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Biol 121- 2010.01.22- Genetics- DNA, Cell Cycle (Ch. 14, Ch. 11).docx

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Applied Biology
APBI 200
Paul Hewitt

Biol 121 225 Freeman 295-302, 222-7 Jan 21, 10 DNA – Ch. 14 Strain and virulence -a strain is a population of genetically identical individuals -strains that affect humans vary in their virulence – their ability to cause disease and death -virulent strains cause disease, avirulent (benign) strains do not Medium -a liquid or solid that is suitable for growing cells (a petri dish can contain nutrient-containing medium) Griffith and transformation -Griffith in the 1920s did experiments to develop vaccine against Streptococcus -Experiment pneumoniae bacterium -Griffith worked with strains identifiable by eye when grown on a nutrient- containing medium in a petri dish -on a solid medium, cells from the nonvirulent strain form colonies that look rough (R) ; cells from the virulent strain form colonies that look smooth (S) -Setup -Griffith injected mice with R strain, S strain, heat-killed S strain, and R strain with heat-killed S strain -Results and Conclusion -found that mice died when injected with S strain, and with R strain with heat- killed S strain; mice did not die with R strain nor heat-killed S strain -Griffith proposed that something from the heat-killed S cells “transformed” the nonvirulent R cells Culture -a collection of cells that grows under controlled conditions – usually suspended in a liquid medium or on the surface of a solid growth medium Hersey-Chase experiment – were -study how a virus called T2 infects Escherichia coli genes made of protein or DNA? -T2 infections begin when viruses attached to cell wall of E. Coli and injects -Background info genes -genes then direct the production of a new generation of virus particles inside the infected cell, which acts as a host for the parasitic virus -during infection, protein coat of original parent virus left behind Two important facts of their strategy -proteins present in T2 contain sulphur but not phosphorus; DNA contains phosphorus but not sulphur Experimental setup -grow viruses in presence of P-32 which will then have viral DNA, and some viruses in presence of S-35 which will then have viral protein -allow viruses with labelled DNA to infect one culture of E. Coli cells and viruses with labelled protein to infect another -agitate cultures in kitchen blender to separate empty viral protein coats from bacterial cells in each culture -centrifuge solutions of bacterial cells from each culture to force cells into a pellet, record location of radioactive labels Hypotheses -DNA hypothesis: radioactive DNA located within pellet -protein hypothesis: radioactive protein will be located within pellet Results -radioactive DNA is in pellet, radioactive protein is in solution DNA – polymer/monomer? -DNA is a long, linear polymer made up of monomers called deoxyribonucleotides -Components of the monomer of DNA, -deoxyribonucleotides consist of a deoxyribose (sugar) mcule, a phosphate polymerization/direction group, and a nitrogenous base -deoxyribonucleotides link together into a polymer when a phosphodiester Biol 121 225 Freeman 295-302, 222-7 Jan 21, 10 bond forms between a hydroxyl group on the 3’ carbon of deoxyribose and the phosphate group attached to the 5’ carbon of deoxyibose Double helix and its formation -two individual DNA single strands will run alongside in opposite direction – antiparallel fashion -the antiparallel strands will twist around each other into a spiral or helix because certain of the nitrogen-containing base fit together in pairs inside the spiral and form hydrogen bonds Interactions in the double helix -the reason for the double helix are the hydrogen bonds between bases as well as stacking interactions (van der Waals forces or hydrophobic interactions) -complementary base pairing discusses the specific pairing rules for hydrogen bonding of nitrogen-containing bases (A to T, C to G) DNA is semiconservative (DNA -the three main theories of DNA replication were conservative, replication) semiconservative and dispersive models -semiconservative means that each newly made DNA mcule comprises one old strand and one new strand DNA synthesis direction (replication) -DNA monomers (deoxyribonucleotide triphosphate - dNTP) are added to the 3’ end of the strand and a phosphodiester bond is formed (5’  3’) The Cell Cycle – Ch. 11 Cell theory -all organisms are made of cells and cells arise from pre-existing cells -how do new cells arise from pre- -cell division existing cells? Chromosomes are the carriers... -are the carriers of hereditary material – the instructions for building and operating the cell Two types of nuclei division -leads to production of sperm and eggs; the other type of nuclear division leads to production of all other cell ty
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