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Understanding the Cell Cycle: Asexual and Sexual Reproduction Overview

This guide explores the intricacies of the cell cycle, highlighting key reproductive processes including asexual reproduction, where a single organism produces genetically identical clones, and sexual reproduction, involving two parents and resulting in genetic diversity. The phases of the cell cycle—interphase and mitosis—are explained in detail, covering G1, S, and G2 stages, followed by mitotic phases: prophase, metaphase, anaphase, and telophase. Insights into cytokinesis and the control mechanisms that ensure proper cell division are also discussed, important for understanding growth, tissue repair, and cancer implications.

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Understanding the Cell Cycle: Asexual and Sexual Reproduction Overview

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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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