A Top of Class production

What is the Cell Cycle?  Series of events  Cell growth  Cell division  Produce two daughter cells  Each new daughter cell will then enter into its own “new” cell cycle  Growth and division  Prokaryotic vs. Eukaryotic

Prokaryotic Cycle  No definable nucleus  One DNA loop  Enters regular cycle  Growth, DNA replication, and cell division  Ideal conditions…very quick

When to divide?

Eukaryotic Cycle  Cycle has four phases  Phase lengths vary  Cell type  Liver Cells…1-2 a year  Bone cells…6-8 weeks  Skin cells…6-10 days  Brain cells…never  Divisions are separated by “in-between” time  This is not a resting period  Much happens!

The “Cell cycle” accounts for all things that a cell does during its life span… What are those things? 1. G 0 2. G 1 3. G 2 4. S 5. M 6. Cytokinesis

Interphase - “between” phase  G1 Phase  Cell Growth…majority of size increase  new proteins and organelles  G = gap phase  S Phase  DNA Replication…copy of DNA made  Ends with twice the amount of DNA  S = synthesis

Interphase continued…  G2 Phase  Cell growth…prep for cell division  Shortest phase  Materials for division are made  During the first three stages the cell grows and prepares for _____________?

M Phase  Cell Division  Production of two daughter cells  Faster than interphase  Two stages  MITOSIS  CYTOKINESIS  Both stages can overlap

G 0 The Resting Period A cell will leave the cycle and quit dividing. Temporary Permanent Example… A cell that has reached an end stage of development and will no longer divide Neuron

Restrictive Point  Passage through the restriction point is controlled by cyclin dependent kinases (CDKs)  Looking for damage  If found, the checkpoint uses a signal mechanism  stall the cell cycle until repairs are made  if repairs cannot be made; then target the cell for destruction via apoptosis

Why do we care about the cell cycle?  Cells split  Cells grow  Making DNA copies  We must replace other cells.  If we don’t replace we die and have tissue/organ degeneration  If a cell is replaced before it needs to be……?