Cell division

  • Cell Cycle

    • G1- growth

    • S-dna replication

    • G2- prep for division

    • M-mitosis

    • G0- non dividing state (most cells in us)

  • Chromosomes

    • Tightly coiled pieses of DNa that condenses prioi to division

    • most eukaryotes have 2 copies of every chromosome

    • they form in attached identical pairs

    • Haploid vs. Diploid

      • H:1 copy of every chromosome(n)

      • D:2 copys of every chromosome(2n)

    • human cells have 23 pairs of chromosomes

Phases of Mitosis

  • Interphase: growth, replication of DNA, prep for division. Most of cell life (everything before mitosis)

  • Prophase: Chromosomes condense, and the nuclear envelope begins to break down. Spindle fibers form. in animal cells, centrioles divide

  • Prometaphase: chromosome begins to migrate to cell equator, 2 complete spindels at cell poles

  • Metaphase: Chromosomes align at the cell's metaphase plate, and spindle fibers attach to kinetic horse of chromosomes at the centromeres.

  • Anaphase: Sister chromatids are pulled apart at centromere. migration of chromotids to cell poles mediated by the kinetochore.

  • Telophase: Nuclear envelopes reform around each set of chromosomes, and the chromosomes start to de-condense.

  • Cytokinesis: cell membrane divides. cell splits in two.

    • Animals: a “contractile ring” of microfilament pinches the cell in two. cleavage furrows

    • Plants: vesicles from both cells deposit a new cell wall partition (“cell plate”) in the middle of the of the cell