Cell Growth and Division

1. Cell Growth and Division

2. Breaking Down the Definitions • Cell division • Chromatid • Centromere • Interphase • Cell cycle • Mitosis • Prophase • Centriole • Spindle • Metaphase • Anaphase • Telophase • Cytokinesis • Homologous • Diplois • Haploid • Meiosis • Tetrad • Crossing-over

3. Cell Division • Before a cell becomes too large it divides and forms to DAUGHTER Cells. This process is called CELL DIVISION (or reproduction). • Cell Division Video CLip

4. The Chromosome • During cell division the cell’s DNA is coiled compactly into a CHROMOSOME • Each chromosome is a single DNA molecule • The DNA wraps tightly around a protein called HISTONE (helps maintain the chromosome’s shape)

6. Anatomy of a Chromosome • Each half of a chromosome is called a CHROMATID • Chromatids form as the DNA copies itself before cell division • The 2 Chromatids are attached at a point called a CENTROMERE • CHROMATIN=less tightly areas of DNA between cell divisions

7. Chromosome Numbers • Every species has a certain number of chromosomes in each cell. • Animal chromosomes are either: • Sex Chromosomes—will determine the gender of an organism (X and Y) • Autosomes—all of the other chromosomes • Cells with 2 sets of Chromosomes are DIPLOID • Cells with one set of chromosomes are HAPLOID (sex cells…half the number of chromosomes)

8. Chromosomes Clip • How many chromosomes does a potato have? • How many chromosomes do Ferns have? • After the video…in your own words why do different organisms have different numbers of chromosomes??

9. The Cell Cycle • The CELL CYCLE is the repeating events of the life of a cell. • Interphase is the period between cell divisions

10. Interphaseoccurs before mitosis begins • Chromosomes are copied (# doubles) • Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy(sister chromosome) change to sister chromatids at end of this phase CELL MEMBRANE Nucleus Cytoplasm

11. Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

12. Prophase 1st step in Mitosis • Mitosis begins (cell begins to divide) • Centrioles (or poles) appear and begin to move to opposite end of the cell. • Spindlefibers form between the poles. Centrioles Sister chromatids Spindle fibers

13. Prophase Plant Cell Animal Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

14. Metaphase 2nd step in Mitosis • Chromatids(or pairs of chromosomes) attach to the spindle fibers. Centrioles Spindle fibers

15. Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

16. Anaphase 3rdstep in Mitosis • Chromatids(or pairs of chromosomes) separate and begin to move to opposite ends of the cell. Centrioles Spindle fibers

17. Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

18. Telophase4th step in Mitosis • Two new nucleiform. • Chromosomes appear as chromatin (threadsrather than rods). • Mitosisends. Nuclei Nuclei Chromatin

19. Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

20. Cytokinesisoccurs after mitosis • Cell membrane moves inward to create two daughter cells – each with its own nucleuswith identical chromosomes.

21. IPMATC REMEMBER! • Interphase • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis IP___M___ A___T___ C______

22. Label it!

23. Brainpop Mitosis

24. Stages of Mitosis Animation

25. It’s your turn! Identify the stages of mitosis…

26. Mitosis Dance Video

27. Onion Tips and Whitefish…

28. Meiosis I (four phases) • Cell division that reduces the chromosome number by one-half. • four phases: a. prophase I b. metaphase I c. anaphase I d. telophase I

29. Interphase I • Similar to mitosis interphase. • Chromosomes replicate (S phase). • Each duplicated chromosome consist of two identical sister chromatids attached at their centromeres. • Centriole pairs also replicate.

30. Interphase I • Nucleus and nucleolus visible. chromatin nuclear membrane cell membrane nucleolus

31. Prophase I • Longest and most complex phase (90%). • Chromosomes condense. • Synapsis occurs: homologous chromosomes come together to form a tetrad. • Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids).

32. Crossing Over • Crossing over (variation) may occur between nonsisterchromatids • Crossing over: segments of nonsisterchromatids break and reattach to the other chromatid.

33. Tetrad nonsister chromatids chiasmata: site of crossing over Crossing Over - variation variation

34. Metaphase I • Shortest phase • Tetrads align on the metaphase plate. • INDEPENDENT ASSORTMENT OCCURS: 1. The random separation of the homologous chromosomes---this results in GENETIC VARIATION

35. OR metaphase plate metaphase plate Metaphase I

36. Anaphase I • Homologous chromosomes separate and move towards the poles. • Sister chromatids remain attached at their centromeres.

37. Anaphase I

38. Telophase I • Each pole now has haploid set of chromosomes. • Cytokinesis occurs and two haploid daughter cells are formed.

39. Telophase I

40. Meiosis II • No interphase II (or very short - no more DNA replication) • Remember: Meiosis II is similar to mitosis

41. Prophase II • same as prophase in mitosis

42. metaphase plate metaphase plate Metaphase II • same as metaphase in mitosis

43. Anaphase II • same as anaphase in mitosis • sister chromatids separate

44. Telophase II • Same as telophase in mitosis. • Nuclei form. • Cytokinesis occurs. • Remember: four haploid daughter cells produced. gametes = sperm or egg

45. Telophase II

46. Meiosis IDraw This!

47. Meiosis IIDrawThis!

48. Meiosis

50. Cells Dividing Clip