Cell Cycle Notes --PreAP

Transcription

1 Cell Cycle Notes --PreAP I. DNA Deoxyribonucleic acid; located in nucleus A. Long and thread-like DNA in a non-dividing cell B. Thick, short, coiled doubled DNA in a dividing cell chromosome 1. chromosome consists of 2 parts: a. chromatid b. centromere protein tab holds 2 sister chromatids together 2. are divided into segments called genes C. Illustration: to duplicates itself coils up into chromosome II. Cell Cycle the repeating sequence of growth and division of a eukaryotic cell A. The cell spends most of its time in 1. cell grows, DNA is loosely wound, and cell carries out normal functions 2. 3 phases: a. cell grows and matures G1 (first growth) b. duplicates S (synthesis) G1 phase c. organelles replicate and cell prepares for division G2 (second growth) S phase B. Division of the nucleus mitosis C. Division of the cytoplasm and organelles cytokinesis Occurs quickly 1. In animal cells the cytoplasm pinches in G2 phase 2. In plant cells a cell plate forms D. After mitosis and cytokinesis, the cell returns to cell plate

2 III. Mitosis division of the nucleus into 2 nuclei, each with the same number and kind of A. HANDOUT B. 4 phases PMAT 1. condense, nuclear envelope breaks down, spindle fibers form Prophase 2. line up along equator Metaphase 3. chromatids separate, centromere divides, and move to opposite poles Anaphase 4. uncoil, new nuclear envelope forms, spindle fibers break down Telophase C. Mitosis occurs only in body cells, or somatic cells D. 2 new cells formed have same number and kind of as original 1. original cell called parent cell 2. cells formed are known as daughter cells Parent Cell 2 Daughter Cells E. Many organisms, especially unicellular organisms, reproduce by means of cell division--- called asexual reproduction ex: bacteria F. Chromosome Number 1. number of each organism has in its cells varies from species to species example: human = 46 lettuce = 18 dog = 78 gorilla, chimp = all cells (except the sex cells) in an organism have the same number of example: human = 46 skin cells = 46 muscle cells = 46 cardiac (heart) cells = 46 G. Regulating the Cell Cycle not all cells move through cell cycle at the same rate 1. in eukaryotic cells, timing of the cell cycle is regulated by proteins called cyclins a. cyclins initiate the various stages of cell cycle 2. cell cycle checkpoints -- regulate progress of cell cycle a. ensure that damaged DNA not passed on to daughter cells b. G1 checkpoint at end of G1 phase -- determines whether cell is ready to divide or not c. G2 checkpoint at end of G2 phase check to make sure DNA replication is complete d. M checkpoint at Metaphase check for whether properly attached to spindle fibers 3. injuries affect rate of cell division a. cells at edge of injury stimulated to divide rapidly -- producing new cells b. when healing is completed, rate of cell division -- slows down and returns to normal 4. when cells come into contact with each other in culture, they stop dividing

3 H. Uncontrolled Cell Growth 1. control over cell cycle can break down resulting in -- cancer 2. cancer cells do not respond normally to signals that regulate cell division 3. cells divide uncontrollably forming -- tumors and can invade other tissues 4. mutations in DNA leading to tumors can be caused by: a. chemicals smoking or asbestos (lung cancer) b. radiation sun -- UV rays (skin cancer) c. viruses HPV (cervical cancer) or hepatitis (liver cancer) d. immune system disorders HIV (many different cancers) e. heredity genetics 5. p53 guardian of the genome a. plays role in triggering control mechanisms at checkpoints -- suppresses tumors to prevent cancer b. p53 can either repair faulty DNA or kill off cell if it can t be repaired (apoptosis) c. problems with gene p53 -- related to more than 50% of all cancers

4 Cell Cycle Mitosis (p text) Prophase duplicated spindle fibers form nuclear envelope breaking apart Metaphase (middle) spindle fibers centrioles nuclear envelope centriole Anaphase (away) Individual Cytokinesis Telophase (two) nuclear envelope reforming unwind into

5 Complete for review: Phase Chromosome Appearance and/or Location Important Events DNA/ copies itself DNA Replication Cell grows and replicates organelles Prophase Chromosomes coil up Nuclear envelope disappears Spindle fibers form Metaphase Chromosomes lineup in the middle Spindle fibers connect to Anaphase Chromosome copies divide and move apart Spindle fibers pull chromosome copies apart to opposite poles Telophase Chromosomes uncoil back into Nuclear envelopes reform 2 new nuclei are formed Spindle fibers disappear Cytokinesis Chromatin Division of the rest of cell s cytoplasm and organelles