mitosis unit

MITOSIS UNITChapter 10; Cell Growth and Division Prentice Hall Biology

How do little puppies grow up?

When I get a cut, how do I heal?

Vocabulary before we get started:

DNA: DeoxyriboNucleic Acid—The genetic material of all of life! DNA is made up of nucleotides, and is the basis of all natural heredity traits of an organism.


Prokaryotes- ‘Simple’ one-celled organisms that do not have a nucleus. › Bacteria and Archeabacteria.

Eukaryotes- ‘Higher’ organisms that have a nucleus and a more complete DNA.


Centriole —Organelles found in animal cells that help with the process of mitosis

Centromere —The area where sister chromatids are held together.


Homologous Chromosome — A pair of similar chromosomes. In most organisms, one of these chromosomes came from the father, and the other chromosome came from the mother.

Sister Chromatid —A sister chromatid is two copies of the same DNA sequence, held together by a centromere.


Chromatin — A thread-like mass of DNA seen in the nucleus during most of the a cell’s life

Chromosome — a rod-like bundle of DNA seen during mitosis.


Mother Cell — A cell that is about to divide by mitosis.

Daughter Cells — The two cells that result from mitosis. Daughter cells will have identical DNA to each other, which is the same DNA that the mother cell had.

Mitosis Mitosis is the process of asexual cell

division. › Mitosis brings about growth &

development› Mitosis enables healing when we get cut.

Mitosis creates two identical cells from one cell. › Each cell will have a full copy of the

original DNA.

Why are we made up of so many tiny cells?

Wouldn’t it be easier to just have fewer and larger cells?

Cells are bustling with activity! They need proteins and smaller inorganic compounds to come in to and move out of the cell. They use these resources all throughout the cell, and every organelle needs to have access to these resources.



If a cell becomes bigger, the ratio of its surface area to its volume decreases. With a poorer ratio, resources can’t move into the cell quick enough to reach all of organelles.



Also:There is only one area in the cell where there is DNA, yet all of the cell needs the proteins that are made from the DNA. If a cell becomes too large, the demand on the DNA to copy the necessary genes for all of the cell to function becomes too great.

Interphase The majority of the cell cycle.

• Interphase is made up of the G1, S, and G2 phases of the cell cycle.

• During this phase, chromosomes are copied.• Chromosomes appear as threadlike coils

(chromatin) during this phase. Nucleus

Cytoplasm

Cell Membrane

The bigger picture:The Cell Cycle!

Interphase is made up of the G1, S, and G2 phases of the cell cycle. G1

PhaseS

Phase

G2 Phase

M Phase

The Cell Cycle

InterphaseAnimal Cell Plant Cell

Prophase 1st step in Mitosis

• The nuclear membrane breaks down.• The chromatin condenses, and

chromosomes become visible• Centrioles appear and begin to move to

opposite end of the cell. • Spindle fibers form between the centrioles.

Centrioleschromosomes

Spindle fibersNuclear membrane

ProphaseAnimal Cell Plant Cell

Spindle fibers

Metaphase 2nd step in Mitosis

• Sister chromatids line up at the mid-line of the cell.

• Centromeres (the area where the sister chromosomes are held together) attach to the spindle fibers.

Centrioles

Spindle fibers

MetaphaseAnimal Cell Plant Cell

Anaphase 3rd step in Mitosis

• Spindle fibers pull apart the centromeres of the sister chromatids.

• Each centriole pulls one of the sister chromatids to its pole.

Centrioles

Spindle fibers

AnaphaseAnimal Cell Plant Cell

Telophase 4th step in Mitosis

• Two new nuclear membranes form. • Chromosomes begin to appear as chromatin

(threads rather than rods).• Spindle fibers break down.• Mitosis ends.

Nuclear Membrane

NuclearMembrane

Chromatinforming

TelophaseAnimal Cell Plant Cell

Cytokinesisafter mitosis

• In animals: cell membrane pinches inward

to create two daughter cells – each with its own nucleus with identical chromosomes.

• In plants: a cell wall forms between the newly divided cells.

Animal Mitosis -- Review

Interphase

Prophase

Metaphase

Anaphase

Telophase

Interphase

A review of mitosis:

Mitosis animation Cell animations

A short film on mitosis.

http://www.cellsalive.com/mitosis.htm

http://plaza.ufl.edu/alallen/pgl/modules/rio/stingarees/module/why.html

http://www.hybridmedicalanimation.com/work/animation/the-stages-of-mitosis/


Mitosis is a very controlled process that only occurs in a small fraction of the cell’s life G1

PhaseS

Phase

G2 Phase

M Phase

The Cell Cycle

How do little puppies grow up?Mitosis is the process that allows living things to

grow. Without mitosis we wouldn’t ever grow and develop. So if we were to stop the mitosis in this puppy, we would be preventing it from ever getting any bigger.

Mitosis is involved in healing after an injury. If we get a cut or a scrape, our body uses mitosis to heal itself.

When I get a cut, how do I heal?

Summary Thoughts:Every type of organism must grow and develop and then reproduce in order to continue the species.

For eukaryotes, mitosis is the process by which organisms grow and develop. A hallmark of higher-order life is having a multi-cellular body, but since reproduction gives only a single fertilized cell, the cell must divide over and over again in order to make an organism. Mitosis is the process across all of the eukaryotic kingdoms by which this growth and development occurs.

Closing questions:On a half-sheet of paper, answer these questions:

1. How could you describe the cells that result from Mitosis?1. They contain no organelles.2. They are the same as the cell prior to mitosis.3. They contain half of the amount of DNA of the original

cell. 4. They must be either plant or animal cells.

2. What are the four main stages of Mitosis?1. 2. 3. 4.

Closing questions:On a half-sheet of paper, answer these questions:

3. Describe what happens during interphase:

4. Describe the role of spindle fibers in mitosis. In what stage do they appear? Where do they connect to? When do they disappear?


The duration of the cell cycle varies in in different organisms, different tissues, and at different points in development, but it is a very controlled process.

G1 Phase

S Phase

G2 Phase

M Phase

The Cell Cycle

How is the Cell Cycle Regulated?

The cell cycle is regulated by a protein called cyclin.

The cell cycle is also regulated with ‘Internal regulators.’

The cell cycle is also regulated by ‘external regulators.’

What if the regulation fails? If a cell has too many cyclins, if the

internal regulators fail, or if there are external regulators that are constantly signaling for mitosis to occur, a cell will continue to divide without stopping.

A scenario where a cell is continually dividing when it shouldn’t be is called uncontrolled cell growth.

Uncontrolled Cell Growth