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THE CELL CYCLE

THE CELL CYCLE. Questions We Have. Why do cells divide? How do cells divide? What controls cell division? What’s binary fission anyhow? What happens when things go wrong?. Lets Review The Cell Theory?. All living things are made up of cells and the products formed by cells.

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THE CELL CYCLE

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  1. THE CELL CYCLE

  2. Questions We Have • Why do cells divide? • How do cells divide? • What controls cell division? • What’s binary fission anyhow? • What happens when things go wrong?

  3. Lets Review The Cell Theory? • All living things are made up of cells and the products formed by cells. • Cells are the units of structure and function. • In 1855, Rudolf Vichow adds the idea that all cells come from preexisting ones (No more spontaneous generation).

  4. So, why do cells divide? • Growth – adding more cells • Renewal – replace old, worn out cells • Repair – fixing things that are broken • Reproduction – creating sperm and egg

  5. A few terms we need to know… • Genome – A cells endowment of DNA. All of its genes • Chromosomes – Discrete molecules of DNA and any associated proteins called histones. • Somatic Cells – Body cells containing pairs of chromosomes (diploid, 2n number = 46 in humans). • Gametes – Reproductive cells: sperm & egg containing ½ the chromosome number (haploid, n = 23) • Sister chromatids – Duplicate chromosomes held together by a centromere which contains a kinetochore for spindle fiber attachment.

  6. Chromatin Packing

  7. Terms continued… • Mitosis – The division of the nucleus in eukaryotic cells. • Cytokinesis – The division of the cytoplasm creating two daughter cells. • Binary fission – Prokaryotic cell division

  8. Binary FissionWhat Bacteria Do

  9. The Mitotic Cycle in Eukaryotic Cells Can you pick out the stages of plant cell mitosis?

  10. The Mitotic Cell CycleThings we didn’t tell you about Freshman year…

  11. Regulation of the Cell Cycle • The frequency of cell division varies with the kind of cell. • Regulation occurs at the molecular level. • Regulation by both external and internal controls occurs at checkpoints. • Cell division stops at checkpoints until overridden by go-ahead signals. • G1 checkpoint called “restriction point” in mammalian cells.

  12. Cell Cycle Check Points G0

  13. Cyclins & Cyclin-dependent Kinases • Kinases that drive the cycle are present in constant concentration in growing cells. • Binding cyclins activates kinases. • Cdks = Cyclin dependent kinases • Cyclin levels rise and fall (they cycle) • MPF = Maturation-promoting factor is a complex of cyclins and kinases that promotes passage from G2 into mitosis.

  14. External Signals • Chemical and physical factors. • Growth factors like PDGF (platelet-derived growth factor. • Density-dependent inhibition. • Anchorage dependence. Internal Signals • Cell surface to volume ratio • Cell age • Chromosome number and position

  15. Cancer • Protooncogenes – Genes that, if damaged, could result in cancer • Tumor Supressor Genes – Genes that hold suppress cell division • P53 – Protein factor that suppresses cell division in damaged cells, or caused apoptosis in heavily damaged cells Check out these websites to learn more The Eukaryotic Cell Cycle and Cancer CANCERQUEST

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