Mitosis Chapter 10 What Are Chromosomes? • Strands of DNA • Every organism has a specific number of chromosomes • Before cell division occurs, DNA must be copied so each new cell will have DNA. • Once copied, the two identical strands (or CHROMATIDS) are held together by a CENTROMERE.. Cell Cycle – “Life of a Cell” • Interphase – growth period of cell, longest stage of cell life. 1. G1 phase – growth, more organelles 2. S phase – DNA duplication 3. G2 phase – preparation for mitosis • Cell Division – division of the cell into 2 1. Mitosis – division of the nucleus 2. Cytokinesis – division of the cytoplasm Section 10-2 The Cell Cycle G1 phase M phase S phase G2 phase Mitosis = Cell Division • Prophase – cell prepares to be divided; chromatin condenses, centrioles separate to opposite sides of cell (animal cells only), spindle forms, nuclear membrane breaks down • Metaphase – Chromosomes line up in middle • Anaphase – sister chromatids separate apart • Telophase – new nuclear membranes form and begin to tear the cells in two Cytokinesis Division of the cytoplasm Differences in Cell Division: 1.In animal cells: cleavage of cell membrane 2.In plant cells: a cell plate forms midway between the divided nuclei Mitosis Animation What happens if something goes wrong with the cell cycle? Cancer • Uncontrolled cell division • DNA is damaged by carcinogens or genetically inherited • Cell will not respond to cell cycle regulators • Carcinogens can be radiation or chemicals Tumor Stem Cells • Cell that have not become specialized. • Stem cells can become any type of human cell. Abundant in embryos. • Possible uses in science: treating nerve damage, growing organs, treating diseases.