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Cell Growth and Division • The human body forms two types of cells, body cells and sex cells. • You produce more body cells than sex cells Why do cells divide? • For reproduction – asexual reproduction • one-celled organisms with same DNA as parent. • For growth – from fertilized egg to multi-celled organism • For repair & renewal – Regeneration is when a body part regrows and may form a new organism. amoeba Cell cycle M Mitosis G2 Gap 2 • Cell has a “life cycle” • Broken down into steps cell is formed from a mitotic division cell grows & matures to divide again G1, S, G2, M epithelial cells, blood cells, stem cells S Synthesis cell grows & matures to never divide again liver cells G1G0 brain / nerve cells muscle cells G1 Gap 1 G0 Resting Interphase First step of the Cell Cycle • Divided into 3 phases: – G1 = 1st Gap (Growth) • cell doing its “everyday job” • cell grows – S = DNA Synthesis • copies chromosomes – G2 = 2nd Gap (Growth) • prepares for division • cell grows (more) • produces organelles, proteins, membranes Interphase • During this phase, cells go through periods: rapid growth, DNA synthesis. • Cells spend the majority of their time in interphase. • Nucleus well-defined – DNA loosely packed in long chromatin fibers • Chromosomes are structures that contain DNA, that determine what traits a living thing will have. • • • • During cell division each chromosome has to make an exact copy of itself. During Interphase, you can’t see chromosomes. As the cell prepares to divide the chromosomes become compact and visible. Centromere: is found in the center of the Chromosomes. Cell Cycle Interphase On the back: write and answer the questions: What type of cells go through all four steps of the cell cycle (G1, S, G2, M)? What type of cells don’t divide? Chromosomes Mitosis Second step of the Cell Cycle • Dividing cell’s DNA between 2 daughter nuclei • 4 phases – prophase – metaphase – anaphase – telophase green = key features Prophase • Chromatin condenses to form visible chromosomes • Centrioles (are organelles that help the cell divide) move to opposite poles of cell • Microtubules come from the centrioles to form mitotic spindle – Helps coordinates movement of chromosomes • Nucleolus disappears • Nuclear membrane breaks down Prophase “pasta” green = key features Metaphase • Chromosomes align along middle of cell • meta = middle – spindle fibers coordinate movement Metaphase green = key features Anaphase • Sister chromatids separate – move to opposite poles – pulled at centromeres • increased production of ATP by mitochondria • Poles move farther apart Anaphase green = key features Telophase • Chromosomes arrive at opposite poles – daughter nuclei form – nucleoli form – chromosomes disperse • no longer visible under light microscope • Spindle fibers disperse • Cytokinesis begins – cell division Telophase Cytokinesis in Animals • Animals – constriction belt of actin microfilaments around equator of cell • cleavage furrow forms • splits cell in two – Cytoplasm pinches off Cytokinesis in Plants • Plants – Since they have a cell wall, the cleavage furrow would not work instead a cell plate forms, which helps to make a new cell wall and new cell membrane Results of Mitosis • The division of the nucleus • Two new cells that have the same number of chromosomes as the original cell. Overview of Cell Cycle interphase prophase I.P.M.A.T. (pro-metaphase) cytokinesis metaphase anaphase telophase Mitosis in whitefish blastula Mitosis in animal cells Mitosis in plant cell onion root tip metaphase anaphase Tumors • Tumor: is a mass of abnormal cells that develops when cancerous cells divide and grow uncontrollable 2 types: 1. Benign Tumors: are non cancerous tumors 2. Malignant Tumors: are cancerous tumors Cancer • There are over 200 types of cancers • Occurs in almost any part of the body. • Are named by the place in the body where they begin. Treating and Preventing Cancer • Treatment – Surgery • Usually the best treatment because they can completely remove the tumor. – Radiation • Consists of beams of high-energy waves. – Chemotherapy • Is the use of drugs to treat a disease, which is carried throughout the body through the bloodstream • Preventing – Avoid smoking – Eating health diet – Protect their skin from bright sunlight
