1 1 asexual reproduction the cell cycle. 2 dna must be copied or replicated before cell division dna...
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Asexual Reproduction
The Cell Cycle
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DNA must be DNA must be copied or copied or replicatedreplicated before cell before cell division division
Each new cell Each new cell will then have will then have anan identical identical copy copy of the of the DNADNA
Original DNA Original DNA strandstrand
Two new, Two new, identical DNA identical DNA strandsstrands
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Parent CellParent Cell
Two Two identical identical daughter daughter cellscells
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The DNA of The DNA of prokaryotes prokaryotes (bacteria) is (bacteria) is
one, circular one, circular chromosome chromosome attached to the attached to the inside of the inside of the cell membranecell membrane
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AllAll eukaryoticeukaryotic cells store cells store genetic information in genetic information in chromosomeschromosomes
Most eukaryotes have between Most eukaryotes have between 10 10 and 50 chromosomesand 50 chromosomes in their body in their body cellscells
Human body cells Human body cells havehave 4646 chromosomes or 23 identical pairschromosomes or 23 identical pairs
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Each chromosome is composed Each chromosome is composed of a of a single, tightly coiled DNA single, tightly coiled DNA moleculemolecule
ChromosomesChromosomes can’t be seen can’t be seen when cellswhen cells aren’t dividingaren’t dividing and and are called are called chromatinchromatin
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Duplicated chromosomes are called chromatids & are held together by the centromere
Called Sister ChromatidsCalled Sister Chromatids
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AA picturepicture of the of the chromosomes chromosomes from a human cell from a human cell arranged in pairs arranged in pairs by sizeby size
First 22 pairs are First 22 pairs are called called autosomesautosomes
Last pair are the Last pair are the sex chromosomessex chromosomes
XXXX female or female or XY XY malemale
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Y - ChromosomeY - Chromosome
X - ChromosomeX - Chromosome
The Y Chromosome DecidesThe Y Chromosome Decides
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Prokaryotes such Prokaryotes such as as bacteriabacteria divide divide into 2 identical into 2 identical cells by the process cells by the process of of binary fissionbinary fission
Single chromosome Single chromosome makes a copy of makes a copy of itselfitself
Cell wall forms Cell wall forms between the between the chromosomes chromosomes dividing the celldividing the cell
Parent cellParent cell
2 identical daughter cells2 identical daughter cells
Chromosome Chromosome relicatesrelicates
Cell splitsCell splits
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How do little elephants grow up to be BIG elephants?
The process of asexual reproduction in
eukaryotes begins after a sperm fertilizes
an egg.
Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.
Cancer develops when cells that reproduce by asexual reproduction divide out of control.
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Daughter Daughter CellsCells
DNA CopiedDNA Copied
Cells Cells MatureMature
Cells prepare Cells prepare
for Divisionfor Division
Nuclear DivisionNuclear Division
Cell Divides into 2 Identical cellsCell Divides into 2 Identical cells
Cytoplasmic Division
Animated Cell Cyclehttp://www.cellsalive.com/mitosis.htm
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase & Cytokinesis
• Chromosomes are copied (# doubles)• Chromosomes appear as threadlike coils
(chromatin) at the start, but each chromosome and its copy(sister chromosomes) change to sister chromatids at end of this phase
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11stst growth stage growth stage after cell divisionafter cell division CellsCells maturemature by making more by making more
cytoplasm & organellescytoplasm & organelles Cell carries on its Cell carries on its normal normal
metabolic activitiesmetabolic activities CellsCells can leave can leave this phase (Gthis phase (G00)and )and
go through a go through a rest phaserest phase and then and then reenterreenter before proceeding to the before proceeding to the S phaseS phase
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SynthesisSynthesis PhasePhase DNADNA is copied or is copied or replicatedreplicated
Two Two identical identical copies of copies of DNADNA
Original DNAOriginal DNA
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22ndnd Growth Growth StageStage OccursOccurs after DNA has been after DNA has been
copiedcopied All cell All cell structures needed for structures needed for
division division are made (e.g. are made (e.g. centrioles)centrioles)
BothBoth organelles & proteins organelles & proteins are are synthesizedsynthesized
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What the cell looks likeWhat the cell looks like
Animal Cell
What’s occurring
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
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Division of Division of the the nucleusnucleus
Only occurs in Only occurs in eukaryoteseukaryotes
HasHas fourfour stagesstages
Doesn’t occur Doesn’t occur in some cells in some cells such assuch as brain brain cellscells
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ProProphasephaseMetaMetaphasephaseAnaAnaphasephaseTeloTelophasephase
• Mitosis begins (cell begins to divide)• Centrioles (or poles) appear and begin to move to
opposite end of the cell (animal cells only). • Spindle fibers form between the poles.• Nucleus and nucleolus disappear• Chromatin condenses (coils) to form chromosomes
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Spindle fibers
Centrioles
• Chromatids (or pairs of chromosomes) attach to the spindle fibers.
• Chromosomes are now lined up at Chromosomes are now lined up at the equatorthe equator
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• Occurs rapidly• Chromatids (or pairs of chromosomes)
separate and begin to move to opposite ends of the cell.
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• Two new nuclei and nucleoli form. • Chromosomes appear as chromatin (threads rather
than rods).• Cleavage furrow begins to forms in animal cells
and a cell plate begins to form in plant cells• Mitosis ends.
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• Cell membrane moves inward to divide the cytoplasm and create two daughter cells – each with its own nucleus with identical chromosomes.
Animal Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Plant Mitosis -- ReviewInterphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
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- Cell Division
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http://www.cellsalive.com/mitosis.htm