Cell division Mitosis: for growth and healing, ADDS NEW CELLS Results in exact copies of the parent cell, all chromosomes present Meiosis: for gamete formation (egg and sperm) cuts the chromosome number in half so sperm and egg can form zygote

Mitosis Cell division

Phases of Mitosis This proceeds without any pauses between phases The phases are somewhat arbitrary, to help us identify what is happening All phases do not take an equal amount of time; some are longer than others

Prophase Chromosomes become visible Nuclear membrane disappears (Chromosomes are already copied)

Metaphase Chromosomes attach to spindle fibers Chromosomes are pulled to line up on equator of cell Single file

Anaphase Chromatids separate Move to opposite poles

Telophase Opposite of prophase Chromosomes reach the poles Chromosomes uncoil and return to chromatin Nuclear membrane reappears

Cell Differentiation One zygote will develop into 260 specialized cell types A bone cell is different from a blood cell, a nerve cell, a gland cell that secretes a substance, etc.

Cell Differentiation Stem Cells Have the ability to divide without specializing They can become any kind of cell after several divisions One stem cell divides into another stem cell and a PROGENITOR CELL, which is partially specialized