Biology 1201 - Exam 3-1

Biology 1201 - Exam 3-1 - Tuesday March 3 2009 Growth...

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Tuesday, March 3, 2009 Cells need to possess the genetic material characteristic of the organism o Genetic material is DNA o The “daughter” cells need the complete genetic complement The genetic material of prokaryotes is: Circular DNA Prokaryotes o Circular strands of DNA o o Divide by binary fission Figure 12.11 DNA can attach to plasma membrane to duplicate itself & attach the two strands of DNA to different ends of the plasma membrane & the cells can grow & separate Eukaryotes o A problem o Genetic material is found in linear chromosomes Linear strands of DNA complexed with proteins Multiple chromosomes (example: humans 46) How to insure that each daughter cell gets the complete set of chromosomes? How do you get identical daughter cells? Need a mechanism to allow each daughter cell to have a copy of the solution - A process called mitosis Cell Division: Mitosis o Reproduction o Growth o Repair o Produce “daughter” cells that have identical genetic complements o Occurs in somatic cells Somatic Cells o All body cells except cells which give rise to gametes (eggs Chromosomes o o Each eukaryotic species has a characteristic number o Found in the nucleus
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Chromatin o Duplicated chromosome o Consists of two sister chromatids o Identical copies of DNA o Attached at a specialized region called the centromere Figure 12.4 How many centromeres per chromosome? 1 How many centromeres per chromosome consisting of 2 sister chromatids? 1 Figure 12.5 Cell Cycle o Interphase o Miotic phase Mitosis Cytokinesis Interphase o Generally 90% of the cell cycle o Gap 1 (G1 Phase) o S Phase (DNA is synthesized/replicated) o Gap 2(G2) o Gap 1 Synthesis of cell components Increase in number of organelles o S Phase Synthesis (replication) of DNA Doubling of the genetic material o Gap 2 Centrioles replicate in animal cells Structure for cytokinesis put in place What does a centriole resemble? The base of a flagellum Figure 6.24 Centrioles o In animals o 9 sets of triplet microtubules arranged in a ring o Found in the centrosome A region which microtubules grow out o Help organize microtubule growth, but centrioles are not necessary
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Most plants lack centrioles Figure 6.22 The purpose of mitosis is to insure that daughter cells have the identical genetic complement of the mother cell. True DNA is replicated in: S Phase Mitosis o Prophase o Prometaphase o Metaphase o Anaphase o Telophase Prophase o Nucleoli disappear o Chromatin condenses o Mitotic spindle forms from microtubules in cytoplasm o Centrosomes move away from each other Prometaphase o Nuclear envelope fragments o Microtubules of spindle invade the nuclear region & interact
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Biology 1201 - Exam 3-1 - Tuesday March 3 2009 Growth...

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