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Mitosis

Duplication and Division

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Cell cycle

Two main periods

Mitotic phase is a relatively short action-packed period.Interphase

Much longer period, where the cell prepares itself for division.The cell grows by producing proteins andcytoplasmic organelles

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Homologous Chromosomes

Sister Chromatids

Chromosome Replication

When a chromosome divides into identicalchromosomes, the chromatids remainattached at their centromere.

DNA unzips and is duplicated

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Interphase

Stage between cell divisionsDivided into three phases

G1 (first gap) - a cell growsS (synthesis) - continues to grow as someDNA is replicated

The chromosomes begin to replicateG2 (second gap) - grows more and preparesfor mitosis

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Mitotic Phase

MitosisProcess by which a cell separates its

duplicated genome into two identical halves.Cytokinesis

Divides the cytoplasm and cell membraneResults in two identical daughter cells with aroughly equal distribution of organelles andother cellular components.

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Mitosis - 5 subphases

ProphasePrometaphase

MetaphaseAnaphaseTelophase

Impossible to discern an exact "start" and "stop"of the phases.

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Prophase

ChromatinSmall granular particles in the nucleus beginsto condenseBecome visible in the light microscope aschromosomes.

The nucleolus disappears.

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Prophase

CentrioleCytoplasmic organelle – divides into two

Begin moving to opposite ends of the cellFibers extend from the centromeres.

Spindle fibersLong protein moleculesForm a three dimensional arch across the cellbetween the two bodies

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Prometaphase

The nuclear membrane dissolvesProteins attach to the centromeres

creating the kinetochores.links the chromatids to microtubule polymersfrom the mitotic spindle

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PrometaphaseChromosome number is temporarily double –tetraploid

Chromatids become thicker

Can identify lengths and location of centromeresKinetochores of each chromatid move to thespindles equator

MetaphasePro metaphase

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Metaphase

Spindle fibers align the chromosomes

along the middle of the cell – metaphaseplate.Necessary to ensure when the chromatids

are separated, each new nucleus willreceive one copy of each chromosome

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Anaphase

The paired chromatids separate at thekinetochores and move to opposite sidesof the cell.

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Anaphase

Even alignment is due to thecounterbalance of the pulling powersgenerated by the opposing kinetochores,analogous to a tug-of-war between equallystrong people

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Telophase

The chromosomes disperse and are nolonger visible under the light microscope.The spindle fibers disperse.

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Cytokinesis

A fiber ring composed of actin (protein) isformed around the center of the cell

Contracts pinching the cell into twodaughter cells, each with one nucleus.

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Review

Each daughter cell has a complete copy of the genome of its parent cell.

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Interphase

Review