Human cells have 46 chromosomes.

1. Human cells have 46 chromosomes. 46 parent cell MITOSIS identical daughter cells 46 46

2. Vocabulary for mitosis: CHROMOSOME—made of many genes (each gene codes for 1 protein) --DNA is wrapped around proteins called histones When they’re tangled up and diffuse, chromosomes are called CHROMATIN.

3. 1 chromosome 1 chromosome made of 2 SISTER CHROMATIDS identical sister chromatids are held together by centromeres (kinetochores)

4. The Cell Cycle: the life of a cell (can happen once or many times in a cell’s life.)

5. Interphase—made up of G1, S, and G2 • preparation for mitosis • longest part of the cell cycle • G1 (Gap 1) • chromatin present (DNA is not replicated!) • Cell grows, makes proteins, does all the normal things a cell does.

6. S (Synthesis) • DNA and chromosomal proteins replicate • Lasts a few hours • G2 (Gap 2) • Mitotic spindle proteins are made, organelles replicate • Chromosomes begin to condense.

7. In interphase, chromosomes cannot be seen because they’re too diffuse. By the beginning of mitosis, chromosomes can be seen (at this point, they’re in the form of sister chromatids).

8. Cell division: • mitosis = division of the nucleus • cytokinesis = division of the cytoplasm • Mitosis consists of 5 phases: • prophase • prometaphase • metaphase • anaphase • telophase

9. microtubules are arranged around the centrioles in a star-like configuration  ASTER

10. Prophase: • chromosomes condense • chromosomes are now visible • nucleoli disappear • each chromosome is made of two sister chromatids • the “sisters” are held together by a centromere (kinetochore) • spindle begins to form

11. Prometaphase: • nuclear envelope fragments • centrioles move to the poles • spindle fibers extend from poles to equator • asters brace centrioles to cell membrane

12. Metaphase: • chromosomes line up on the metaphase plate • centromeres are aligned • football shaped apparatus is called the spindle

13. Anaphase: • paired centromeres separate • spindle fibers pull centromeres to opposite poles • sister chromatids separate • Kinetochore microtubules shorten • non-kinetochore microtubules lengthen

14. Telophase: • reverse of prophase! • chromosomes decondense • nuclear membrane reappears • cell membrane pinches in (in animal cells) • Cytokinesis: • division of cytoplasm • 2 NEW CELLS!!!!!!!

15. Cytokinesis in plant cells: Vesicles filled with polysaccharides form a double membrane on the metaphase plate called the CELL PLATE The cell plate becomes the cell wall during cytokinesis. cell plate

16. ANIMAL CELL PLANT CELL

17. Cell Cycle Regulation • Different kinds of cells take different amounts of time to complete the cell cycle • Some cells divide often, some rarely,and some not at all. As a cell goes through the cell cycle, there are checkpoints to tell it whether to continue.

18. 3 major checkpoints GO STOP G0

19. Important regulatory proteins are: CYCLIN-DEPENDENT KINASES (Cdk) must be attached to a protein called a cyclin, which has a fluctuating concentration in the cell proteins that phosphorylate other proteins to activate them

20. MPF = Maturation (or Mitosis) Promoting Factor =Cdk + cyclin triggers G2Mitosis

21. When there’s lots of MPF, it causes destruction of the cyclin. When there’s no cyclin, MPF is inactive.

22. M phase checkpoint: If centromeres are not attached to spindle fibers, anaphase is delayed. Once the centromeres are attached, it’s OK for anaphase to begin. (Makes sense—otherwise the daughter cells would get too many or too few chromosomes!)

23. External growth factors (from other cells) bind to receptors on cells to cause cell division. growth factor growth factor receptor GO!

24. Cancer cells don’t heed control signals STOP grow usually destroyed tumor Metastasis is the spread of cancer cells beyond their original site.