The Cell Cycle/Mitosis

The cell cycle includes the process in which single cells divide to

form TWO identical cells with the SAME number of chromosomes.

• Fact: Living things grow, or increase in size. Why does this happen?

• A living thing grows because it produces more and more cells.

• If cells simply got BIGGER, they would encounter problems!

Materials will have trouble entering and leaving the cell

An “information crisis” would occur! Not enough DNA to code for all of the proteins the cell would need at a larger size.

I. Why do cells divide?

QQ1

Through what process

do materials enter and

leave the cell?

II. What is a chromosome?

• Structures in the nucleus that contain the genetic information that is passed on from one generation of cells to the next.

Chromosome Structure

• During the first stage of cell division, DNA replicates (copies itself) and condenses around histone proteins to form chromosomes.

• Each chromosome is composed of 2 identical sister chromatids attached by a centromere

QQ2

In what organelle

is the DNA found?

Interphase:

• The period between cell divisions; longest phase in the cell cycle

• Period of intense activity (interphase=intense activity)

• Divided into 3 phases: G1 (cell growth), S (DNA synthesis), G2 (organelles and materials required for cell division are synthesized)

III. Interphase Mitosis in Action

Prophase:

• Chromatin condenses into distinct chromosomes, nucleolus disappears

• Nuclear envelope begins to break down

• In animals, centrioles separate and take position on opposite sides of nucleus

• Spindle begins to form

IV. Mitosis

Metaphase:

• Chromosomes line up across the center of the cell

• Spindle fibers connect to the centromere of each chromosome

Anaphase:

• Centromeres joining the sister chromatids split

• Sister chromatids begin to separate, becoming individual chromosomes

• Anaphase ends when the movement of chromosomes stops

Telophase:

• Chromosomes begin to uncoil into a tangle of chromatin

• Spindle breaks apart

• Nuclear envelopes reform around the chromatin, forming 2 daughter nuclei

• Mitosis is complete!

QQ3

What are the 4

phases of the

mitosis?

Is Cell

Division

complete?

V. Cytokinesis

Cytokinesis:

• To complete the cell cycle, the cytoplasm needs to divide!

• Cytokinesis is the division of the cytoplasm into two individual cells with identical genetic information.

• In plants, a cell plate gradually develops into a separating membrane.

• The Cell Cycle is complete and will begin again!

QQ4

With what phase will the

cell cycle begin? What

happens during that cycle?

http://vcell.ndsu.nodak.edu/animati

ons/mitosis/movie-flash.htm

Clever ways to remember

Interphase – “Inte”nse activity.

Prophase - chromosomes first a"P"pear

Metaphase - chromosomes line up in "M"iddle

Anaphase - they move "A"way

Telophase - you have "T"wo nuclei

Cytokinesis – they divide, don’t you “C”?

iPMAT!

PMAT!

I (interphase)

prefer (prophase)

mice (metaphase)

and (anaphase)

talking (telephase)

cats (cytokinesis) QQ5

Create your own special way!