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Mitosis

Mitosis. What is Mitosis?. Division of the nucleus plus division of the cell itself ( cytokinesis ) Produces two identical daughter cells during prophase, metaphase, anaphase, and telophase. Stages of the cell cycle.

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Mitosis

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  1. Mitosis

  2. What is Mitosis? • Division of the nucleus plus division of the cell itself (cytokinesis) • Produces two identical daughter cells during prophase, metaphase, anaphase, and telophase.

  3. Stages of the cell cycle • An ordered set of events, culminating in cell growth and division into two daughter cells. • Non-dividing cells not considered to be in the cell cycle.

  4. Stages of the cell cycle • INTERPHASE • G1 stage = "GAP 1” cell growth • Sstage = "Synthesis” • DNA replication • G2 stage = "GAP 2” organelle production • MITOSIS • M phase = nucleus divides • CYTOKINESIS • cytoplasm divides  daughter cells

  5. Regulation of the Cell Cycle • Very complex • Errors can lead to cancer. • In cancer, regulation of the cell cycle goes awry • Normal cell growth & behavior is lost.

  6. Ploidy • Number of sets of chromosomes in a cell • Haploid (n)-- one set chromosomes • Diploid (2n)-- two sets chromosomes • Most plant and animal adults are diploid (2n) • Eggs and sperm are haploid (n)

  7. Chromosome Characteristics • Diploid set for humans; 2n = 46 • Autosomes = body chromosomes • Female-sex chromosomes = homologous (XX) • Male-sex chromosomes = non-homologous (XY)

  8. Interphase • The cell is metabolizing, growing and preparing for mitosis

  9. Interphase • Chromosomes are not clearly seen • Nucleolus may be visible • In animal cells ONLY, a pair of centrioles may start moving into position.

  10. Prophase • Chromatin begins to condense and becomes visible. • Nucleolus disappears. • Centrioles begin moving to opposite ends of the cell

  11. Prophase (con’t) • Nuclear membrane dissolves • Microtubules attach and chromosomes begin moving.

  12. Metaphase • Spindle fibers align the chromosomes along metaphase plate. • Helps to ensure each new nucleus will receive one copy of each chromosome.

  13. Anaphase • Paired chromosomes separate and move to opposite sides

  14. Telophase • Chromatids arrive at opposite poles • Membranes re-form around daughter nuclei. • Chromosomes & spindles disperse and are no longer visible. • Cytokinesis may begin

  15. Cytokinesis: Animals • Fiber ring of protein called actin around center of cell contracts • Pinches cell into two daughter cells

  16. Plants • In plant cells, the rigid wall requires that a cell plate be synthesized between the two daughter cells.

  17. Asexual Reproduction • Uses only mitosis • Cells duplicate to form 2 exact copies (clones) of each other • Most primitive form of reproduction • NO GENETIC VARIATION • Used by higher organisms when conditions are not favorable for sexual reproduction

  18. Types of Asexual Reprod. • Binary fission • Budding • Fragmentation • Regeneration • Spore formation • Parthenogenesis

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