Mitosis and the Cell Cycle The Cell Cycle

Mitosis and the Cell Cycle!

The Cell Cycle • A living organism has a life cycle. • A life cycle begins with the organism’s formation, is followed by growth and development, and finally ends in death. • Individual cells also have life cycles.

The Cell Cycle n. The sequence of growth and division of a cell. n 95% of cell cycle in interphase n 5% of cell cycle in mitosis

Interphase n Before a cell divides, a copy of the hereditary material must be made so that each of the two new cells will get a complete copy. n Each cell needs a complete set of hereditary material to carry out life functions.

Interphase n After interphase, cell division begins. n The nucleus divides, and then cytoplasm separates to form two new cells.

Mitosis • Mitosis (mi TOH sus) is the process in which the nucleus divides, forming two identical nuclei. • • Each new nucleus also is identical to the original nucleus. Mitosis is described as a series of phases, or steps. • The steps of mitosis in order are named prophase, metaphase, and telophase.

Prophase n Nuclear envelope disappears n Chromosomes condense – can see sister chromatids n Spindle forms

Metaphase n Chromosomes move to the equator of spindle n Each chromatid is attached to spindle with centromere

Anaphase n Centromeres split n Sister chromatids are pulled apart to opposite poles of the cell n Each chromatid is now a separate chromosome

Telophase n Spindle fibers start to disappear n Chromosomes begin to uncoil n New nucleus forms

Cytokinesis n Cytoplasm divides n Two new daughter cells are now separate

Results of Mitosis n Mitosis is the division of the nucleus, and it produces two new nuclei that are identical to each other and the original nucleus. n 46 chromosomes in all body cells EXCEPT in sperm and egg cells.

Results of Mitosis • Cell division allows growth and replaces worn out or damaged cells. • If you cut yourself, the wound heals because cell division replaces damaged cells. • Another way some organisms use cell division is to produce new organisms.

Class Activity Mitosis “Comic” Strip Create an illustrated guide to the steps of Mitosis