Cell Division

Cell Types Body Cells (Somatic Cells): All the cells of your body – except the sex cells. Sex Cells – sperm, eggs – (Gametes): The cells used for reproduction.

Body Cells (Somatic Cells) Chromosomes are in matched pairs called homologous (same) chromosomes—same size, shape, and carry the same genes for the same traits). Humans have 46 chromosomes in EACH CELL! (They are found in 23 pairs) Chromosomes are copied right before the process of MITOSIS. Goal: Make more cells—just like the original.

Sex Cells – eggs and sperm (Gametes) Chromosomes occur as singles, not in pairs. Human have 23 chromosomes in each gamete –one of each pair. Sex cells are made during the process of MEIOSIS. Goal: make reproductive cells with half the number of chromosomes.

Structure of a Chromosome Essentially it is wound up DNA Also called Sister Chromatids or Homologous Chromosomes when occurring in pairs One Chromatid is from the “mom” and one is from the “dad”

Cell Cycle

Events of the Cell Cycle G1: first GROWTH phase (growth, synthesis of new proteins and organelles) S: DNA is doubled (chromosomes replicate) G2: second GROWTH phase (organelles and molecules required for division are produced) M phase: Cell Division (Mitosis)

Mitosis – 4 phases Interphase Prophase Metaphase Telophase Anaphase Cytokinesis Metaphase Telophase Anaphase

Interphase is the period of growth that occurs between cell divisions. dfgsg

Prophase Chromosomes become Possible to see.

Metaphase Chromosomes pair and line up in the Middle of the cell.

Anaphase The chromatids are pulled Apart into individual chromosomes and move toward opposite sides of the cell. Individual chromosomes

Telophase Two new nuclei! (not quite 2 cells yet) Chromosomes gather at opposite ends of the cell Two new nuclei! (not quite 2 cells yet)

Cytokinesis Important note: This is not a phase of Mitosis During cytokinesis, the cytoplasm pinches in half. Each new cell is called a daughter cell Each has an identical set of copied chromosomes