Mitosis

• Definition: nuclear division and cytokinesis

• Functions:

• tissue growth and repair

• asexual reproduction (binary & multiple

fission)

Cell division requires coordinated division of chromosomes (mitosis)…

…and division of the cytoplasm (cytokinesis).

Because DNA stores genetic information and is faithfully replicated, information is passed largely unaltered from cell-to-cell, generation-to-generation.

Proteins and Their Production

The Primary Reason for DNA

DNA is Packaged into Chromosomes

Two meters DNA fit into a sphere ~ 0.000005 meters in diameter.

chromatin

duplicatedchromosome

The Link Between DNA Replication and Chromosome Duplication

Anatomy of a Chromosome

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

95% of the time, chromosomes are like this.

A Karyotype is an Arranged Picture of Chromosomes At Their Most Condensed State

A normal human karyotype

Boy or girl?

Note that almost all chromosomes come in homologous pairs.

Prophase

• nuclear membrane disintegrates

• chromatin thickens

• spindle apparatus appears

Metaphase

• chromosomes line up on the equatorial plane

Anaphase

• centromers divide

• chromatids move toward opposite poles

Telophase

• nuclear membrane reforms

• cytokinesis

• daughter cells

Cytokinesis

In Animal Cells, a Cleavage Furrow Forms and Separates Daughter Cells

Cleave furrow in a dividing frog cell.

In plants, a cell plate forms; separating daughter cells during cytokinesis

Stages of Mitosis• Prophase– DNA is condensed and packaged

• Metaphase– “middle stage”; Condensed chromosomes line up along the equatorial plane.

• Anaphase- Copies of each chromosome move to opposite poles of the cell.

• Telophase– “end stage”; Nuclear membranes reform around the chromosomes and cytokinesis occurs resulting in two daughter cells.

Cancer is Runaway Mitosis

Licentious division - prostate cancer cells during division.