Cellular ReproductionChapter 9

http://www.carolina.com/product/life+science/dvds+and+videos/basics+of+genetics-+cellular+reproduction-+mitosis,+cytokinesis,+and+the+cell+cycle+dvd.do#

Cellular Growth9.1

Cell Differentiation• Multicellular organisms develop

beginning with a single cell (fertilized egg).

• This single cell will give rise to many different types of cells, each with a specialized structure and function.

• This is done through the process of cell division.

Cell Differentiation

• As cells undergo cell division, they not only grow in number, but they also undergo differentiation.

• The various types of cells arrange into tissues --> organs --> organ systems --> organism.

Cell Differentiation• Nearly all cells in a multicellular organism

have exactly the same chromosomes and DNA.

• When cells differentiate, only specific parts of the DNA are activated.

• This will determine the function and specialized structure of a cell.

• All cells essentially contain the same DNA, therefore they have the potential to become any type of cell.

Stem Cells• Unspecialized cells that continually

reproduce themselves and have the ability to differentiate into one or more types of specialized cells.

• Embryonic Stem Cells: have not yet differentiated into various cell types. Have the capability of developing into a wide variety of specialized cells.

• Adult Stem Cells: found in various tissues in the body and might be used to maintain and repair the same kind of tissue where they are found.

Stem Cells

http://www.biocat.com/cgi-bin/page/sub2.pl?sub1=stem_cell_related_products&sub2=stem_cell_differentiation_reporter_system&main_group=cell_biology

Cell Size Limitations

• Higher ratio of surface area to volume means that cells can:

• Efficiently supply nutrients and expel waste products.

• Maximize the ability of diffusion and motor proteins to transport nutrients and waste products.

• Efficiently move signaling proteins throughout the cell.

Cell Size Limitations

https://youngbloodbiology.wikispaces.com/A+Panoramic+View+of+the+Cell

The Cell Cycle

http://ehumanbiofield.wikispaces.com/MA+Cell+division+hw

The Cell Cycle

• A repeated pattern of growth and division.

• For every complete cycle, 2 cells will be produced.

• Repeated cycling results in a continuous production of new cells.

• The duration of the cell cycle varies.

The Cell Cycle

• Three main stages:

• 1) Interphase

• 2) Mitosis

• 3) Cytokinesis

The Cell Cycle:Interphase

• Majority of cycle spent in interphase.

• Cells grow, develop into mature, functioning cells, duplicate DNA, and prepare for division.

• Divided into 3 stages:

• 1) Gap 1 (G1)

• 2) Synthesis (S)

• 3) Gap 2 (G2)

The Cell Cycle:Interphase

http://www.revisionworld.co.uk/a2-us-grades-11-12/biology/genes-genetic-engineering/cell-cycle

The Cell Cycle:Interphase

• Gap 1 (G1): period immediately after cell divides. Cell is growing and carrying out normal cell functions. Prepares to replicate DNA, synthesizes proteins.

• Synthesis (S): period when the cell copies its DNA to prepare for cell division. Chromosomes replicate and divide to form sister chromatids.

• Gap 2 (G2): period when the cell prepares for division of its nucleus. The cell makes sure it is ready to continue with mitosis at this time.

The Cell Cycle:Interphase

http://www.macroevolution.net/sister-chromatids.html#.Tn_ywXN7f_E

The Cell Cycle:Mitosis

• Purpose: Cell Division (making two cells out of one)

• The cells nuclear material divides and separates into opposite ends of the cell.

• Each cell has to have its own cytoplasm and DNA.

• Divided into 4 phases (prophase, metaphase, anaphase, telophase).

The Cell Cycle:Cytokinesis

• The cell divides into 2 daughter cells with identical nuclei.

• Animal Cells: cleavage furrow forms from cell membrane, pinches the cell into 2 equal parts.

• Plant Cells: cell plate forms between the divided nuclei, gradually develops into a separate membrane.

The Cell Cycle:Mitosis/Cytokinesis

http://169.204.146.130/pauly/Life%20Science%20Web/Projects/Mitosis%20Resources%20for%20project.htm

Prokaryotic Cell Division

• Prokaryotic cells reproduce by a method called binary fission.

http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookmito.html

Mitosis and Cytokinesis9.2

Mitosis/Cytokinesis

• Mitosis: the process of nuclear division.

• Cytokinesis: the process of cytoplasm division.

Mitosis

• The cell’s replicated genetic material separates and the cell prepares to split into two cells.

• Enables the cell’s genetic information to pass into the new cells, resulting in two daughter cells that are genetically identical.

Mitosis

• Increases the number of cells as a young organism grows to its adult size.

• Replaces damaged cells.

The Stages of Mitosis

http://www.biology.iupui.edu/biocourses/N100/2k4ch8mitosisnotes.html

Mitosis: Prophase

• The cell’s chromatin condenses into chromosomes (shaped like an X).

• Each half of the X is called a sister chromatid. These contain identical copies of DNA.

• Sister chromatids are attached in the center by the centromere.

Mitosis: Prophase• The nucleolus and nuclear envelope will

disappear.

• The spindle apparatus forms. It is important in moving and organizing the chromosomes.

• Spindle apparatus: spindle fibers, centrioles, and aster fibers.

• Spindle fibers attach to the sister chromatids and attach to the centrioles at opposite ends of the cell.

Mitosis: Prophase

http://www.riaxin.com/celldiv.htm

Mitosis: Metaphase

• The sister chromatids are pulled along the spindle apparatus toward the center of the cell.

• The sister chromatids line up in the middle of the cell (equator).

Mitosis: Metaphase

http://www.riaxin.com/celldiv.htm

Mitosis: Anaphase

• The chromatids are pulled apart because the microtubules of the spindle apparatus begin to shorten.

• Shortening pulls at the centromere of the sister chromatids causing them to separate into identical chromosomes.

Mitosis: Anaphase

http://www.riaxin.com/celldiv.htm

Mitosis: Telophase

• Chromosomes arrive at the poles of the cell.

• Nuclear membrane begins to form around chromosomes at each pole and the nucleoli begin to reform.

• The spindle apparatus disassembles.

Mitosis: Telophase

http://www.riaxin.com/celldiv.htm

Cytokinesis• Divides the cytoplasm resulting in

two cells with identical nuclei.

• Animal Cells: cleavage furrow forms from cell membrane, pinches the cell into 2 equal parts.

• Plant Cells: cell plate forms between the divided nuclei, gradually develops into a separate membrane.

Cytokinesis

http://www.riaxin.com/celldiv.htm

Mitosis/Cytokinesis

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

Cell Cycle Regulation9.3

Cell Cycle Control• The timing and rate of cell division

are important to the health of an organism.

• The cell cycle is driven by a chemical control system that both triggers and coordinates key events.

• This control system is regulated at certain checkpoints.

Cell Cycle Control

• Signals from inside the cell (internal signals) and from outside the cell (external signals) are involved in turning the process of cell division off and on.

Cell Cycle Control

• An internal signal involves the cell sensing the presence of enzymes produced inside the cell.

• An external signal involves the cell sensing the presence of chemicals which were produced in other specialized cells (growth factor).

Cell Cycle Control

• Cells can also respond to physical signals from their environment.

• If the cells are too closely packed, cell division will be turned off.

• If the cell senses it is not in contact with a surface, cell division will be turned on.

Normal Cell Cycle

• The cell cycle in eukaryotes is driven by proteins called cyclins that bind with enzymes called cyclin-dependent kinases (CDK’s).

• Different combinations of cyclin/CDK control different activities at different stages in the cell cycle.

Normal Cell Cycle

• G1 stage of interphase: combination of cyclin with CDK signals the start of the cell cycle.

• CDK and cyclin combinations also signal DNA replication, protein synthesis, and nuclear division throughout the cel cycle.

• These same combinations also signal the end of the cell cycle.

http://www.ncbi.nlm.nih.gov/books/NBK21238/

Control Checkpoints

• Stop and go signals regulate the cycle.

• Ex) Checkpoint near end of G1 stage monitors for DNA damage and can stop the cycle from entering the S stage.

Control Checkpoints

• Other checkpoints include those during the S stage and after DNA replication in the G2 stage.

• During mitosis, if a spindle fiber failure is detected the cycle can be stopped before cytokinesis.

http://www.ncbi.nlm.nih.gov/books/NBK26824/

Abnormal Cell Cycle• When cells do not respond to the

normal cell cycle control mechanisms, cancer can result.

• Cancer: uncontrolled growth and division of cells.

• If left unchecked, cancer can kill an organism by crowding out normal cells, resulting in tissue failure.

• Cancer cells will divide as long as they are supplied with essential nutrients.

Abnormal Cell Cycle

• Malignant Tumor: a mass of cancerous cells that invades and impairs the functions of one or more organs.

• Benign Tumor: a mass of abnormal cells that remains at the original site.

Abnormal Cell Cycle

Abnormal Cell Cycle

• http://www.cancerquest.org/cancer-biology-animations.html