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Cell Division and Mitosis

Cell Division and Mitosis. Chapter 8. Roles of Mitosis. Multicelled organisms Growth Cell replacement Some protistans, fungi, plants, animals Asexual reproduction. Chromosome. A DNA molecule & attached proteins Duplicated in preparation for mitosis. one chromosome (unduplicated).

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Cell Division and Mitosis

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  1. Cell Division and Mitosis Chapter 8

  2. Roles of Mitosis • Multicelled organisms • Growth • Cell replacement • Some protistans, fungi, plants, animals • Asexual reproduction

  3. Chromosome • A DNA molecule & attached proteins • Duplicated in preparation for mitosis one chromosome (unduplicated) one chromosome (duplicated)

  4. Chromosome Number • Sum total of chromosomes in a cell • Somatic cells • Chromosome number is diploid (2n) • Two of each type of chromosome • Gametes • Chromosome number is haploid (n) • One of each chromosome type

  5. Human Chromosome Number • Diploid chromosome number (2n) = 46 • Two sets of 23 chromosomes each • One set from father • One set from mother • Mitosis produces cells with 46 chromosomes--two of each type

  6. Organization of Chromosomes DNA one nucleosome DNA and proteins arranged as cylindrical fiber histone

  7. Fig. 8.4, p. 130

  8. Interphase • Usually longest part of the cycle • Cell increases in mass • Number of cytoplasmic components doubles • DNA is duplicated

  9. Stages of Interphase • G1 • Interval or gap after cell division • S • Time of DNA synthesis (replication) • G2 • Interval or gap after DNA replication

  10. Mitosis • Period of nuclear division • Usually followed by cytoplasmic division • Four stages:(PMAT) Prophase Metaphase Anaphase Telophase

  11. The Spindle Apparatus • Consists of two distinct sets of microtubules • Each set extends from one of the cell poles • Two sets overlap at spindle equator • Moves chromosomes during mitosis

  12. Spindle Apparatus one spindle pole one of the condensed chromosomes spindle equator microtubules organized as a spindle apparatus one spindle pole

  13. Early Prophase - Mitosis Begins Duplicated chromosomes begin to condense

  14. Late Prophase • New microtubules are assembled • One centriole pair is moved toward opposite pole of spindle • Nuclear envelope starts to break up

  15. Transition to Metaphase • Spindle forms • Spindle microtubules become attached to the two sister chromatids of each chromosome

  16. Metaphase • All chromosomes are lined up at the spindle equator • Chromosomes are maximally condensed

  17. Anaphase • Sister chromatids of each chromosome are pulled apart • Once separated, each chromatid is a chromosome

  18. Telophase • Chromosomes decondense • Two nuclear membranes form, one around each set of unduplicated chromosomes

  19. Results of Mitosis • Two daughter nuclei • Each with same chromosome number as parent cell • Chromosomes in unduplicated form

  20. Cytoplasmic Division • Usually occurs between late anaphase and end of telophase • Two mechanisms • Cell plate formation (plants) • Cleavage (animals)

  21. Cell Plate Formation

  22. Animal Cell Division

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