1. Cells have distinct phases of growth, reproduction and normal functions

2. The cell cycle has four main stages – Regular pattern of growth, DNA replication, and cell division

3. Main Stages- gap 1, synthesis, gap 2, and mitosis – Gap 1 (G₁): cell growth and normal functions – DNA synthesis (S): copies DNA – Gap 2 (G₂): additional growth – Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis) Do all cells divide at the same rate?

4. Why do you think skin cells only have a life span of about 2 weeks? Some cells divide only rarely- G₀ phase

5. Cell size is limited – Volume increases faster than surface area Which cell has the largest surface area? Which cell has the largest surface area-to-volume ratio? Which has the larger ratio of surface area to volume, a tennis ball or a soccer ball? Why is a suitable cell size important?

6. Cells divide during mitosis and cytokinesis Chromosomes condense at start of mitosis

7. DNA wraps around proteins (histones) that condense it Chromatin- DNA plus proteins Chromatid- half of a duplicated chromosome Centromere- hold sister chromatids together Telomeres- found on end of DNA molecules and protect them

8. Mitosis and cytokinesis- produce two genetically identical daughter cells Interphase prepares the cell to divide – DNA is duplicated Mitosis divides the cell’s nucleus in four phases – Prophase, Metaphase, Anaphase, Telophase Mitosis 1 video

9. Mitosis divides the cell’s nucleus in four phases – Prophase- chromosomes condense and spindle fibers form, nuclear envelope breaks down

10. Metaphase- chromosomes line up in the middle of the cell – Chromosomes are connected to spindle fiber

11. Anaphase- sister chromatids separate to opposite sides of the cell

12. Telophase- new nuclei form and chromosomes begin to uncoil – Two new nuclear envelopes will form

13. Cytokinesis- division of cytoplasm – Usually occurs at same time of telophase Cytokinesis differs in animal and plant cells – Animal- membrane pinches closed – Plant- cell plate forms Mitosis 2 Video