2. Regents Biology Cell Cycle – Interphase + Mitosis  Interphase – where the cell spends most of its time  G1, S, G2  Doing GRRSNERT  Mitosis – cell division  PMAT  Making new cells  Making new DNA IPMAT

3. Regents Biology  Going from egg to baby…. the original fertilized egg has to divide… and divide… Getting from there to here… Fertilized egg = zygote Levels of organization: cells tissues organs organ systems

4. Regents Biology Why do cells divide…  One-celled organisms for reproduction  asexual reproduction (clones) – binary fission  Examples: paramecia, amoeba  Multi-celled organisms  for growth & development  from fertilized egg to adult  for repair & replacement  replace cells that die from normal wear & tear or from injury Cells MUST remain small to be efficient amoeba starfish Regeneration – part of an organism

5. Regents Biology In Dividing cells…  What has to be copied  DNA - instructions to make proteins  organelles  cell membrane - made of lipids and proteins  lots of other molecules  Enzymes –  Type of protein animal cellplant cell

6. Regents Biology Forms of DNA  Chromatin  Chromosomes  Chromatids 4 single-stranded chromosomes Unwound DNA DNA wound or coiled Replicated DNA – held together by centromeres 2 chromosomes – count centromeres 4 chromatids

7. Regents Biology DNA must be duplicated… nucleus cell DNA in chromosomes nucleus cell duplicated chromosomes Start with 2n OR diploid chromosomes Two of each “kind” – pairs of homologous chromosomes Carry similar information STILL have 2n or diploid chromosomes – but have chromatid copies # chromosomes = # centromeres

8. Regents Biology  Same size and shape  Similar “banding pattern”  In sexual reproduction – one from each pair comes from each parent Homologous Chromosomes - Pairs of chromosomes that carry similar genetic info

9. Regents Biology Before Mitosis: Interphase  G1/S/G2: cell copies DNA, makes organelles, GRRSNERT  MOST time spent in this phase doing the cell’s “job” nucleus One 2n diploid cell DNA (Chromatin) Copy DNA! (interphase)

10. Regents Biology Mitosis: PROPHASE  Prophase: DNA winds into chromosomes  DNA is wound up into chromosomes to keep it organized so they are visible  Nuclear membrane starts to break down nucleus one 2n diploid cell duplicated chromosomes Wind up! (prophase)

11. Regents Biology Mitosis: METAPHASE  Metaphase: chromosomes line up in middle  Along the “equator”  attached to protein “spindles” that will help them move to opposite “poles” Line up! (metaphase) Spindle fibers Poles – centrioles in animal cells; asters in plant cells

12. Regents Biology Mitosis: ANAPHASE  Anaphase: Chromatids separate  centromeres duplicate, homologous chromatids split, separating chromatids  start moving to opposite ends or poles Separate! (anaphase)

13. Regents Biology Mitosis: TELOPHASE (including cytokinesis)  Telophase: Cell starts to divide  nuclei form again in two new cells  Followed by cytokinesis – division of cytoplasm  animal cell membrane “pinches” in  plant cell forms a cell plate that becomes the cell wall Divide! (telophase)

14. Regents Biology Interphase (again)  DNA unwinds; cells separate  now they can go back to doing their every day jobs - GRRSNERT  cycle starts over again two 2n diploid cells 2 new smaller “daughter” cells  Get 2 exact copies of original cells  same DNA  “clones”

15. Regents Biology Mitosis in whitefish embryo

16. Regents Biology Mitosis in plant cell

17. Regents Biology onion root tip

18. Regents Biology

20. Overview of Cell Cycle interphase prophase metaphaseanaphasetelophase cytokinesis I.P.M.A.T.C. P lease M ake A nother T wo C ells

21. Regents Biology When is mitosis a BAD thing  When cells reproduce & they are not needed  these cells take over organs, but don’t do the right job  they just keep making copies  “starve” other cells/tissues  cancer – uncontrolled mitosis  damages organs

22. Regents Biology Why would cells just make copies?  If DNA gets damaged, cells stop listening to correct instructions – make WRONG protein (enzymes)  mutations – changes in DNA bases  Mutagens (carcinogens) – cause mutations:  UV radiation  chemical exposure  benzene, toluene, asbestos  radiation exposure  cigarette smoke  pollution  age  Genetics  heat

23. Regents Biology Tumors  Benign tumor  abnormal cells remain at original site as a lump  most do not cause serious problems & can be removed by surgery

24. Regents Biology Tumors  Malignant tumor  cells leave original site - metastasizes  carried by blood system to other tissues  start more tumors  damage functions of organs throughout body

25. Regents Biology Treatments for cancers  Treatments kill rapidly dividing cells  chemotherapy  poisonous drugs that kill rapidly dividing cells  radiation  high energy beam kills rapidly dividing cells  surgery side effects