BSC 2010 Review Sheet – Chapter 12 and 13 last updated Spring 2014 Chromosomes and Cell Division 1. For what reason(s) do cells of single celled organisms divide? How about multicellular organisms? What type of cell division is involved in each case? -Single celled organisms: one reason is reproduction -binary fission – “division in half” -copied by DNA replication -For multicellular organisms, cells divide for: 1. Growth/development, 2. Repair/regeneration, 3. Reproduction -mitosis: (division of the nucleus) IDENTICAL; for growth, repair. Occurs at end of cell cycle. Occurs in somatic cells -somatic cells – body cells…not including sperm and eggs (gametes) -meiosis: ½ the number of chromosomes; reproduction…gametes…yields nonidentical daughter cells that have only one set of chromosomes (occurs only in gonads – overies/testes) 2. Summarize what occurs during each of the 4 phases of the cell cycle . What is G 0 phase? At what point of the cycle can cells ‘decide’ to enter G 0 ? -cell cycle – tightly regulated series of events, unique to euks. (process controlled by many enzymes) -Four stages of the cell cycle: mitotic M phase, G1 phase (first gap), S phase (synthesis), and G2 phase (second gap). -Mitotic M phase: where cell division occurs; includes both mitosis and cytokinesis; shortest part of cell cycle (less than 1 hour) -Interphase: about 90%; longest phase; cell grows by producing proteins and cytoplasmic organelles -G1 phase: growth/prep for S phase (5-6 hrs) -S phase: chromosome duplication; DNA synthesis (10-12 hours) -G2 phase: more growth/prep for M phase (4-6 hrs) -Cells can leave the cell cycle, and enter a non-dividing state = G o phase (if it does not receive go-ahead signal at G1 phase) 3. Explain how the frequency of cell division varies in the tissues of an adult multicellular organism. How does G 0 phase fit in? Give examples of human cell types from lecture. -Frequency of mitosis depends on cell type. -some cells divide continuously (GI tract, blood cells, skills) -some cells divide based on need (liver – detoxification) -some cells rarely/never divide (neurons, CNS/PNS, muscle) -G o applies to “based on need” and “rare/never” -Most human cells are in G o 4. The terms gene , genome , DNA , chromosome , replicated chromosome , sister chromatids , and chromatin are distinct ways of referring to genetic material. What does each term mean? How do terms relate to one another other? Compose sentences such as “_____ is
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