THE CELL CYCLE and CELL DIVISION

THE CELL CYCLE and

CELL DIVISION

Think about it…why do cells stay small?

DNA Overload = Limit to Cell Growth

The information stored in that DNA is able to meet all of the cell’s needs in a small cell

If a cell grows too large, the DNA cannot produce enough proteins to supply the cell

CELL DIVISION-before it becomes too large, a growing

‘parent’ cell divides into 2 ‘daughter’ cells

**Before cell division occurs, the cell replicates all of its DNA, one set/daughter

**2 main stages of eukaryotic cell division:1. Mitosis – division of the cell nucleus2. Cytokinesis – division of cell cytoplasm

Liver cell completes cell division – Magnification 11,500x

Chromosomes Genetic information is passed from one

generation to the next on chromosomes (made of DNA).

Chromosomes are only visible in most cells during cell division (other times, the DNA is in the not visible chromatin state)

Before cell division, the DNA condenses into compact structures, chromosomes

Chromosomes Once copied, each

chromosome consists of two identical “sister” chromatids.

Centromere –attachment

After cell division, each new cell receives one sister chromatid

Centromere

Sister chromatids

THE CELL CYCLE

The Cell Cycle During the cell cycle:

a cell grows prepares for division divides

Interphase is the period of growth that occurs between cell divisions

-followed by mitosis and cytokinesis

The Cell Cycle

Animated Cycle

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

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

increases in sizesynthesizes proteins & organelles

chromosome replicatedDNA synthesis takes place

Enters S phase

completes cycle

organelles and molecules required for cell division are producedOnce G2 is complete, the cell is ready to start the M phase—Mitosis

MitosisThe process of cell division which results

in the production of two daughter cells from a single parent cell

The daughter cells are identical to one another and to the original parent

cell.

Mitosis

Prophase Metaphase Anaphase Telophase

ProphaseSpindle forming

Chromosomes (paired

chromatids)Centromere

Mitosis: PROPHASE

Prophase 1st & longest phase

Centrioles separate and take up positions @ nuclear poles

Spindle, a microtubule structure, forms between the centrioles

Nuclear envelope breaks down.

Spindle forming

CentromereChromosomes(paired chromatids)

Centriole

CentrioleSpindle

Metaphase

Mitosis: METAPHASE

MetaphaseThe chromosomes

line up across the center of the cell aka

metaphase plate

Microtubules connect the centromeres to the fibers of the spindle.

Centriole

Spindle

Individual chromosomes

Anaphase

Mitosis: ANAPHASE

AnaphaseSister chromatids

separate into individual chromosomes.

The chromosomes move and separate into two groups.

Individualchromosomes

Nuclear envelope reforming

Telophase

Mitosis: TELOPHASE

TelophaseChromosomes gather

at opposite ends of the cell & lose their distinct shape

New nuclear envelopes forms around each cluster

Spindle breaks apart & nucleoli reappear

Cytokinesis

CYTOKINESIS

Cytokinesis Not a phase of mitosis

Cell membrane pinches in and the cytoplasm is split between the 2 cells

Each daughter cell has an identical set of duplicate chromosomes

Cytokinesis in Plants Cell plate forms midway between the divided nuclei.

Cell wallCell plate

Interphase

Prophase

Metaphase

Anaphase

Telophase

Interphase

Animal Mitosis

Plant Mitosis Interphase

Prophase

Metaphase

Anaphase

Telophase

Interphase

Cells in Mitosis

http://www.uoguelph.ca/zoology/devobio/210labs/mitosis1.html

http://web.mac.com/mrgaskell/iWeb/Science%20Extras/Mitosis%20Slides.html

Things to look:Shape of Cell & If there is a division forming between cells

Chromosomes & Location Presence of a nucleus

http://www.uoguelph.ca/zoology/devobio/210labs/mitosis1.html

http://web.mac.com/mrgaskell/iWeb/Science%20Extras/Mitosis%20Slides.html

Mitosis Animations

http://www.johnkyrk.com/mitosis.html http://www.youtube.com/watch?v=VlN7K1-9QB

0

http://outreach.mcb.harvard.edu/animations/biochem.swf

http://www.hybridmedicalanimation.com/anim_mitosis.html

http://www.biology.arizona.edu/Cell_bio/tutorials/cell_cycle/cells3.html

http://www.johnkyrk.com/mitosis.html

http://www.youtube.com/watch?v=VlN7K1-9QB0

http://www.youtube.com/watch?v=VlN7K1-9QB0







Controls on Cell Division Normal cells reproduce until they come

into contact with other cells. When cells come into contact with other

cells, they respond by not growing. This shows that cell growth and division

can be turned on and off.

Cell Cycle Regulators Regulated by a specific protein called cyclin Cyclin concentration rises and falls in time

with the cell cycleo Internal Regulators:

-Proteins responding to events inside cell- Allow the cell cycle to proceed only when

certain processes have happened inside the cell.

o External Regulators:-Proteins responding to events outside cell-direct cells to speed up/slow down the cell

cycle

Cancer: Uncontrolled Cell Growth cells lose the ability to control growth.

Cancer cells do not respond to the signals that regulate the growth of most cells.

Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues.

Metastasis-cancer cells may break loose from tumors and spread throughout the body

Cancer Cells

http://science.education.nih.gov/supplements/nih1/cancer/activities/activity2_animations.htm




Interphase

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Prophase



Metaphase



Anaphase



Telophase



Meiosis cell division by which germ cells (eggs and sperm) are produced.

One parent cell produces four daughter cells (not genetically identical)

During meiosis, DNA replicates once, but the nucleus divides twice.

Daughter cells have half the number of chromosomes (n=haploid) found in

the original parent cell (2n=diploid)

Meiosis I• Prophase 1: Each chromosome duplicates and

remains closely associated. These are called sister chromatids.

• Metaphase 1: Chromosomes align at the center of the cell.

• Anaphase 1: Chromosome pairs separate with sister chromatids remaining together.

• Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the chromosome pair.

Prophase I

http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html


Prophase I



Metaphase I



Telophase I



MEIOSIS II• Prophase 2: DNA does not replicate.

• Metaphase 2: Chromosomes line up at the center of the cell

• Anaphase 2: Centromeres divide and sister chromatids move separately to each pole

• Telophase 2: Cell division is complete

4 haploid daughter cells are formed

Prophase II


Metaphase II


Telophase II


Meiosis

http://www.biosci.uga.edu/almanac/bio_103/notes/apr_3.html.

Meiosis Animation

http://www.rothamsted.bbsrc.ac.uk/notebook/courses/guide/movie/meiosis.htm

Crossing OverA section of 1 chromosome switches places with

the same section from the other chromosome

http://www.accessexcellence.org

http://post.queensu.ca/

Differences in Mitosis & Meiosis

• Mitosis– Asexual– Cell divides once– Two daughter cells– Genetic information is

identical

• Meiosis– Sexual– Cell divides twice– Four haploid daughter

cells– Genetic information is

different

Purpose of Reproduction

• To make sure a species can continue.– Definition: Reproduction is the process by

which an organism produces others of its same kind.

Asexual Reproduction

• A new organism produced from 1 organism

• The offspring will have hereditary material uniform with the hereditary material of the parent organism. This means they will be genetically alike.

Sexual Reproduction

• Requires two sex cells – egg and sperm• The egg and sperm join to form an entirely

new organism– Different from the parent organism

IMPORTANT!

• Asexual reproduction results in offspring that are genetically identical to the parent organism

• Sexual reproduction results in offspring that are genetically different from the parent organisms-more energy so….

WHY IS IT WORTH IT?

Comparison Animations

http://www.pbs.org/wgbh/nova/baby/divi_flash.html

http://www.usoe.k12.ut.us/curr/science/sciber00/7th/genetics/sciber/animatin.htm

Documents

THE CELL CYCLE and CELL DIVISION