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UNIT 1 SELF NOTES.docx

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Department
Biology
Course
BIO1140
Professor
A L L
Semester
Winter

Description
UNIT 1STRUCTUREDNA vs RNADNA has thymine which has a methyl group while RNA has Uracil no methyl groupDNA has a ribose H RNA has a deoxyribose OHFunction of protein in DNA to neutralize the negative charge caused by a negative phosphate backboneFrederick Griffith ExperimentHe worked with two forms of Streptococcus pneumoniae The smooth strainShas a polysaccharide capsule surrounding each cell and is virulent The rough strainRdoes not have a polysaccharide capsuleand is nonvirulent Therefore the capsule is responsible for the virulence of the S strain killed S bacteria and injected into mice they livedheatkilled S and live R forms mixed together and injected into mice the mice died Therefore the live R forms must have been transformed into S forms by acquiring the ability to make a polysaccharide capsuleLater it was found out by Oswald Avery that DNA was the transforming agentHe used the same bacteria as Griffith and mixed heatkilled S forms with R form Then when he killed off protein or RNA in the cells the R form was still being transformed into S form This meant that DNA was the transforming agentHershey and ChaseThey worked with bacteriophages viruses that infect cells because a virus has DNARNA inside its protein coat They tagged DNA and the protein separately with radioactive labelsDNA entered the cellsProtein coat remained on outsideTherefore DNA was the transforming agent Watson and CrickDNA contains 4 nucleotides ATGCDNA ismade of 5 carbon sugar deoxyribosephosphate group 1 of the four nitrogenous basesATGCA and G are purines 2 ringsT and C are pyrimidines 1 ringpurines bind with pyrimidines AT GC via hydrogen bondingErwin ChargaffAT GC DNA has a sugarphosphate backbone because the nucleotides in one strand polynucleotide are joined by phosphates 5 endphosphate group 3endhydroxyl group strands are antiparallel Rosalind Franklinused xray diffraction to determine that the DNA has a helical structure She could also tell the the DNA is 2nm in diameter and patterns of atom repeats occurred every 034 nm 1 base pair and 34 1 full helix turn nm in lengthHowever she did not have crystals to work with which would have made her results more accurate Meselson and StahlDNA is semiconservativeProcedure Used heavy nitrogen isotopes to label the parent strands of the DNA They transferred the N15 labeled DNA into a light nitrogen isotope medium N13 so that the newly synthesized DNA strands would incorporate it UNIT21DNAReplicationDNA Polymerase assembles the complementary strands of DNA from individual nucleotides More than one kind of DNA polymerase is required for DNA replication in both eukaryotes and prokaryotes Nucleoside triphosphates nitrogenous basedeoxyribose sugar3phosphatesdATP dGTP dCTPdTTP aresubstrates for DNA polymerase DNA polymerase can only add nucleotides to the 3end therefore the new strand is synthesized in the 5 3 but is read from 35 DNA helicase unwinds the DNA by using energy from ATP hydrolysisSinglestranded binding proteins stabilize the DNA for replication so that the unwound DNA does not twist back together Topoisomerase prevents the DNA from overtwistingPrimase lays on the primer so that DNA polymerase can begin synthesis Later the primer is removed and replaced by DNA Leading Strand is synthesized continuously in the direction of unwindingLagging Strand is synthesized discontinuously in okazaki fragments DNA Polymerase I removes the RNA primerDNA Ligase joins the space between okazaki fragments and closes the nicks
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