Mitosis and meiosis
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Mitosis and Meiosis. Chromosomes made of DNA wrapped around histone protein (beads) to make nucleosomes. Chromatin - mixture of DNA and protein that makes up chromosome Chromosomes make possible the precise separation of DNA during cell division. Chromosome parts Telomere - end

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Mitosis and meiosis

  • Chromosomes made of DNA wrapped around histone protein (beads) to make nucleosomes

Mitosis and meiosis

  • Chromatin - mixture of DNA and protein that makes up chromosome

  • Chromosomes make possible the precise separation of DNA during cell division

Mitosis and meiosis

Chromosome parts

Telomere - end

Centromere - middle

Arms - chromatids

Mitosis and meiosis

  • Cell Cycle - series of events in the growth and division of a cell

Mitosis and meiosis

  • Interphase (‘in between’)

  • 1) cell grows (G1)

  • 2) DNA duplicates (S)

  • 3) Cell produces organelles for division (G2)

    Basically, the cell is growing and getting ready for division

Mitosis and meiosis

  • Chromosomes duplicate themselves during normal cell lifetime (interphase)

Mitosis and meiosis

Mitosis and meiosis

  • After interphase - cells have 2 sets of each chromosome from mom and dad (4N)

Mitosis and meiosis

  • Mitosis - cell division starts in the nucleus

  • Stages:

  • Prophase

  • Metaphase

  • Anaphase

  • Telophase

Mitosis and meiosis

  • 1) Prophase - DNA condenses, spindle starts to form

Mitosis and meiosis

  • 2) Metaphase - duplicated chromosomes line up, spindles connect to centromeres

Mitosis and meiosis

3) Anaphase - sister chromatids separate and move toward centrioles (where spindles originate)

Mitosis and meiosis

4) Telophase - chromosomes unwind and nuclear envelope forms

Mitosis and meiosis

  • Cytokinesis - final splitting of one cell into two

    Animal cells - cell membrane is pinched inward

Mitosis and meiosis

  • Plant cell cytokinesis- membrane too rigid to move due to cell wall - so a plate forms halfway between 2 new nuclei


  • Cell division to produce gametes (sex cells)

Mitosis and meiosis

  • Ploidy - number of sets a chromosome in a cell nucleus

  • Notice these chromosomes

    are not duplicated

Mitosis and meiosis

  • Homologous (ho - mahl-a-gus) - chromosomes carry same genes (but one from mom, one from dad)

Mitosis and meiosis

  • Meiosis (4N) - can be broken into Meiosis I and Meiosis II

  • Before Meiosis I, chromosomes replicate

  • Before Meiosis II, chromosomes do not replicate

Mitosis and meiosis

Mitosis and meiosis

  • Step 2) (4N)Prophase I- paired homologous chromosomes form tetrads

  • Crossing over -

    homologous chromosomes

    exchange alleles!

    Crossing over creates new

    Combinations of alleles

    In daughter cell

    (shuffles genetics)

Mitosis and meiosis

  • Tetrad (4N) - two copied homologous chromosomes

Mitosis and meiosis

  • Step 3) (4N)Metaphase I - paired homologous chromosomes line up in center of the cell and are pulled apart

Mitosis and meiosis

  • Step 4) (4N)Anaphase I - spindle fibers pull each homologous pair towards opposite ends

Mitosis and meiosis

  • Step 5) (4N)Telophase I - nuclear membranes form, then cytokinesis occurs

Meiosis i vs mitosis
Meiosis I vs. Mitosis (4N)

  • Daughter cells in meiosis I do not have identical chromosomes as parent cell

  • 2 daughters are haploid because during division, each daughter gets one half of the homologous pair

  • Crossing over makes it so each daughter cell doesn’t just have chromosome from one parent

Meiosis ii
Meiosis II (4N)

  • Difference: chromosomes do not replicate before this division

Meiosis ii1
Meiosis II (4N)

  • In meiosis II, the two

    daughter cells from

    meiosis I split back

    into separate


    (go haploid)

Mitosis and meiosis