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A&P I Lab. Eukaryotic cells divide in one of two ways Mitosis Occurs in somatic (non-reproductive) cells Meiosis Occurs in germ (reproductive) cells Results in the production of gametes. Eukaryotes Have a Complex Cell Cycle . - PowerPoint PPT Presentation
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How Cells Divide
A&P I Lab
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Eukaryotes Have aComplex Cell Cycle
Eukaryotic cells divide in one of two ways
MitosisOccurs in somatic (non-reproductive) cells
MeiosisOccurs in germ (reproductive) cellsResults in the production of gametes
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The complex cell cycle of eukaryotic cell is composed of several stages
G1 phasePrimary growth phase
S phaseDNA replication
G2 phaseMicrotubule synthesis
M phaseChromosomes pull apart
C phaseCytoplasm divides
Interphase
Mitosis
Cytokinesis
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How the cell cycle works
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Chromosomes
Humans have 46 chromosomes
This display is termed a karyotype
The 23 pairs of homologous chromosomes can be organized by size
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7.3 Chromosomes
Chromosomes are composed of chromatinComplex of DNA (~ 40%) and proteins (~ 60%)
A typical human chromosome contains about 140 million nucleotides in its DNA
This is equivalent to About 5 cm in stretched length2,000 printed books of 1,000 pages each!
In the cell, however, the DNA is coiled
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Cell DivisionThe eukaryotic cell cycle consists of the following stages
InterphaseMitosis
Division of the nucleus Subdivided into
Prophase, metaphase, anaphase, telophaseCytokinesis
Division of the cytoplasm
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What are collectively known as G1, S, and G2 phases of the cell cycle? During which phase of the cell cycle is DNA synthesized?How many chromosomes do humans have?
Review the Concepts
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InterphaseChromosomes replicate and begin to condense
MitosisProphase
Nuclear envelope breaks downChromosomes condense furtherSpindle apparatus is formed
MetaphaseChromosomes align along the equatorial planeSpindle fibers attach at the kinetochores
On opposite sides of the centromeres
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Fig. 7.7
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MitosisAnaphase
Sister chromatids separateThey are drawn to opposite poles by shortening of the microtubules attached to them
TelophaseNuclear envelope reappearsChromosomes decondense Spindle apparatus is disassembled
CytokinesisTwo diploid daughter cells form
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Fig. 7.7
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Cytokinesis
Animal cells
Plant cells
Cleavage furrow forms, pinching the cell in two
Cell plate forms, dividing the cell in two
