2. What do all cells require to survive? A complete set of genetic instructions – to produce required molecules – to direct life processes Genetic instructions are coded in the DNA of cells

3. Why do cells divide? Growth Repair injuries Natural replacement

4. The Cell Cycle Defined as the activities of a cell from one cell division to the next, during which… – the cell grows, adding more cytoplasmic constituents – the DNA is replicated – the cell divides into two identical daughter cells

5. During non-division phase of cell cycle DNA molecules in extended, uncondensed form = chromatin – a cell can only use DNA to produce molecules when in extended state “chromatin” means colored thread

6. During division phase of cell cycle DNA molecules condense to form chromosomes prior to division – easier to sort and organize DNA into daughter cells

7. Structure of a chromosome unreplicated chromosome arm centromere “chromosome” means colored body

8. Prior to cell division: chromosomes (DNA) are replicated (duplicated) duplicated chromosome duplicated chromosome – attached at their centromeres – as long as attached, known as sister chromatids

9. Interphase “I am a cell” The cell spends a majority of it’s time in this phase. During interphase… the cell grows in size it makes copies of its organelles It makes copies of its DNA

10. Mitosis 4 phases: 1 st – Prophase 2 nd – Metaphase 3 rd – Anaphase 4 th – Telophase

11. Prophase “P is for pairs” chromosomes condensed and in pairs: 2 sister chromatids attached at the centromere spindle fibers form chromosomes are captured by the spindle fibers one pair of centrioles migrates to one pole of cell, the other pair migrates to opposite pole of cell nuclear envelope disintegrates and nucleolus disappears

12. chromatin nucleolus nucleus centrioles condensing chromosomes

13. Metaphase “M is for middle” chromosomes align along the equator (middle) of the cell centrioles spindle fibers chromosomes

14. Anaphase “A is for apart” sister chromatids separate spindle fibers attached at centromeres shorten and pull chromatids poleward

15. Telophase “T is for Two nuclei” spindle fibers disintegrate nuclear envelopes form around both groups of chromosomes making TWO nuclei chromosomes revert to chromatin nucleoli reappear

16. chromosomes decondensing nuclear envelope reforming nucleolus reappears pinching of cell membrane at equator

17. cytokinesis End of cycle – Cytokinesis – membranes finish pinching apart and cells become separate.

18. Differences in Plant cells: – stiff cell wall makes pinching impossible – Golgi complex buds off vesicles filled with carbohydrate – vesicles line up at equator and fuse, producing a structure called the cell plate – cell plate becomes new cell wall between the two cells