Biol 101 1st EditionExam #2 Study Guide Lectures 13-22Lecture 13 (October 1)What type of cell division occurs in Eukaryotic cells? Prokaryotic?Eukaryotic cells divide via mitosis (somatic cells) or meiosis (production of gametes). Prokaryotic cells divide by Binary fission. Binary fission is the process in which the DNA is copied and is thenseparated into 2 daughter cells. Mitochondria and chloroplasts divide the same way.What are three functions of mitosis? Where does it occur?Three functions of mitosis are growth, repair/replacement, and asexual reproduction. Mitosis occurs in somatic cells, which are any cells that are not gametesDescribe what happens during each of the three divisions of InterphaseThe three phases are Gap 1, S, and Gap 2. In G1, cell growth, duplication of organelles, and the preparation for DNA replication occur. In S, DNA synthesis/replication occurs. In G2, more growth occurs, centrosomes appear, and the cell prepares to divide.Explain each step of MitosisThere are 4 main stages in mitosis: prophase, metaphase, anaphase, and telophase/cytokinesis. In Prophase, the nuclear envelope disappears, the golgi and ER degrade, chromosomes condense, centrosomes (organize microtubules) migrate to opposite sides of the cell, and the mitotic spindle forms. InMetaphase, chromosomes align on the metaphase plate, in which a sister chromatid is on each side of the plate. In Anaphase, cohesis degrades, the kinetochore microtubules get shorter (siter chromatids split), the nonkinetochore microtubules get longer (elongating the cell). Telophase is the opposite of prophase, with that being said, the nuclear envelope, golgi and ER reform, chromosomes dedense, centrosomes disappear, and the mitotic spindle breaks down.What are organisms considered when they have paired chromosomes? Unpaired?If the organism has paired chromosomes, they are considered Diploid (2n). One chromosome comes from the mother, the other from the father. If the organism has unpaired chromosomes, they are considered Haploid (1n or n).Define a centromere, kinetochore, and cohesionA centromere is the center region where sister chromatids attach. Cohesions are protein complexes that regulate the separation of sister chromatids during cell division (located along length. Kinetochores are located on either side of the centromere; these are protein structures where themicrotubules attach during mitosis.Lecture 14 (October 3)What is the cell cycle control?There are checkpoints in each cell that are regulated by regulatorymolecules which decided whether division should continue or not (G1 and G2 checkpoints). In the G1 checkpoint, the cell gets the signal to divide, the cell checks to make sure that a growth factor is present, or if the cell is big enough. The gate will go down forthe checkpoint, and when all is okay, the DNA will be checked to make sure it is undamaged. In G2, the checkpoint makes sure that DNA replication is complete. In the metaphase checkpoint, chromosomes are checked to make sure they are attached to the kinetochore microtubules.What happens in normal cell division?If a problem is spotted, it is fixed and cell division continues. If the problem can't be fixed, apotosis, or cell suicide occurs. In apotosis,the cell DNA is degraded, the cell blebs apart and dies, and the remnants are engulfed by other cellsWhat are the properties of normal cells?The cells need a growth factor to be present to stimulate cells to divide (start and stop reproducing at the right time), exhibit anchorage dependence (must be touching some kind of surface in order to divide, usually and extracellular matrix), and must exhibit density-dependent inhibition (cell stops dividing at critical density).What are the properties of cancer cells?The problem doesn't get fixed and the cell goes past the checkpoint, in which cells proliferate a form a tumor; the cells become immortal at this point. The tumor grows from a single cancer cell and invades neighboring tissue. These cells are dividinguncontrollably which from a benign tumor (essentially not cancerous). The cancer cells will then spread to another part of the body via metastisis (part of the tumor breaks off and goes intoblood, anchorage-dependence is ignored). The tumor becomes malignant, or cancerous. Cancer cells can then survive and establish a new tumor in another part of the body.How does an external signal regulate cell division?This occurs via signal transduction (getting your message across the membrane). First, reception is when the signal binds to the receptor (activated shape change in receptor). Next, transduction occurs which converts the external signal to an internal message. This occurs via phosphorylation in which P from ATP changes the shape. This replays molecules in the signal transduction pathway. Finally, a response occurs in which the active cell cycle control proteins or turns on cell cycle control genes in a regulation of cell division.How does a proto-oncogene become an oncogene?Point mutations and gene amplification are to blame. In point mutations, the protein folds abnormally which activates the cell allthe time; this leads to a resistant protein. In gene amplification, normal growth stimulates protein in excess. Here, gene copies increase, mRNA transcription increases, number of surface receptors increase, and the rate of cell division increases. Tumor suppressor proteins are available to shut down cell division if conditions are not favorable at the checkpoints. These proteins will detect and/or repair the damaged DNA, promote apotosis anddensity-dependent inhibition. This protein can become mutated, however, which means the cell cycle checkpoints will be ignored and damaged calls will proliferate. Tumor suppressors can also be silenced by aberrant methylation, an epigenetic phenomenon. Methyl groups on a gene increase, which in turn shut a gene off and causes the tumor suppressor not to be made.Lecture 15 (October 6)What is the sexual life cycle of animals?Gamete formation occurs in meiosis, then fertilization (union ofgametes- 2n zygote → fertilized egg), and finally growth development via mitosis.What is meiosis and what are its phases?Meiosis is the cycle in which only sex cells go through. The daughter cells are not identical to parent cell or each other. In females the chromosomes are XX and in males, XY. These cells only go through the cycle once, there is no division past the meiosis cycle. In Prophase 1, Chromosomes condense,
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