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Why does a cell divide? • Efficiency – Smaller the cell = quicker it can work • Transport of Substances • Cellular communication – Ratio of surface area to volume Other reasons for cellular division • Growth • Replace damaged cells The Cell Cycle • Cell reaches max size it stops growing or divides – Cells reproduce by growing and dividing = cell cycle • 3 main stages of cell cycle 1. Interphase – cell grows, replicates DNA 2. Mitosis – nucleus and nuclear material divide 3. Cytokinesis – cytoplasm divides 3 Stages of Interphase Gap 1 (G1) • normal functions Synthesis (S) • Cell copies DNA Gap 2 (G2) • Cell prepares for mitosis Mitosis • Cell’s DNA separates – Creates 2 identical daughter cells – Same Number of Chromosomes • 4 Stages – Prophase, Metaphase, Anaphase, Telophase 1. Prophase • Chromatin condenses into chromosomes – X – shaped – Consist of two chromatids – identical copies of DNA – Chromatids are connected at a centromere 1. Prophase • Nuclear membrane disappears • Spindle apparatus appears – Spindle fibers, centrioles, and aster fibers 2. Metaphase • Chromatids Line up at center of cell 3. Anaphase • Chromatids pull apart 4. Telophase • • • • Chromosomes arrive at the poles Chromosomes unwind Two nuclear membranes begin to form Spindle apparatus disappears Cytokinesis • Divides cytoplasm • Animal Cells – Microfilaments constrict/pinch the cytoplasm • Plant Cells – Cell plate forms between two daughter nuclei – Cell walls then form on either side of cell plate • http://highered.mcgrawhill.com/sites/0072495855/student_view0/ch apter2/animation__mitosis_and_cytokinesis.h tml • http://www.sumanasinc.com/webcontent/ani mations/content/mitosis.html • https://www.youtube.com/watch?v=L0kenzoeOM Cancer • Uncontrolled cell division • Tumors begin with a single cell that reproduces by mitosis – Cells in tumors divide continuously • Metastasis: Process in which cells are invasive and move to other sites in the body The Cell Cycle and Cancer • Benign = not cancerous – Do not invade neighboring tissue or spread • Malignant = cancerous – Readily invade neighboring tissues – May also detach and lodge in distant places – metastasis G2/M checkpoint 4 Cell division 3 DNA repair 1 Mitosis G2 G1 • Checkpoints in the cell cycle regulate cell division 2 Cell grows, doubles in size S Chromosome duplication G1/S checkpoint Stepped Art p. 181 How does it happen? • Oncogenes are activated – Normal function: cell growth, gene transcription • Tumor suppressor genes are inactivated – Normal function: DNA repair, cell cycle control, cell death Tumor suppressors • “Guardian(s) of the genome” • Often involved in maintaining genomic integrity (DNA repair, chromosome segregation) • Mutations in tumor suppressor genes lead to the “mutator phenotype”—mutation rates increase • Often the 1st mutation in a developing cancer • P53 and Rb Causes of Cancer • Mutation: change in genetic makeup • Any agent that causes cancer is called a carcinogen and is described as carcinogenic • Infection – Viruses (EBV, hepatitis B, papilloma) – Bacteria (Helicobacter) • • • • • • • • Lifestyle Risks Smoking Diet high fat and low in fruits and vegetables Lack of exercise Unprotected exposure to the sun, (UV) rays Obesity Stress Jobs – exposed to chemicals, etc Radiation Environmental Risks • Second hand smoke • PCB’s • Air pollution • Industrial pollution • Chemical exposures – tar from cigarettes – some foods Inherited Risks • Less than 15% of cancers are inherited • Some families are more susceptible to getting certain cancers – You can’t inherit cancer its just that you maybe more susceptible to getting it Treatment Chemotherapy treatment • uses medicine to weaken and destroy cancer cells in the body • affects the whole body Radiation therapy (also called radiotherapy) • high-energy rays are used to damage cancer cells and stop them from growing and dividing • local treatment; it affects cancer cells only in the treated area Cancer Prevention Healthy lifestyle • Exercise and proper breathing • Balanced diet • Complete rest and sleep • Water • Eating Fruit Explain what happens in each step of mitosis. Agenda for 1. Review mitosis (video?) 2. Mitosis Cell Lab If a cell has 150 chromosomes how many daughter cells are created at the end of mitosis? How many chromosomes are in each cell? Agenda for 1. Finish lab 2. Finish worksheets 3. Start cancer notes What is cancer? Agenda for 1. Cancer Notes 2. Go over worksheets and lab 3. Cancer worksheet
