1. Mitosis and Cell Division Bio 11 August 31, 2007

2. Cells are extremely small Size limit of cells determined by area/volume ratio Large living things are made of multiple cells Living things divide cells in order to grow

3. Living things are extremely complex Cellular machinery is sophisticated and required for life Blueprints for all cellular machinery are contained in genes Genes are inherited from parents Humans have ~30,000 genes

4. All cells require a copy of the genome Genome- all the DNA of the cell Gene- the genetic information to produce a single product (protein) DNA replication copies all cellular DNA

5. Prokaryotic genomes consist of a single circular chromsome Chromosome- a single molecule of DNA

6. Prokaryotic cells reproduce by binary fission 1.DNA is copied 2.Copies migrate to opposite ends of cell 3.Cell membrane/cell wall pinches off to form two cells 4.Each daughter cell has exactly the same DNA as the parent cell

7. Eukaryotic cells have multiple linear chromosomes Eukaryotic chromosome = DNA + extra proteins Chromosomal proteins assist in DNA compaction Each chromosome contains different genes Chromosomes not always condensed like this Chromatin – uncondensed chromosomal DNA

8. Eukaryotic chromsomes are generally found in pairs Chromosomes are organized and numbered by size Humans: 2 x 23 homologous pairs of chromosomes = 46 total chromosomes

9. Chromosome structure Decondensed chromosome- chromatin After copying, chromosome consists of two sister chromatids, joined at the centromere Kinetochore – proteins found on surface of centromere

10. Each chromosome must be copied before cells can divide Called “chromosome” at all stage Sister chromatids contain identical DNA

11. Mitosis vs. Meiosis Mitosis – asexual cellular reproduction (somatic cells) –Allows multicellular organisms to grow –Daughter cells are identical to parent cell Meiosis – cell division for formation of gametes (eggs and sperm) –Allows sexual reproduction to generate species diversity –Daughter cells have half the genetic information as parent cell

12. The Cell Cycle G1 – “Growth 1” or “Gap 1” – cell growth S phase – DNA synthesis G2 – interval of rest before cell division M – mitosis Cytokinesis – splitting of cell contents G O – A state of non- division

13. LE 8-5 I NTERPHASE G1G1 G2G2 S (DNA synthesis) Cytokinesis Mitosis M ITOTIC PHASE (M)

14. Mitosis The sorting and separation of chromosomes in nucleus somatic eukaryotic cells during cell division Forms 2 identical daughter cells (1/2 size) For growth/replacement/healing Associated with cancer In humans: ~25 million/sec. Divided into phases

15. Phases of Mitosis Prophase* Metaphase Anaphase Telophase * Campbell text adds “prometaphase” Interphase – time in between mitotic phases –Normal cell functions (G1+S+G2) Cytokinesis- divides cytosol/organelles (creates daughter cells)

16. Peripheral elements of Mitosis Centrosomes (2) – form spindle fibers, and consist (in animal cells) of 2 centrioles Spindle fibers – made of microtubules, they pull apart sister chromatids of chromosomes

17. LE 8-6a I NTERPHASE P ROPHASE P ROMETAPHASE Kinetochore Fragments of nuclear envelope Centrosome Early mitotic spindle Chromatin Centrosomes (with centriole pairs) LM 250  Nucleolus Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Centromere Spindle microtubules

18. LE 8-6b M ETAPHASE A NAPHASETELOPHASE AND C YTOKINESIS Metaphase plate Spindle Daughter chromosomes Nuclear envelope forming Cleavage furrow Nucleolus forming

19. Cytokinesis in animal cells is different from plant cells Actin and myosin filaments work to contract cell in center Cell furrow is formed

20. Plant cell walls aren’t flexible Vesicles containing cellulose form in center of cell Fusion of vesicles forms cell plate Cell plate forms cell wall of new cells

21. Control of the mitotic cycle is critical G 1 checkpoint G0G0 G1G1 G2G2 G 2 checkpoint M checkpoint M S Control system

22. External signals can activate or deactivate the cell cycle Signals include hormones, growth factors Contact inhibition, density inhibition, anchorage dependence are important signals

23. LE 8-8a Cells anchor to dish surface and divide. When cells have formed a complete single layer, they stop dividing (density-dependent Inhibition). If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).

24. LE 8-8aa Cells anchor to dish surface and divide. When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).

25. LE 8-8ab If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).

26. LE 8-8b After forming a single layer, cells have stopped dividing. Providing an additional supply of growth factors stimulates further cell division.

27. LE 8-10 Tumor Glandular tissue Lymph vessels Blood vessel A tumor grows from a single cancer cell. Cancer cells invade Neighboring tissue. Cancer cells spread through lymph and blood vessels to other parts of the body.

28. LE 8-10a Tumor Glandular tissue A tumor grows from a single cancer cell. Cancer cells invade neighboring tissue.

29. LE 8-10b Cancer cells invade neighboring tissue. Cancer cells spread through lymph and blood vessels to other parts of the body. Lymph vessels Blood vessel

30. Figure 8.11A

31. Figure 8.11B

32. Figure 8.11C

33. LE 8-12 Chromosomes Centromere Sister chromatids

34. LE 8-13 Haploid gametes (n  23) Egg cell Sperm cell FertilizationMeiosis Diploid zygote (2n  46) n Multicellular diploid adults (2n  46) Mitosis and development 2n n

35. LE 8-14a I NTERPHASE P ROPHASE  M ETAPHASE  A NAPHASE  M EIOSIS  Centrosomes (with centriole pairs) Sites of crossing over Spindle Microtubules attached to kinetochore Metaphase plate Sister chromatids remain attached Homologous chromosomes separate Centromere (with kinetochore) Tetrad Sister chromatids Chromatin Nuclear envelope : Homologous chromosome separate

36. LE 8-14b Cleavage furrow T ELOPHASE  P ROPHASE  M ETAPHASE  A NAPHASE  T ELOPHASE  Sister chromatids separate Haploid daughter cells forming M EIOSIS  : Sister chromatids separate  AND C YTOKINESIS