CELL CYCLE Cell Division

cancer  /cancer/activities/activity2_animations.htm

Strawberry Division!

Why do cells need to divide?  Growth – so organisms can increase in size (natural selection theory)  Development – for cells to become specialized (e.g. create organs)  Repair – for cells to replace removed or dead cells (e.g skin cells)

Which cells divide the most?  Skin cells are dividing all day, everyday.  We lose around 30,000 to 40,000 skin cells a minute!  That’s 50 million skin cells lost in one day!

Cell Cycle – Somatic Cells  Interphase – cell growth takes place Inter = enter  Mitosis – division of DNA(chromosomes) mito = strong, powerful sis = process  Cytokinesis – division of cytoplasm cyto = cell kinesis = movement

What is the 1 st part of the cell cycle? Interphase  G1 (growth stage one) : cell is growing & developing and making proteins  S (synthesis): DNA replication process  G2 (growth stage two): cell is making final preparations for cell division

Cell Cycle

Closer look at “S phase”

What is the 2 nd part of the cell cycle? Mitosis  Prophase  Metaphase  Anaphase  Telophase/Cytokinesis

Mitosis  Prophase -chromatin begins to coil into think, visible chromosomes

Mitosis  Metaphase -spindles fibers line up chromosomes in the “middle”

Mitosis  Anaphase -spindle fibers move chromosomes “apart”

Mitosis  Telophase -chromosomes reach opposite ends -centromere

Cytokinesis Animal CellPlant Cell

Cytokinesis: Which cell is pictured?

What happens if the cycle is disrupted?  Cancer is uncontrolled cell division or inappropriate cell proliferation  Cascade of chemical reactions that relay a cell from one stage to the next  Set of checkpoints that monitor completion of critical events and delay progression to the next stage, if necessary  Genetic alterations shown to contribute to cancer development  Gain-of-function mutations (oncogenes)  Loss of function  mutations (“tumor suppressor” genes)

Independent Activity In ten minutes, you will be able to write 6 sentences using the following words:  Interphase  Prophase  Metaphase  Anaphase  Telophase  Cytokinesis