envelope disappears Spindle fibers start to form
Metaphase Chromatid pairs line up at the equator
Anaphase Chromatid pairs split Chromosomes are pulled to opposite poles by the spindle fibers
Telophase Chromosomes de-condense into chromatin Nuclear envelope reappears Cytoplasm is divided into 2 cells Cytokinesis
Try these….
1. Cells divide to keep cells sizes small for greater _________.
2. As a cell becomes larger its ________ increases faster than its _________.
3. As a cell grows, it places more demands on its _____.4. Division of the cell nucleus is called ________.5. Division of the ________ is called cytokinesis.6. The four phases of the cell cycle are _____, _____,
_____and _______.7. Cells carry out their specialized functions during _______.8. During the ______, DNA replicates.
9. The enzyme _______ “unzips” the DNA, the enzyme __________attached free floating nucleotides.
10. The ____________breaks down during prophase11. Spindle fibers contract and the single chromosomes
are pulled to opposite poles during _________.12. During metaphase, _________align at the equator of
the spindle13. Chromosomes unravel to become chromatin during
________.
Try these….
1. Cells divide to keep cells sizes small for greater efficiency.2. As a cell becomes larger its volume increases faster than its
surface area.3. As a cell grows, it places more demands on its DNA.4. Division of the cell nucleus is called mitosis.5. Division of the cytoplasm is called cytokinesis.6. The four phases of the cell cycle are G1 phase, S phase, G2
phase and M phase.7. Cells carry out their specialized functions during G1 phase.
8. During the S phase, DNA replicates.
9. The enzyme helicase “unzips” the DNA, the enzyme DNA polymerase attached free floating nucleotides.
10. The nuclear envelope breaks down during prophase11. Spindle fibers contract and the single chromosomes
are pulled to opposite poles during anaphase.12. During metaphase, chromatid pairs align at the
equator of the spindle13. Chromosomes unravel to become chromatin during
telophase.
I don't watch television when I can talk about Cell Division!
G0 Phase
Certain cells lose their ability to divide.
They do not replicate their centrioles.
They enter the Gap 0 stage
Examples are neurons of the spinal cord / brain cells
Mitosis in Plant Cells
Mitosis in Animal and Plant Cells
Plant Cells Animal Cells
Cancer
Starts with a single cell that loses its control mechanisms due to a genetic mutation (mistakes in DNA replication)
Can be caused naturally or by carcinogens (i.e.: tobacco smoke, chemicals, etc.)
That cell starts dividing without limit, possibly killing the host (without treatment)
Cancer
Cancer Treatment Three basic treatments:
Surgery to remove cancer Radiation to kill affected cells New drugs are becoming available (Chemotherapy)
It is hard to remove cancer (tumors often lack clear boundaries) Some tumors are very small and are found throughout the body (advanced
stages) Radiation and chemotherapy are aimed at killing cancer cells
The body then has to replace those dead cells which requires a lot of energy Therefore treatment must be balanced with overall patient health
Unfortunately due to natural selection cancer that seems to have disappeared can come back in the future in a form that is resistant to the radiation / chemotherapy
Using multiple drugs can decrease the risk of relapse Multiple drugs decrease the probability of cells acquiring immunity
Another Type of Cell Division - Meiosis
Special cell division that produces Haploid sex cells
Consists of one replication and two cell divisions