The Cell Cycle The steps eukaryotic cells progress through during their lifetime. Cell size surface area and volume Cells are very small. Why? As a cell grows the volume increases and the amount of surface increases. However, the amount of surface area does not increase enough to match the greater volume allowing all needed materials to enter and exit the cell. New cells, why do we need them? Every day 50 to 70 billion cells die in your body from aging, this is called programmed cell death and injury. The Cell Cycle and cell division. Ch. 8 We need cells to grow* To make Repairs To replace old cells, like skin and Red blood cells. Some single celled organisms, like bacteria and protists reproduce by cell division The Cell Cycle* Mitosis is nuclear division Cytokinesis is Cell division Cell Division Restriction Points* Cancer* Causes.why cells cant stop dividing U.V light Chemicals, mutagens X-rays Replication errors Viruses Cancer Wutation in Proto-oncogenes create oncogenes. Mutation ot tumor supressing genes. Mutations that may lead to cancer. https://science.education.nih.gov/sup plements/nih1/cancer/activities/activit y2_animations.html Watch cell cycle animations 1, 2, 3, 4 and 5 Be sure to note how cancer is related to Protooncogenes and tumor suppressor genes!!! Be ready to discuss them. Mitosis A cell must create two identical nuclei before it divides. Chromosome number must stay the same. The creation of the two nuclei is called mitosis. Mitosis, is nuclear division* The period between cell divisions. Cells are actively doing their specific functions. Mitosis may occur at the end of Interphase if the cell is destined to divide Interphase Steps of mitosis Prophase Metaphase Anaphase Telophase There are 4 steps in nuclear division Each phase of mitosis is described in the next several slides. Read each slide for a description. Prophase, nuclear membrane and nucleolus disappear. The replicated chromosomes condense and become visible. The centromere holds the two copies together, The spindle begins to form. Metaphase, Sister chromatids attach to the spindle, at the equator of the cell. The spindle is a network of fibers the chromosomes will travel down when they separate. Anaphase, the centromere breaks and the chromosomes separate and move towards two poles Telophase, 2 nuclei begin to reform, the spindle dissolves, nucleolus reforms, chromosome uncoil, then cell divides by cytokinesis [cell plate in plants, cleavage furrow in animal cells] DNA replication Replication enzymes Proofreader enzymes locate damaged DNA. Damaged DNA removed DNA Polymerase adds new nucleotides A-T C-G Ligase seals the sugar phosphate gaps DNA repair http://www.sciencekids.co.nz/videos/biology/m itosis.html View the Video How to view cells undergoing mitosis Onion root cells have areas of rapid cell division Interphase, the phase between cell divisions when cells doing their normal function. Use the 2 root section handouts. Not Label each cell with an I, P, M, A, T Count up the number of cells in each phase. Shsare your counts with the class. Enter your data and class data into the table. Calculate the % for each phase. Answer the 5 questions and make the pie chart. Mitosis lab Lab Activity Get a prepared slide and on a microscope find the four stages of mitosis, draw each stage in your lab book. Conunt the # of prophase ___ metaphase ___ anaphase ___ telophase ___ interphase ___ Conunt the # of prophase ___ metaphase ___ anaphase ___ telophase ___ interphase ___ Conunt the # of prophase ___ metaphase ___ anaphase ___ telophase ___ interphase ___ Conunt the # of prophase ___ metaphase ___ anaphase ___ telophase ___ interphase ___ Conunt the # of prophase ___ metaphase ___ anaphase ___ telophase ___ interphase ___