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Cell Cycle Notes -- PreAP I. DNA – A. Long and thread-like DNA in a non-dividing cell – B. Thick, short, coiled doubled DNA in a dividing cell – 1. chromosome consists of 2 parts: a. b. 2. chromosomes are divided into segments called – C. Illustration: chromatin to chromosomes 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 phase b. chromatin duplicates – c. organelles replicate and cell prepares for division – S phase G2 phase B. Division of the nucleus – C. Division of the cytoplasm and organelles – Occurs quickly 1. In animal cells the cytoplasm pinches in 2. In plant cells a cell plate forms D. After mitosis and cytokinesis, the cell returns to Interphase III. Mitosis – division of the nucleus into 2 nuclei, each with the same number and kind of chromosomes A. HANDOUT B. 4 phases 1. chromosomes condense, nuclear envelope breaks down, spindle fibers form – 2. chromosomes line up along equator – 3. chromatids separate, centromere divides, and move to opposite poles – 4. chromosomes uncoil, new nuclear envelope forms, spindle fibers break down – C. Mitosis occurs only in body cells, or – D. 2 new cells formed have same number and kind of chromosomes as original 1. original cell called – 2. cells formed are known as – Parent Cell E. Many organisms, especially unicellular organisms, reproduce by means of cell division--called F. Chromosome Number 1. number of chromosomes each organism has in its cells varies from species to species example: 2. all cells (except the sex cells) in an organism have the same number of chromosomes example: 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 – a. cyclins initiate the various stages of cell cycle 2. cell cycle checkpoints -a. ensure that damaged DNA not passed on to daughter cells b. G1 checkpoint at end of G1 phase -c. G2 checkpoint at end of G2 phase – d. M checkpoint at Metaphase -3. injuries affect rate of cell division a. cells at edge of injury stimulated to divide rapidly -b. when healing is completed, rate of cell division – 4. when cells come into contact with each other in, culture they stop dividing 2 Daughter Cells H. Uncontrolled Cell Growth 1. control over cell cycle can break down resulting in -2. cancer cells do not respond normally to – 3. cells divide uncontrollably forming -4. mutations in DNA leading to tumors can be caused by: a. chemicals – b. radiation – c. viruses – d. immune system disorders – e. heredity – 5. p53 – “ guardian of the genome” a. plays role in triggering control mechanisms at checkpoints -b. p53 can either – or – c. problems with gene p53 -- Cell Cycle – Mitosis (p.246-247 text) Complete for review: Phase Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Chromosome Appearance and/or Location Important Events