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Cell Reproduction

Cell Reproduction. Chapter 8. Henrietta Lacks cervical cancer HeLa Cells. Cell Division. Mitosis How body cells divide Makes exact copy – clone - of parent cell Identical daughter cells Meiosis Makes sex cells – eggs and sperm Contain only one chromosome of a pair

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Cell Reproduction

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  1. Cell Reproduction Chapter 8

  2. Henrietta Lacks • cervical cancer • HeLa Cells

  3. Cell Division • Mitosis • How body cells divide • Makes exact copy – clone - of parent cell • Identical daughter cells • Meiosis • Makes sex cells – eggs and sperm • Contain only one chromosome of a pair • Half the normal number of chromosomes

  4. Prokaryotic cell division • No nucleus or organelles, and only one circular chromosome • Process is called binary fission • Not mitosis since there is no nucleus to divide

  5. http://www.anselm.edu/homepage/jpitocch/genbio/binfission.JPGhttp://www.anselm.edu/homepage/jpitocch/genbio/binfission.JPG

  6. Eukaryotic cell division • More complicated • More DNA • Chromosomes come in pairs: • homologous chromosomes

  7. Cell cycle • All the processes from one division to the next: • Interphase – “resting stage” • Mitosis – nuclear division • Cytokinesis – division of the cytoplasm

  8. Interphase • Cell is busy doing its job – just not dividing • Nerve cells spend most of life in interphase • Cancer cells spend little time in interphase • Three parts: • G1 or Gap 1 or growth phase • S phase : Synthesis of DNA ; cell is committed to division • G2 or Gap 2

  9. Mitosis • Refers specifically to division of the nucleus • Four phases: • Prophase • Metaphase • Anaphase • Telophase PMAT

  10. Prophase • Chromosomes wind up or condenses • 2 meters / cell • Linked by centromere • Sister chromatids • Nucleoli disappear; mitotic spindle forms from the centrioles

  11. Prometaphase or late prophase • Transition phase – to cell it is all part of one process • Nuclear membrane disappears • Chromatids attach to fibers of mitotic spindle by means of specialized structure called a kinetochore

  12. Metaphase • Chromosomes line up in the center of the cell at the metaphase plate – a disc • Remain this way for about an hour

  13. Anaphase • Centromere splits • Microtubles of mitotic spindle pull members of each pair of duplicate chromosomes to opposite sides of the cell.

  14. Telophase • Mitotic spindle disappears • Nuclear membranes form • Chromosomes unwind

  15. Cytokinesis • Division of the cytoplasm • Accompanies mitosis • Begins in anaphase and finishes after telophase • Animal cells form a contractile ring using actin – one of the proteins found in muscles. • Indentation is called the cleavage furrow • Pinches the cells apart

  16. Plant cells • Mitosis occurs in plants as in animal cells, but cytokinesis is different because of the plant cell wall. • A disc of new membrane called the cell plate forms between the two cells during telophase and expands until it reaches the edges of the cell membrane. • The new cells then make cellulose fibers to form new cell walls.

  17. Control of cell division • Cell senescence – cells reproduce only a certain number of times and then stop. • May be due to telomeres –repeating series of bases at the end of chromosomes that decrease with each division • Telomerase • Apoptosis – programmed cell death –”suicide genes”

  18. http://www-ermm.cbcu.cam.ac.uk/fig001nkg.gif

  19. Contact inhibition • Cells divide until they establish contact with other cells on all sides.

  20. Other factors • Cell size • hormones • Growth factors • Cyclins • Genes: • Oncogenes – want these turned off • Oncology – the study of cancer • Tumor suppressor genes – want these turned on

  21. Tumors - neoplasms • Cells have lost control over cell division • Benign tumors grow only in one area • Cancers invade local tissues (look like a crab) and can metastasize or spread to other areas of the body through the vascular or lymphatic systems

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