Why do Cells divide? Growth of tissue Cell repair When you get a cut, where does the “new skin” come from?

Cell Growth Rather than increase in size, cells must divide To avoid DNA “overload:” Too many chromosomes would result in mutations Keep exchange of materials through the cell membrane efficient: How fast water, food, and oxygen are transported through the cell membrane depends on size and volume of the cell

Surface Area to Volume Ratio Cells favor a large Surface Area to volume ratio The larger the surface area to volume ratio, the easier it is for the cell to transport materials in /out of the cell

Size of Cells Are adult and baby cells the same size? Yes! If mice cells are transplanted into an Elephant will they get bigger? It depends, but yes!

Controls in Cell Growth Heart & nerve cells rarely divide once they are mature Skin & digestive tract cells divide constantly to replace shedding or injured cells This is programmed by the cell cycle which is controlled by DNA

Mitosis Process in which body cells divide to produce two genetically identical (daughter) cells is known as cell division. It is asexual reproduction Somatic Cells are all body cells The only cells that do not do mitosis are sex cells produced in ovaries and testes.

Mitosis terms Body cells have a total of 46 chromosomes They are paired so we have how many pair? 23! We represent 23 PAIRS as 2n If we had a total of only 23 it would be just n We call a total of 23 pairs Diploid, 2n

Mitosis -Diagram of Chromosomes WS in packet

Mitosis terms-Diagram of key cell terms during mitosis Chromatin DNA that resembles a ball of yarn Centrioles -microtubules connect to … Centrosomes- region of microtubules Spindle Fibers -connect to chromosomes from Centrioles Poles -regions on end of cell regions. Spindle fibers connect to them Metaphase plate -area where chromosomes line up to divide Cleavage furrow -forms during Telephase. Where cytoplasm divides in the new cells. Pole

The Cell Cycle There are 3 main stages 1. Interphase, the cell prepares for division. A. 90% of the cells time is spent in this phase.

CELL GROWTH PHASE 1. INTERPHASE http://highered. mcgraw-hill Consists of 3 steps G1-The cell grows, making additional organelles & cytoplasm S-DNA replicates G2-Cell will make anything additional needed for division

The cell goes through 4 phases to reproduce a duplicate body cell MITOSIS is Stage 2 and has 4 PHASES http://bcs.whfreeman.com/thelifewire/content/chp09/0902001.html 2. Mitosis The cell goes through 4 phases to reproduce a duplicate body cell The phases are: Prophase Metaphase Anaphase Telophase

Phases of Mitosis Early Prophase Late Prophase

Creation of new cytoplasm that divides the cell into 2 new ones. Stage 3 CYTOKINESIS Creation of new cytoplasm that divides the cell into 2 new ones. Plant cell mitosis Animal cell mitosis

Cancer is a form of uncontrolled cell growth Uncontrolled Cell Growth Teacher’s Domain Cell folder how cancer grows http://www.pbs.org/wgbh/nova/cancer/grow_flash.html Cancer is a form of uncontrolled cell growth The check points that the cell goes through may no longer work If this occurs, then a tumor may form It can be non-cancerous which is called benign Or if it has spread metastasized