Chromosomes • Are made of DNA • Each chromosome consists of sister chromatids attached at a centromere
Cell Cycle • During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each with each of which then begins the cycle again. • Interphase – time for growth and regular cell activity. • Most of a cells life is spent in Interphase.
Mitosis • The division of somatic or regular cells. • Its divided into 4 phases. • Remember Interphase is NOT part of Mitosis.
Prophase • First stage of Mitosis • Chromatin condenses into chromosomes • Centrioles separate and a spindle fiber begins to form. • Nuclear membrane breaks down
Metaphase • Second Phase of Mitosis • Chromosomes line up in the middle of the cell. • Each chromosome is connected to a spindle fiber.
Anaphase • Third Phase of Mitosis • The sister chromatids separate into individual chromosomes and move apart to opposite ends of the cell.
Telophase • Fourth and Final Stage of Mitosis • Chromosomes gather at opposite ends of the cell and lose their distinct shapes • Two new nuclear membranes have formed.
Cytokinesis • The cytoplasm pinches in half. • Each daughter cell has an identical set of duplicate chromosomes
Regulating the Cycle • A protein call cyclin helps regulate the cell cycle in eukaryotic cells. • They respond to internal and external events. These proteins are regulators.
When Things Go Wrong • Cancer cells do not respond to the signals that regulate the growth of most cells. • As a result, they form masses of cells called tumors that can damage surrounding tissues.