5 Mitosis

19
 Mitosis Duplication and Division

Transcript of 5 Mitosis

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 1/19

Mitosis

Duplication and Division

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 2/19

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 3/19

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 4/19

Homologous Chromosomes

Sister Chromatids

Chromosome Replication

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

DNA unzips and is duplicated

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 5/19

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 6/19

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.

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 7/19

Mitosis - 5 subphases

ProphasePrometaphase

MetaphaseAnaphaseTelophase

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 8/19

Prophase

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

The nucleolus disappears.

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 9/19

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 10/19

Prometaphase

The nuclear membrane dissolvesProteins attach to the centromeres

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 11/19

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 12/19

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 13/19

Anaphase

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 14/19

Anaphase

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 15/19

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 16/19

Telophase

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 17/19

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.

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 18/19

Review

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

8/14/2019 5 Mitosis

http://slidepdf.com/reader/full/5-mitosis 19/19

Interphase

Review