Since cells can’t continue to grow larger, they must split, or divide at some point.

1. Since cells can’t continue to grow larger, they must split, or divide at some point.

2. Cell Cycle 2 parts: • Interphase – period of growth & DNA synthesis (copying) • Mitotic phase – period of cell division (1 cell divides into 2 cells) I love cells, baby!

3. Interphase – time of cell growth & copying of DNA 3 phases of interphase: • G1 – growing & ribosomes making proteins • S – synthesis (or copying) of DNA (sister chromatids formed) • G2 – growing & getting ready to divide

4. Cells spend most of their time in interphase.DNA is in chromatin (stringy) form.

6. Mitotic Phase – time of cell division Consists of 2 main phases: • Mitosis – division of nucleus • Cytokinesis – division of cytoplasm

7. Sister Chromatids • Identical copies of chromosomes attached by a centromere.

10. Mitosis 4 phases: • Prophase • Metaphase • Anaphase • Telophase http://www.cellsalive.com/mitosis.htm

11. Prophase • DNA condenses into chromosomes • Nuclear membrane disappears • Centrioles move toward poles • Spindle fibers form & attach to chromosomes

12. Metaphase • Sister chromatids lined up on metaphase plate with spindle fibers attached to them.

13. Anaphase • Sister chromatids get pulled apart to poles as spindle fibers shorten.

14. Telophase • New nuclear membrane forms around chromosomes at each pole • Chromosomes “unpack” into chromatin • Cell membrane begins to pinch in (animals cells) or cell plate develops (plant cells)

15. Cytokinesis – division of the cytoplasm Cell plate Cleavage furrow

18. Control of the Cell Cycle • Enzymes control cell cycle so cells divide at the right times • Cancer – uncontrolled cell division caused by a change in the DNA that codes for the making of the control enzymes

19. Cell Cycle Control • http://wps.prenhall.com/esm_freeman_biosci_1/7/1948/498717.cw/index.html

20. Internal Vs external signals • Internal – the checkpoints • External – growth factors, density dependent inhibition, anchorage dependence

21. Cell cycle checkpoints • length varies depending on cell type cell cycle checkpoints control the cell’s progression. Check points determine if a cell is ready to progress to the next stage. G1 – mostly controlled by growth factors G2 - determines if cell will enter the M phase & requires proper completion of DNA synthesis. M - b/t metaphase & anaphase; requires the proper attachment of all chromosomes to spindle apparatus.

22. MPF = mitotic cyclin dependent kinase complex

23. How MPFs work to control the cell cycle Once bound to cyclin, the mitotic cyclindepdendentkinase complex (or MPF) phosphorylates proteins involved in the early stages of mitosis. The active MPF stimulates the following: • breakdown of the nuclear envelope • chromosome condensation, • mitotic spindle formation • degradation of key proteins. • activating the anaphase promoting complex

24. To sum up… • CDKs are only active when bound to cyclin. • When working, they cause the cell to go through the mechanics of mitosis. • The cell doesn’t continually go through mitosis b/c the cyclin gets destroyed when the MPF complex reaches a certain concentration.

25. cancer • Tumor • Begign • Malignant • Metastasis • Radiation & chemo

26. Cancer • Forms tumors & can spread through body - metastasize

27. Causes of Cancer • Environmental factors • UV radiation from sun • Tobacco • Viral infections • Genetic

28. How to prevent cancer: • Low fat, high fiber diet • Vitamins • Exercise • Don’t smoke • Use sunscreen • Regular doctor appointments

29. Removal of colon polyps • http://www.gihealth.com/flashvideo/flash.html

30. Review of the cell cycle • http://www.cellsalive.com/mitosis.htm

31. 2 Basic Modes of Reproduction: • Asexual – one parent • Produces offspring ID to parent • Ex: sponges, some worms, some plants, bacteria, some fungi • Variation occurs through mutation • Sexual – two parents • Genetic variation occurs

32. Meiosis • The making of gametes • Reduces chromosome # by ½ so the 2 halves can come together & make a whole. • Creates genetic variation.

33. Terms you need to know: • Somatic cell – all cells other than sperm & egg. Humans = 46 chromosomes; diploid ( 2n) • Gametes – sperm & egg. Humans = 23 haploid (n) • Gene – seg of DNA that codes for the making of a polypeptide

34. Karyotype • An ordered picture of an individuals chromosomes used to detect abnormal chromosome #

35. Trisomy 21 karyotype

36. More terms you need to know: • Homologous chromosomes – paired chromosomes that contain genes that code for the same traits.

37. Homologous Chromosomes

38. Meiosis has 2 parts: • Meiosis produces 4 non – identical haploid gametes. • Meiosis I – separates homologous pairs of chromosomes. • Meiosis II – separates sister chromatids – just like mitosis. • http://www.cellsalive.com/meiosis.htm

39. Meiosis I & II

40. 2 Notable events in meiosis I that cause genetic variation in gametes: • Random assortment of homologous chromosomes - there are 2 possible arrangement of maternal & paternal chromosomes on the metaphase plate. 2n – humans = 8 million possible combinations

41. 2 Notable events in meiosis I that cause genetic variation in gametes … 2. Crossing over – occurs when nonsister chromatids of homologous chromosomes exchange genes. Can happen at up to 3 different locations along the pair. http://www.csuchico.edu/~jbell/Biol207/animations/recombination.html

42. A third notable event that causes variation in offspring, not gametes, & occurs after meiosis if sperm & egg meet: • Random fertilizaiton – chance determines which sperm (all of which are different) fertilizes which egg (all of which are different).

43. Meiosis & Mitosis compared: • http://www.pbs.org/wgbh/nova/baby/divi_flash.html

44. Mistakes in Meiosis • Nondisjunction – when chromosomes don’t separate during meiosis. • Results in: • Trisomy – 3 of a chromosome • Ex: Down Syndrome • Ex: Klinefeltersyndromexxy • Monosomy – 1 of a particular chromosome • Ex: Turner syn http://www.tokyo-med.ac.jp/genet/anm/domov.gif

45. Trisomy 21

46. Some terms • Autosomes – chromosomes other than the sex chromosomes • Tetrad • synapsis • chiasmata

47. Evolutionary adaptation depends on a population’s genetic variation. • Those individuals best adapted to their env will live longer & therefore reproduce more, passing on their well adapted genes. • More variation means a greater chance of individuals being better adapted, allowing for the survival of the species.