Mitosis and the Cell CycleMitosis and the Cell Cycle

Mrs. Schenfield’s Mrs. Schenfield’s

88thth Grade Life Science Grade Life Science

The Importance of MitosisThe Importance of Mitosis

Growth and RepairGrowth and Repair Reproduction of single celled Reproduction of single celled organisms.organisms.

The need to heal!The need to heal!

The need to grow!The need to grow!

Cell CycleCell Cycle

95% of cell cycle in interphase95% of cell cycle in interphase5% of cell cycle in mitosis 5% of cell cycle in mitosis

ending with cytokinesis.ending with cytokinesis.

Cell Cycle-Interphase (G1, S, G2)Cell Cycle-Interphase (G1, S, G2)

G1 = cell growsG1 = cell grows S = genes (DNA) S = genes (DNA)

duplicatedduplicated G2= Prepares to divideG2= Prepares to divide

M= Mitosis-cell M= Mitosis-cell

goes through prophase,goes through prophase,

metaphase, anaphase,metaphase, anaphase,

and telophase.and telophase.

INTERPHASE

“G1” or Growth 1 phase (Interphase)

“S” or DNASynthesis (Genes copied)

G2 or Growth 2 phase-Preparesto become two cells.

“M” orMitosisphase

DNA Replication – Simple in Principle, Complicated in Practice

How are genes How are genes duplicated?duplicated?

During the “S” During the “S” period of period of interphase the interphase the DNA uncoils and DNA uncoils and an exact copy is an exact copy is made of each made of each side.side.

DNA is Packaged into Chromosomes

DNA is packaged into DNA is packaged into chromosomes.chromosomes.

The Link Between DNA Replication and Chromosome Duplication

ChromosomesChromosomes Chromosome- Chromosome-

consists of two consists of two identical halves identical halves connected together connected together by a centromere.by a centromere.

Chromatid- a half of Chromatid- a half of one chromosome.one chromosome.

Contains one Contains one complete set of complete set of informationinformation

Copies itself to Copies itself to make the other make the other chromatidchromatid

DNA is Condensed into Visible Chromosomes Only For Brief Periods in the Life of a Cell

95% of the time, chromosomes are like this.

Chromosomes can be seen 5% of the time in an actively growing cell and less in a non-growing cell.

Cell division requires coordinated division of chromosomes (mitosis) …..

…… and division of the cytoplasm (cytokinesis).

Stages of MitosisStages of Mitosis

ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase CytokinesisCytokinesis

Cancer Is One Outcome of A Runaway Cell Cycle

Picture of prostate cancer cells during division.

The Knit of Identity - Mitosis Precisely and Evenly Divides Duplicated Chromosomes

Dividing the duplicated chromosomes in the phases of mitosis provides each new cell with an identical and

complete set of genes.

interphase Prophase Metaphase

The sister chromatids line

up at the center of the spindle.

Mitosis Precisely and Evenly Divides Duplicated ChromosomesCytokinesis is the process of cell division and

it is distinct and separable from mitosis.

Mitosis in Action

.

Blue shows DNA, green shows spindle Blue shows DNA, green shows spindle fibers.fibers.

Interphase Early prophase Late prophase

Early metaphase

Metaphase Early anaphase Late anaphase Late telophase

In Animal Cells, a Cleavage

Furrow Forms and Separates

Daughter Cells

(Cytokinesis)

Actual picture of a cell using an electron microscope.

Cleave furrow in a dividing frog cell.

The Plant Cell Wall Forces Cytokinesis to Play by Different Rules

Use your notes to identify the stage Use your notes to identify the stage of mitosis each cell is in. of mitosis each cell is in.

Cell #1 Cell #2

Stage?Stage?

Cell #3Cell #3

Cell #4

Stages?Stages?

Cell #5 Cell #6

Stages?Stages?

Cell #7Cell #7

Cell #8