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The Cell Cycle

The Cell Cycle. Reproduction. Asexual Reproduction: Involves only 1 organism New individual is genetically identical to parent- clone Single celled organisms - binary fission : cell divides in 2. Multicelled organisms: Budding Plant propagation Parthenogenesis. Reproduction.

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The Cell Cycle

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  1. The Cell Cycle

  2. Reproduction • Asexual Reproduction: • Involves only 1 organism • New individual is genetically identical to parent-clone • Single celled organisms • - binary fission: cell divides in 2

  3. Multicelled organisms: • Budding • Plant propagation • Parthenogenesis

  4. Reproduction • Sexual Reproduction: • Involves 2 parental organisms • New individual is different from either parent • Leads to greater genetic diversity

  5. Sexual Reproduction:

  6. Chromosome Structure • Chromatin: DNA and protein in long, thin thread-like, invisible form

  7. Chromosome Structure • Chromosomes: Condensed chromatin that appear right before cell division • Sister chromatids- contain exact copies of DNA- • Centromere- protein “button” holds chromatids together

  8. Chromosome Structure

  9. The Cell Cycle • The time it takes from 1 cell division to the next • Varies in length of time depending on cell type

  10. The Cell Cycle • Function -asexual reproduction • Single celled organisms -produce new individuals- • Multicelled organisms – • Growth -increase in size by increasing in cell number • Tissue replacement and repair

  11. The Cell Cycle Two alternating periods • Interphase- growth • Mitosis- division Interphase Growth Division Mitosis

  12. Phases of the Cell Cycle

  13. The Cell Cycle Interphase: • The growth period. • Longest phase of the cell cycle • Cell spends 98% of time in interphase • 3 stages

  14. 3 Stages of Interphase G1 -1st Gap phase: • The cell growsin size and carries on normal functions S - Synthesis phase: • DNA Replication • Chromosomes copied in preparation for cell division. G2 - 2nd Gap phase: • Structures needed for cell division are assembled. • No turning back- cell division will occur

  15. Phases of the Cell Cycle How the Cell Cycle Works

  16. The Cell Cycle • Mitosis: • The division period • Division of the nucleus • Four distinct phases. • Prophase • Metaphase • Anaphase • Telophase The Cell Cycle

  17. Prophase • First phase of mitosis • Chromatin condenses and chromosomes become visible • Nuclear membrane and nucleoli disappear • Structures necessary for cell division appear • Centrioles- barrel shaped, 2 pair, each moves to opposite poles • Spindle fibers- span the two poles

  18. Prophase

  19. Metaphase • Chromosomes line up along the midline of the cell

  20. Anaphase • Centromeres and sister chromatids separate • Spindle fibers shorten and pull chromatids, now called chromosomes, toward opposite poles

  21. Telophase • Reverse of Prophase • Begins when chromosomes stop after reaching poles • Chromosomes decondense to less visible chromatin form • Nucleoli reappear • Nuclear membrane appears around each set of chromosomes

  22. Telophase

  23. Cytokinesis Division of the cytoplasm and organelles Results in 2 daughter cells New cells begin a new cell cycle Different for plants and animals

  24. Animal Cell Cytokinesis • Cleavage furrow-cell membrane pinches in Animation: Mitosis Mitosis

  25. Plant Cell Cytokinesis • Cell plate formation- new cell wall is added to separate 2 daughter cells onion root tip

  26. Control of the Cell Cycle • A series of enzymes monitor a cell’s progress from phase to phase. • A disrupted cell cycle can result in excessive cell division, or cancer

  27. Skin Cancers http://www.skincancer.org/skin-cancer/melanoma/melanoma_2.html

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