Transcript Mitosis PPT
Mitosis Division of regular (somatic) cells Mitosis • First you duplicate DNA • Why? – You have 2 pairs of 23 chromosomes – If cell splits, you will only have 1 pair – Duplicate DNA, cell splits, still have 2 pair Sex chromosomes- X and Y: XX is female in humans, XY is male Interphase • Prior & After Mitosis • G1 period – 90% of cell life spent here – Cell goes about it’s business • S period – DNA is duplicated • G2 period – Cell prepares to divide • Cannot see DNA- uncoiled as chromatin 1. Prophase • DNA becomes visible as chromosomes • Nuclear membrane dissolves • Centrioles migrate to opposite poles • Spindle fibers form Easy to remember- Prophase- proceeding into mitosis 2. Metaphase • Spindle fibers attach to centromeres • Chromosomes line up at midline of the cell Pole Spindle Equator Pole Easy to remember- metaphase, DNA at middle 3. Anaphase • Spindle fibers pull apart centromeres • One chromatid goes to each centriole (they look like V’s) Easy to remember- anaphase, apart they go 4. Telophase • Chromatids reach centrioles • Mitosis ends when new nuclear membranes form • Some evidence of cell dividing Easy to remember- telophase, terminal phase Last part- Cytoplasmic division • Technically not in mitosis – Animal cell- pinching of cell membrane- cleavage – Plant cell- formation of new cell wall- cell plate – DNA becomes non-visible, back to chromatin • Daughter cells enter G1 period of interphase