Mitosis and Interphase The Cell Cycle Mitosis and Interphase

All living things.. ..begin life as a single fertilized cell. Humans begin as a cell that results from the combination of an OVUM or human egg cell and a SPERM cell... Together they form an EMBRYO.

The embryo… ….then begins to divide into exact duplicate “stem cells”. these first cells will be the basis for all future cells in the human body. ---->note the number of cells at each step

This little batch of cells… …will not stay the same. Cells specialize and take on different jobs. ---------->at 5-6 weeks the embryo has animal-like features including a fully functional heart.

How does this work? Let’s go back to this little batch of 8 cells… We will now look at cells when they are dividing…and when they aren’t!

The Cell Cycle The steps that prepare and lead up to cell division.

Interphase The time between cell division Cell is doing its job Genetic material is all unraveled as chromatin The time between cell division Cell is doing its job DNA duplicates-chromosomes make exact copies of themselves Nuclear membrane clearly in place

Mitosis Cell divides to form two identical cells Can look at 7 different stages: Interphase Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis

Prophase DNA condenses to form distinct chromosomes Nuclear membrane begins to break down. Centrioles appear from centrosomes (microtubule organizing center) and begin to form spindle fibers.

Prometaphase Nuclear membrane breaks down. Proteins attach to centromeres to form kinetichores (eventually will attach to spindle fibers) Chromosomes move to center of cell along microtubules..

Metaphase Chromosomes line up in the middle (equator) of the cell Spindle fibers attach

Anaphase Chromosomes separate and move toward the opposite ends of the cell (poles)

Telophase Chromosomes reach the poles New nuclear membrane forms Chromosomes unwind to become thread-like chromatin again

Cytokinesis (End of Telophase) The cytoplasm is evenly divided New cell membrane forms in animal cells New cell wall is built across for plant cells

VIDEOS Drosophila Embryo - http://www.youtube.com/watch?v=m73i1Zk8EA0 Blood Lily - http://www.youtube.com/watch?v=0oJZDKdperU

Recap

Interphase/early prophase

Prophase

Metaphase

Anaphase

Telophase

OK, fine…but who really cares about MITOSIS and cell division???

Nerve cells… …remain in INTERPHASE for long periods of time. They go through mitosis about once every 75 years. So?…

Damage to these cells… …is often very serious.

Some damage is not permanent Gloria Estefan was involved in a tragic tour bus accident. Surgeons were able to repair her nearly severed spinal chord. She recently donated $1,000,000 for spinal cord injury research---->

Cancer cells… …behave much differently than nerve cells. …spend very little time in interphase and go through mitosis uncontrollably. What does that mean? Approx. 1/10,000 of your cells are cancerous but your immune system usually kill them rapidly— http://www.youtube.com/watch?v=Hm03rCUODqg&feature=fvwrel