cell division
TRANSCRIPT
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Bellringer
• How are chromotin and chromosomes different ?
• Explain what Binary Fission is?
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Agenda
• NOTES: Cell Division– Purpose of Division– Chromatin & Chromosomes– Binary Fission (bacteria division)– Cell Cycle (eukaryotic division)– Introduction to Steps of Mitosis
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Why do cells divide?• Unicellular creatures divide
as a way to reproduce. Their “children” are just separated halves of the “parent”.
• Multicellular lifeforms divide their cells in order to grow larger and to replace dead cells. Your body replaces about 300,000 cells each minute.
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Parent and Daughter Cells• Cell division creates 2 identical copies
– The cell that is divided is called the “Parent Cell”
– The 2 new cells are called “Daughter Cells”
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Parent CellParent Cell
Two Two identical identical daughter daughter
cellscells
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Daughter Cell DNA• Remember that DNA carries all of the
instructions for a cell.
• Every daughter cell needs a complete set of its parent’s DNA. Without a full set information would be lost.
• This means that a parent cell must create two sets of DNA before dividing so each daughter can have one.
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Chromatin & Chromosomes• DNA is usually packed loosely within the
cell. DNA in this “normal” state is called chromatin.
• Before dividing, a cell’s DNA will form large, tightly packed clumps called chromosomes. This is done to allow pieces of DNA to be easily sorted and moved around.
• After dividing, a chromosome will loosen up and the DNA converts back into chromatin.
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ChromosomChromosomeses
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CHROMATIN ~~~~~ CHROMOSOMES
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Cell Division in Cell Division in ProkaryotesProkaryotes
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Prokaryotic ChromosomeProkaryotic Chromosome
• Remember that Remember that prokaryotes have no prokaryotes have no nucleus to contain nucleus to contain DNADNA
• Their DNA forms one, Their DNA forms one, circular chromosome circular chromosome attached to the inside attached to the inside of the cell membraneof the cell membrane
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Cell Division in Cell Division in ProkaryotesProkaryotes
Prokaryotes such as Prokaryotes such as bacteria divide by a quick bacteria divide by a quick and simple process called and simple process called binary fissionbinary fission
First the single First the single chromosome makes a copy chromosome makes a copy of itselfof itself
A cell wall then forms A cell wall then forms between the chromosomes between the chromosomes dividing the celldividing the cell
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Prokaryotic Division Video
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Eukaryotic Division: Cell Cycle
• Eukaryotic cells divide by a longer and more complex method known as the cell cycle.
• There are 4 stages of the cell cycle. – G1: First Growth
– S: Synthesis Stage
– G2: Second Growth
– M: Mitosis
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GG11 Stage Stage• GG11 is the first growth stage of a is the first growth stage of a
newly created cell.newly created cell.
• The cell matures by growing larger The cell matures by growing larger and creating more organelles.and creating more organelles.
• Cell carries on its normal Cell carries on its normal metabolic activitiesmetabolic activities
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S StageS Stage• S is the synthesis stage. The cell copies S is the synthesis stage. The cell copies
all of its DNA to make a second set. all of its DNA to make a second set. • This prepares for division at later stagesThis prepares for division at later stages
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GG22 Stage Stage• This second growth stage This second growth stage
occurs after DNA has been occurs after DNA has been copiedcopied
• The cell begins creating The cell begins creating specialized organelles and specialized organelles and structures that will do the work structures that will do the work of dividing.of dividing.
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Cell CycleCell Cycle
DaughteDaughter Cellsr Cells
DNA DNA CopiedCopied
Cells Cells MaturMatur
ee
Cell prepares Cell prepares for Divisionfor Division
Cell Divides into Cell Divides into Identical cellsIdentical cells
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M stageM stage• Mitosis is the division process.Mitosis is the division process.
• During this time DNA clumps During this time DNA clumps into chromosomes and then is into chromosomes and then is separated into two groups.separated into two groups.
• When the cell divides, each When the cell divides, each daughter receives half of the daughter receives half of the chromosomes. chromosomes.
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5 Stages of Mitosis• Mitosis is divided into 5 steps that we
will study in detail in future lessons.– Prophase– Metaphase– Anaphase– Telophase– Cytokinesis
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Cell Cycle Summary Video
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