1. Cell Division

3. Mutations and Cancer
Mutation = random changes to the base sequence of genes
A mutation may change a proto-oncogene (produces normal cell cycle control)  oncogene (produces uncontrolled cell cycling)
Mutagens = agents that produce changes in genes involved in controlling the cell cycle, causing uncontrolled cell division.
Chemical (asbestos, dioxins, tobacco smoke, etc.)
X-rays or short-wave UV light
Metastasis = movement of cells from a primary tumor to set up secondary tumors in other parts of the body.

4. Mitosis
Check out onion root tips undergoing mitosis. Can you determine what phase the cell is at?
Online Onion Root Tips

5. Why cells divide? Large cells have a reduced SA:Vol ratio
Growth of organism
Replace dead, damaged or infected cells
Asexual reproduction

6. Stages of the cell cycle
interphase
G1: growth, protein synthesis, increase in the number of mitochondria and/or chloroplasts
S: DNA replication
G2: growth, protein synthesis, preparation for mitosis/cytokinesis
mitosis = nuclear division
prophase
metaphase
anaphase
telophase
cytokinesis = cellular division

7. Terms Chromosome = DNA + proteins Chromatid = one of two copies of DNA
Sister chromatids = two identical copies of DNA
Centromere = region on chromosome that joins sister chromatids
Spindle fiber = microtubules that move chromosomes during cell division
Centriole = microtubule organizing center

8. Prophase
Chromosomes condense by supercoiling, becoming visible to microscopic view
Centrioles move to opposite poles
Nucleolus disappears
Nuclear membrane disappears
Microtubular spindle apparatus forms at each pole

9. Metaphase Spindle microtubules attach to chromosome centromeres
Chromosomes move to the equator

10. Anaphase
Centromeres split as spindle microtubules pull chromatids to opposite poles (after centromeres split, sister chromatids are known as sister chromosomes)
Sister chromosomes move to opposite poles as microtubules shorten

11. Telophase Sister chromosomes have arrived at poles Spindle disappears
Centrioles replicate
Nuclear membrane reforms and becomes visible
Nucleolus becomes visible
Chromosomes decondense, becoming chromatin