Cell Division Mitosis and Meiosis

The Cell Cycle Mitosis Interphase

Cell Growth Prior to mitosis, the cell is in Interphase Interphase is a time where The cell grows Organelles replicate DNA is copied Most of a cells life is spent in interphase

Mitosis Occurs in body cells (somatic cells) Results in 2 daughter cells identical to the parent cell 4 phases: prophase, metaphase, anaphase, and telophase

Prophase Stage 1 of Mitosis DNA winds up to form chromosomes Nuclear membrane (membrane around the nucleus) disappears

Metaphase Stage 2 of Mitosis Chromosomes line up at equator (center) of the cell

Anaphase Stage 3 of Mitosis Chromosomes split - each half is pulled to opposite sides of the cell

Telophase Stage 4 of Mitosis Nuclear membranes form around each set of chromosomes and the chromosomes unwind to form strands of DNA

Cytokinesis After mitosis occurs, the cells must split - this process is called cytokinesis There are two methods - one for cells without a cell wall, like animal cells, and one for cells with a cell wall, like plant cells

Cytokinesis - No Cell Wall The membrane starts to pinch inward, between the two nuclei It will continue to pinch, until the cell splits into two new cells

Cytokinesis - Cell Wall Cell forms a cell plate between the two nuclei This cell plate provides foundation for new cell wall Membranes form inside cell walls, and end up with two daughter cells

Meiosis - Formation of Sex Cells Occurs in sex cells (eggs and sperm) Results in 4 daughter cells Each with HALF the DNA of the parent cell All are different from one another AND parent Split into two Stages, each with 4 phases

Prophase I DNA winds up into chromosomes Nuclear membrane disappears

Metaphase I Chromosomes line up at equator Line up next to homogolous chromosome (e.g. chromosome 1 from dad lines up next to chromosome 1 from mom)

Anaphase I One chromosome from each pair is pulled to opposite sides of the cell

Telophase I & Cytokinesis Nuclear membrane forms around each set of chromosomes Chromosomes may unwind Cells split

Prophase II Nuclear membrane disappears Chromosomes wind up

Metaphase II Chromosomes line up at equator

Anaphase II Chromosomes split, each half pulled to opposite sides of the cell

Telophase II & Cytokinesis Nuclear membrane reforms around each set of chromosomes Chromosomes unwind Cells split

Compare Mitosis/Meiosis 4 cells formed Daughter cells have 1/2 DNA of the parent cell All 4 are different Occurs in sex cells 8 phases/2 stages 2 cells formed Daughter cells identical to parent cell Occurs in body cells 4 phases Both Prophase Metaphase Anaphase Telophase Cells divide