cell division 2014

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www.tastafe.tas.edu.auCell Division

Document Title (Editable via Slide Master) | Page #22Cell division is necessary for bodily growth, repair and reproduction

Herlihy 2011, p. 41

Document Title (Editable via Slide Master) | Page #

43The frequency of cell division varies from one tissue to the next

Some cells reproduce frequently whereas some reproduce slowly or not at all


44Cells that are replaced very frequentlyMore than 2,000,000 red blood cells are replaced every second!

sfdm.scad.edu


55Cells that line the digestive tract are reproduced very few days ..scitechdaily.com

Document Title (Editable via Slide Master) | Page #66Certain nerve cells in the brain and spinal cord do not reproduce at all

newswatch.nationalgeographic.com


7There are Two (2) Kinds of Cell Division

MitosisMeiosis

Document Title (Editable via Slide Master) | Page #8MitosisIs involved in bodily growth and repair

Mitosis involves the splitting of one mother cell into two (2) identical daughter cells

Herlihy 2011, p.41

Document Title (Editable via Slide Master) | Page #9Mitosis continuedIn mitosis, the exact copy of genetic information, stored within the chromosomes, must be passed from the mother cell to the two daughter cells.

Herlihy 2011, p.41

Document Title (Editable via Slide Master) | Page #10MeiosisMeiosis occurs only in sex cells and is a special kind of cell division

See:

http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter28/animation__how_meiosis_works.html

Document Title (Editable via Slide Master) | Page #biology.clc.uc.edu11Back to Mitosis and the Cell CycleThe cell cycle is the sequence of events that the cell goes through from one mitotic division to the next

Document Title (Editable via Slide Master) | Page #12The Cell CycleThe Cell Cycle is divided into two (2) major phases

Interphase

2. Mitosis

Document Title (Editable via Slide Master) | Page #13 InterphaseDuring this time the cell carries on with its normal functions and gets ready for mitosis through growth and DNA replication

Interphase has three (3) parts to it

First gap phase (G1)Phase SSecond gap phase (G2)

Document Title (Editable via Slide Master) | Page #14FIRST GAP PHASE (G1)The cell carries on it normal activities and begins to make DNA and other substances necessary for cell division

apbio82007.blogspot.com

Document Title (Editable via Slide Master) | Page #zebrafish.umdnj.edu15PHASE (S)During Phase (S) the cell duplicates its chromosomes and makes enough DNA for two (2) identical cells

Document Title (Editable via Slide Master) | Page #16SECOND GAP PHASE (G2)This phase is the final preparatory phase for cell division (mitosis)

It includes the synthesis of enzymes and other protein needed for mitosis

At the completion of G2 the cell enters into the mitotic (M) phaseHerlihy 2011, p.41

Document Title (Editable via Slide Master) | Page #17MITOSIS (M Phase)During M Phase the cell divides into two (2) cells in such a way that the nuclei of both cells contain identical genetic information

Herlihy 2011, p.41

Document Title (Editable via Slide Master) | Page #18

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

Mitosis has four (4) phases:

ProphaseMetaphase AnaphaseTelophase

Document Title (Editable via Slide Master) | Page #19What Next?At the end of mitosis the daughter cells have a choice of two pathways:

Enter G1 and repeat the cycle and divide again

Enter G-zero (G0) and drop out of the cell cycle and rest; they do not undergo mitosis.

Document Title (Editable via Slide Master) | Page #20HOW LONG CAN CELLS REST FOR?Cells may re-enter the cell cycle after days, weeks or even years

Cancer cells do not appear to be able to stop cycling or enter the G0 phase

Cancer cells constantly divide and proliferateHerlihy 2011, p.42

Document Title (Editable via Slide Master) | Page #21TREATING CANCERAnti-cancer drugs work more successfully on cells that are cycling rather than ones that are resting in the G0 phase

Tumours that contain many cycling cells respond best to chemotherapy

Document Title (Editable via Slide Master) | Page #22Anticancer drugs are classified according to the cell cycle phase they affect

Some anti-cancer drugs are called cell cycle-phase specific

These drugs affect cells when they are in a particular phaseANTI CANCER DRUGSHerlihy 2011, p.42

Document Title (Editable via Slide Master) | Page #23For Example

The anti-cancer drug methotrexate is cell cycle S phase specific

Some drugs work in the M phase or in the G2 phase

Other anti-cancer drugs can work in any phase of the cell cycle and are called cell cycle-phase non specific

http://www.oncolink.org/treatment/section.cfm?c=9&s=70


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24CELL DIFFERENTIATION

Mitosis ensures that when one cell divides it produces two (2) identical cells

An embryo begins life as a single cell, the fertilised ovum, and through mitosis the single cell divides many more times into identical cellsHerlihy 2011, p.42


25Sometime during their development the cells begin to specialise, or differentiate

One cell may switch on enzymes that make red blood cells while another cell may make bone cells

We all begin life as one cell and end up as billions of specialised cells


26When differentiation goes wrong!When a sample of tissue (a biopsy) is surgically removed for examination it may show many poorly differentiated cells

This means that the cells have failed to differentiate or specialise.


27

For example un-differentiated cells found in a liver tumour do not resemble normal liver cells

Failure to differentiate is characteristic of cancer cells Herlihy 2011, p.42

Document Title (Editable via Slide Master) | Page #28bjui.org

BLADDER CANCER


29STEM CELLSStem cells are relatively un-differentiated or un-specialised cells and their job is to produce additional un-specialised cells

Every time a stem cell divides one of the daughter cells differentiates while the other daughter cell prepares for further stem cell division

The rate of stem cell division varies with the tissue type

Document Title (Editable via Slide Master) | Page #30For Example

Stem cells in the bone marrow and skin are capable of dividing more than once a day, but adult cartilage stem cells may remain inactive for years.

With ongoing ethical research there may be the potential here to replace damaged body components, like the spinal cord for example.

Herlihy 2011, p.43

Document Title (Editable via Slide Master) | Page #31ORDER & DISORDERMost cell growth is orderly, but sometimes this process becomes disorderly and un-controlled

When too many cells are produced a lump or a tumour forms.

Tumours are either benign (not cancerous) or malignant (cancerous).

Herlihy 2011, p.43


Malignant Breast Tumour


Benign Breast Tumour (mammogram)


34PROGRAMMED CELL DEATHThis process is known as apoptosis and is essentially cell suicide

Apoptosis helps ride the body of old, un-necessary and unhealthy cells.

The body produces a million cells per second the elimination of some cells by apoptosis is necessary

Herlihy 2011, p.43


35Apoptosis can become uncontrolled and this results in excessive cellular death and disease

apoptosis-networks.eu

Document Title (Editable via Slide Master) | Page #36When cancer cells spread they are said to metastasise

Sometimes cells are so badly injured that they die or necrose.

Herlihy 2011, p.44


37REFERENCEHerlihy, B. (2011) The Human Body in Health and Illness, 4th Edition, Elsevier Saunders


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cell division 2014

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