Where Do Cells Come From?

1. Where Do Cells Come From? “All cells come from pre-existing cells” -Cell Theory • 3 types of cell divisions: • Mitosis-nuclear cell division in somatic cells, asexual reproduction • Meiosis-nuclear cell division in germ cells, sexual reproduction • Prokaryotic Fission-cell division in bacteria cells, asexual reproduction

2. Review of Terms used in Mitosis/Meiosis • Somatic cells-all cells except sex cells • Germ cells-sex cells, sperm and eggs • Diploid-2 of every chromosome • Haploid-1 of each chromosome • Chromosome-a linear arrangement of genes, composed of DNA • How many chromosomes are found in humans? • Which cells are diploid and haploid in humans?

3. Review of Terms used in Mitosis/Meiosis • Chromatid-1 arm of duplicated chromosome, sister chromatids • Centromere-area on chromosome that holds chromatids together • Histones-proteins associated with chromosomes, organize structure • Nucleosome-1 unit of DNA + 8 histones • Chromatin-all DNA + histones + other proteins

4. Eukaryotic Cell Cycle • Interphase-3 phases • G1-initial growth, G0 resting phase, permanently arrested • S-synthesis, DNA is duplicated • G2-final preparations before mitosis, microtubule formation • Mitosis-4 phases: Prophase, Metaphase, Anaphase, Telophase • Cytokinesis-division of cytoplasm Most adult cells are in what phase of the cell cycle?

5. Control of the Cell Cycle • Tightly regulated, require signals • Cyclins required for cells to move from G1S, G2M • In mammalian cells p53 stops cycle if DNA is damaged, hasn’t finished replicating, or if chromosomes are not attached to spindle • High levels result in apoptosis  programmed cell death through caspases

6. Mitosis • Produces 2 identical diploid daughter cells from 1 parent cell • Have the same DNA  clones • Used for growth and repair • Asexual reproduction used by some members of fungi, plants, animals, protists

7. Mitosis-PMAT Prophase • Chromosomes condense • Nucleolus disappears, nuclear envelope breaks apart • Centrioles duplicate, move to opposite poles • Microtubules grab chromosomes in order to move them • Longest phase

8. Mitosis-PMAT • Metaphase-microtubules align chromosomes at the equator of a cell, “metaphase plate” • Kinetochore spindle fibers attached to sister chromatids come from poles

9. Mitosis-PMAT • Anaphase-pulling apart of chromatids/centromeres, microtubules contract, moving chromatids to opposite poles, “spindle apparatus” is clearly visible • Shortest phase • Telophase-chromosomes decondense, nuclear envelope reforms, nucleolus reappears

10. Cytokinesis • Division of cytoplasm • Occurring simultaneously with telophase • Occurs differently in plant and animal cells • Cell plate formation-Plant cells • Vesicles from golgi align at equator and fuse to form cell wall • Cleavage Furrowing-Animal Cells • Actin filaments align at equator (contratile ring)and contract until separate cell into two

11. Stem Cells and Cloning • Stem cells adult cells that retain ability to divide • Can differentiate into different types of cells • Therapeutic cloning  produces human tissues • Reproductive cloning  new individual can be made

12. Cloning and Embryonic Stem Cells • Embryonic Stem Cells (ES)-cells from an early embryo; these cells have not received the genetic instructions to become a specialized cell yet • These cells can be transferred into a organ and become that type of tissue. Example: ES cells  defective pancreas, become pancreas cells and start producing insulin

13. Stem Cell Lines • 100s have already been created that are heart, liver, pancreas, etc. cell lines • Eventually, transplant into humans; mice studies are very promising Problems: • immune reaction • Getting the cells to defective tissue • Ethical issues (no fertilized egg required)

14. Properties of Cancer Cells: loss of cell cycle control(When Compared to Normal Cells) • Additional chromosomes, genes • Grow and divide abnormally (faster) • Less adhesive, don’t stick to each other • Metastasize-migrate to other locations • Don’t communicate with each other • Don’t apoptose (die)

15. Cancer • Unregulated and uncontrolled cellular growth • Form tumors • Metastasize

16. Cancer: Loss of Genetic Controls over Cells • Cell growth and repair is tightly regulated by genes; when these genes fail  Cancer • Proto-oncogene (accelerator) normal growth gene becomes mutated  oncogene, BRCA1 • Tumor suppressor genes (brakes) -control cell death, ex. p53 gene

17. Causes of Cancer • UV, X-ray, gamma radiation, chemicals in work places, smoking • Viruses  Hepatitis C,  liver cancer, HPV  genital warts cervical cancer • Chromosome translocation leukemia • Carcinogens-cancer causing agents, ex. Compounds found in cigarettes

18. Cancer : Tumors and Treatment • Benign-slow growth, no metastasis, not lethal unless size becomes large • Malignant-rapid growth, metastasize, destroy tissue around them Treatment • Chemotherapy-targets quickly dividing cells, both cancer and healthy • Radiation Therapy-high energy radiation targets only tumor

19. Prokaryotic Cell Division • Binary fission • Asexual reproduction • No nucleus, only nucleoid region • Single circular chromosome • Cell wall