Cell Cycle, Mitosis - Loudoun County Public · PDF fileCell Cycle, Mitosis ... METAPHASE 3) ANAPHASE 4) TELOPHASE ... prepped slide? Summary. Title: Microsoft PowerPoint - Cell Cycle,
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Cell Cycle, Mitosis
How do little elephants grow up to be BIG elephants?
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Why do animals shed their skin?
The process of asexual
reproduction begins after a sperm fertilizes an egg.
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Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.
Cell that reproduce by asexual reproduction reproduce constantly.
Three reasons why cells reproduce by asexual reproduction:
• Growth
• Repair
• Replacement
Cells Multiply By Dividing
� Eukaryotes:
� Mitosis
� Meiosis
� Prokaryotes:
� Prokaryotic (binary) fission
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Mitosis is Nuclear Division
Chromosomes
� Chromosomes - contain the genetic information (DNA) that is passed from parent to offspring.
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Chromosomes� Chromosomes have two parts: chromatids held
together by a centromere.
� The chromatids are exact copies of each other and are split apart during mitosis to form single chromosomes.
Centromere
Chromatids
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Chromosome Replication
Replication
One chromatid
sister chromatids
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When cells
divide, sister
chromatids
separate so that
each cell has the
correct number of
chromosomes.
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46 … or … 23?
� 23 homologous pairs of (human) chromosomes (46 total, full number)
� Somatic (body) cells (every cell except sperm and egg)
• 23 individual chromosomes (halfthe full number)
• Gametes (Sex Cells: sperm and egg)
Diploid Haploid
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Human Chromosomes
� Human diploid cells have
46 CHROMOSOMES – 2 COPIES OF 23 DIFFERENT CHROMOSOMES.
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The Cell Cyclefor Somatic Cells (p244-245)
� 2 Main Parts1) Interphase (life,
growth)
2) Mitosis (division of nucleus)
� Consider cytokinesis(division of cytoplasm) as part of mitosis
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2
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Interphase
� Longer part of the
cell cycle (90%)
� 3 Phases
I. G1 (Gap)
II. S (Synthesis)
III. G2 (Growth)
During Interphase, DNA is
relaxed and spread out thinly
Thin, stringy, “Invisible,” chromosomes are
called CHROMATIN
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The 3 Phases of Interphase1. G1 (Gap): Cell is living, doing
normal processes
2. S (Synthesis): DNA replicates
3. G2 (Growth): Cell is expanding, replicating organelles, getting ready for division
� No turning back after S phase starts! Cell will divide!
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What happens after interphase?
MITOSIS
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Cell Division
� Mitosis is NUCLEAR division
� Cytokinesis is CYTOPLASMIC division
� We will call both (together) “Mitosis”
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Check Point:
Why Do Cells Divide?
1. Growth
2. Repair
3. Reproduction
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Mitosis
Meiosis
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In Mitosis: diploid, somatic cells divide to become
daughter cells
(mitosis makes exact copies of cells)
� (*circle*) … diploid / haploid
� (*circle*) … somatic / gamete
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Mitosis Has 4 Main Phases Plus Cytokinesis (p246)
1) PROPHASE
2) METAPHASE
3) ANAPHASE
4) TELOPHASE
• (With Cytokinesis)
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Before we go any further,
Let’s Learn Some Helpful Hand Signs!
PROPHASE
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METAPHASE
ANAPHASE
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TELOPHASE
Got It?
Now we’ll talk about what happens in …
Prophase Metaphase
Anaphase Telophase
P M
A T
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Make A Table
PROPHASE METAPHASE ANAPHASETELOPHASE & CYTOKINESIS
WHAT IT LOOKS LIKE
WHAT’S GOING ON
PROPHASE
� Chromatin thickens into chromosomes
� Nuclear envelope disintegrates
� Centrioles migrate to opposite poles
� Centrioles begin producing spindle fibers
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Centrioles
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METAPHASE
� Chromosomes line upalong metaphase plate
Spindle fibers
are made of
microtubulesSpindle fibers
attach at the
centromere of
duplicated
chromosomes
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ANAPHASE
� Sister chromatids pulled apart to opposite
poles
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TELOPHASE & CYTOKINESIS
� Nucleus reforms
� Chromosomes begin to relax into chromatin (back to G1)
� Cytoplasm splits to separate daughter cells
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CYTOKINESIS (p248)
� Cleavage Furrow
� (no cell wall)
In Animal Cells In Plant Cells
• Cell Plate
• (to form cell wall)
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What could happen if cytokinesis fails?
Can You Identify
The Phases Of
Mitosis?
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Could you find the phases on a
prepped slide?
Summary
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