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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,

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Presentation on theme: "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,"— Presentation transcript:

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

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