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Mitosis: Cell Division Terminology • DNA – made of nucleic acids, housed in the nucleus, contains genes • Chromatin – long strands of DNA that are wrapped around proteins (histones) • Nucleosome – the DNA/ histone complex Why does mitosis happen? • Surface area to volume ratio – As a cell grows, the volume grows faster than the surface area – Not enough space in the cell membrane to send wastes out or to bring food in • Signal is sent to the cell – An organism needs to grow – To repair damage Structure of a Chromosome •Chromosome – a structure that is made of DNA and the proteins associated with it •Chromatid – one of the 2 exact copies of the DNA – often referred to as “sister chromatids” – the 2 of them together make a chromosome •Centromere – the point where the 2 chromatids are connected together to make a chromosome Homologous Chromosomes •two chromosomes that code for the same traits. One is from mom the other is from dad Cell Cycle • Interphase – Majority of a cell’s life – Cell grows – Chromosomes duplicate • Mitosis – Creates 2 daughter cells that are identical to the parent cell – Cell division Interphase • G1 – Growth One – The cell spends most of its life • S – Chromosomes are duplicated • G2 – Organelles and other parts needed for cell division are duplicated Mitosis • Prophase – the chromosomes become visible – the nuclear envelope disappears – pro = first • Metaphase – the chromosomes line up in the middle of the cell • Anaphase – the sister chromatids move away from each other • Telophase – begins as chromatids reach opposite ends of the cell Cytokinesis • The cytoplasm and organelles are divided between the two sides • Plants: – A cell plate begins forming • Animals: – A cleavage furrow forms as the cell pinches inward Levels of Organization Cells Tissues Organs Organ Systems Organism When Good Cells Go Bad! Facts about cancer • Who will develop it? – ½ of men and 1/3 of women in the U.S. will develop cancer in their lifetime • What is it? – Uncontrolled cell division • What causes the cell to keep dividing? – Failure to produce internal regulators or respond to external regulators Causes of Cancer • a. Tobacco use – lung, mouth, esophageal, cervical cancer • b. Asbestos – lung cancer • c. Radiation exposure • d. Viral infection - HPV • e. Charred meat – colon cancer • f. Genetic • g. Chemical exposure • h. UV exposure (sun or tanning bed) – skin cancer • i. Drinking more than one drink a day for women or 2 a day for men Kinds of Cancer • Metastatic – More dangerous – Cancer travels in the body • Nonmetastatic – Usually less dangerous – Cancer does not travel Not all cancers form tumors and not all tumors are cancerous! How does cancer spread? Pancreatic Cancer