DNA Replication1. Interphase – preforming normal functions and preparing for cell divisiona. Gap 1 (G1) – you are born in this phase with 46 chromosomes. Each of these chromosomes has 1 strand of DNA (one double helix)i. Cells are small, metabolically active and growingb. Synthesize (S) – this stage comes right after G1, this is where all DNA is synthesized, meaning the helixes are copied/duplicated.i. Copies of every chromosome in the cell are made1. DNA is pulled apart and a polymerase is used to make complimentary strands2. The double helix splits and creates new halves for each strand.a. There are now 2 identical DNA moleculesii. At the end of this phase there are 46 duplicated chromosomes, which can also be called a sister chromatids1. A centromere is the center of the sister chromatids2. A single sister chromatid is one half of the duplicated moleculeiii. This is all done in the nucleusc. Gap 2 (G2)2. Mitosis – division of cell separates the duplicated chromosomes of a cell into two identical nuclei. Occurs in the division of somatic cellsa. Prophase the first stage of Mitosisi. The chromosomes coil tightly around histones and get rid of the nuclear envelope by disintegrating it. ii. An array of microtubules called spindle fibers form and attach to the kinetochores, the protein bound area of the centromere. iii. Spindle fibers extend between centriole pairs and chromatids connect to the spindle fiversb. Metaphase the second stage of Mitosisi. The spindle fibers line the chromosomes up in the middle of the cellii. Chromatids become alignedc. Anaphase the third stage of Mitosisi. The spindle fibers pull the sister chromatids apart and bring them to opposite poles of the cellii. The spindle fibers then depolymerizeiii. Centromere of each chromatid pair splitsd. Telophase the last stage of Mitosisi. Each new cell prepares to return to interphaseii. The nuclear membranes reform, the nuclei enlarge, and the chromosomes gradually uncoil3. Cytokinesis – the division of the cytoplasm into two daughter cells. This usually begins with the formation of a cleavage furrow and continues throughout telophase. The completion of this marks the end of cell division.4. Parent Cell  G1  S  G2  P  M  A T  daughter cells5. G0 – some cells go on hiatus and enter a G0 phase. This is a form of suspended animation where the cells exit the circle of duplicating and dividing. They aren’t dead or frozen; they just take a leave of absence. This is a quiet phase.6. Check points – there are checkpoints to make sure the cell did what it was supposed to do properly. If it is flagged, the cell goes back and fixes it before moving on to the next step. a. Normal healthy cells listen to these regulators, and if they don’t form properly they drop out of the cell cycle and die.b. Cancer forms when the cells don’t listen to the regulators and keep going, or when they lose control over their division process7. Contact inhibition: when cells form a full sheet and meet their perimeter they stop forming. They make one small thin layer.a. Cutsi. If you get a cut the skin grows back only where the cut was and not beyond that.b. Tumor – can also be referred to as neoplasmi. A mass of cells that have grown out of control and have lost contact inhibition. c. Benign tumor – not cancerous, they can become malignant thoughd. Malignant tumor – this is invasive and starts to spread to the next tissue and take over.i. Metastasize is when parts of the original tumor break off and enter the blood stream of another body system, then a new tumor can form elsewhere in the body. ii. Angiogenesis – you can stimulate nearby blood vessel to sprout new bloodvessels to feed the tumor. These can feed on the tumor at your expense, the energy you are generating causes it to grow. Malignant tissue is essentially immortal because it has its own supply and will not age or die, it just keeps growingiii. Malignant tumors can copy the full chromosome and the full length of the telomere, which allows them to never die. 8. Cell Age – cells know how old they are!a. Telomeres allow the cell to know their agei. Every time DNA is copied, the telomere shortens1. Once the telomere is gone the cell dies. Epithelial Tissues1. Definition: Epithelial tissue covers or lines other tissues. It is the lining of cavities, organs, skin, etc. The tissue sits on a layer of fibers called the basement membrane, which is used to separate the epithelial tissue from the tissue beneath it which is almost always connective tissue. The top of the epithelial cell is the apex, which faces the lumen (emptiness).a. Sits on the basement membrane, has numerous cell to cell junctions, has a high rate of mitosis, has sparse blood supply, and it lines the lumen of viscera (organs)2. Junctions: used to hold the cells togethera. Tight junction – a really tight junction that causes cells to fuse together to make it impermeable. This is used to protecti. Membranes bound tightly together by transmembrane proteins, isolates waste in the lumen; prevents passage of water and solutesb. Gap junction – little pores that line up perfectly with other pores to create a tunnel between cells. This is used for communication between the cells i. These only occur on the side, not the apex or base. ii. Cells that don’t need to communicate don’t have theseiii. Embryos have a ton of gap junctionsiv. Transport proteins (connexons) allow for the movement of ions from cell to cell (coordinate contractions in heart muscle)c. Spot Desmosomes – the tissues interlink like they are holding hands to form a strong junction between two cells. i. CAMs and proteoglycans link the plasma membranes; allows bending and twistingd. Hemidesmosome – occurs at the base of an epithelial cells, it is used to anchor the cell to the basement membranei. Attaches a cell to the extracellular filaments in the basal lamina; stabilizes position and anchors to underlying tissue.3. Classifying epithelia: describe them by their shape and number of layersa. simple squamous epithelium: one layer of cells that are wider than they are talli. convenient for places that need diffusionii. blood vessels, capillaries – allow gas exchangeb. simple cuboidal epithelium: one layer of cells that are squarei. Too thick for diffusion, not thick enough for wear and tearii. Great for ducts of a gland, found in kidneys!c. simple columnar epithelium: one layer of cells that are taller than