What is Mitosis?

• A form of cell division.

• Asexual reproduction in unicellular organisms.

• Growth and Repair in multicellular organisms.

Types of Asexual Reproduction• Fission

The equal splitting of a cell through mitosis to form two new cells.

• BuddingThe unequal splitting of a cell through mitosis to form on parent cell and one daughter cell.

Why do Cells Reproduce?

1. To make more organisms of the same species (unicellular organisms).

2. To grow (multicellular organisms)3. To repair damaged tissues (multicellular

organisms).

Why does Mitosis occur?• When cells get too big they can no longer

get enough nutrients through the cell membrane in order to sustain it’s entire self.

• In other words it does not have enough surface area to diffuse in enough nutrients or diffuse out all wastes.

Mitosis can be explained in Phases

• Regular cell activity and Mitosis can be explained in 5 basic phases.

• The phases are Interphase, Prophase, Metaphase, Anaphase and Telophase.

Interphase

• Normal activities of the cell are performed.

• Chromatin is doubled at the end of this phase.

ChromatinChromatin

Interphase – In Between

Prophase

• Chromatin condenses into chromosomes.

• Centrioles migrate to the poles.

• Spindle fibers begin to form.• Nuclear membrane begins to

break down.Prophase - “Preparing”

Doubled Chromosomes

Sister Chromatids

Metaphase

• Chromosomes line up on the equatorial plane.

Metaphase – “Middle”

Pole

Equator

Anaphase

• Spindle Fibers pull the Sister chromatids apart.

• Single chromosomes move toward the poles.

Anaphase – “Away” or “Apart”

Telophase

• Single stranded chromosomes arrive at the poles.

• Nuclear membranes form.• Cytokinesis (pinching in)

begins.Telophase – “Two”

How can we remember all these phases?

• I . P . M . A . T.

Animations

• Mitosis Animation

• Mitosis by a spanish Robert Miles

• Pokemon Mitosis

Meiosis Mitosis

End resultNormally four cells, each with half the number of chromosomes as the parent

Two cells, having the same number of chromosomes as the parent

FunctionSexual reproduction, production of gametes (sex cells)

Cellular reproduction, growth, repair, asexual reproduction

Where does it happen? Animals, fungi, plants, protists All eukaryotic organisms

StepsProphase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II

Prophase, Metaphase, Anaphase, Telophase

Genetically same as parent?

No Usually

Crossing over happens? Yes, in Prophase I Sometimes

Pairing of homologous chromosomes?

Yes No

Cytokinesis Occurs in Telophase I and Telophase II Occurs in Telophase

Centromeres splitDoes not occur in Anaphase I, but occurs in Anaphase II

Occurs in Anaphase

Meiosis vs. mitosisIn order to understand meiosis, a comparison to mitosis is helpful. The table below shows the differences between meiosis and mitosis.