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Biol 120_Molecular Biology (Lecture notes__2012-2013T1)(1).doc

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BIOL 120
Yangdong Wei

Biology 120302Biology 120302Text book Brooker et al BiologyText book Brooker et al Biology2010 Canadian Edition2010 Canadian EditionGenetics Chapter 15Genetics Chapter 15Historical PatternsHistorical PatternsMendels PrinciplesMendels PrinciplesThe Chromosomal Basis of InheritanceThe Chromosomal Basis of InheritanceMolecular BiologyChapters 10111213Molecular BiologyChapters 10111213The Genetic MaterialThe Genetic MaterialDNA ReplicationDNA ReplicationThe Flow of Genetic Information Gene ExpressionThe Flow of Genetic Information Gene ExpressionThe Control of Gene ExpressionThe Control of Gene ExpressionBiotechnologyGenome Chapters 1819BiotechnologyGenome Chapters 1819Bioenergetics Chapter 6 7 8 9Bioenergetics Chapter 6 7 8 9Review of the Working CellReview of the Working CellCellular RespirationCellular RespirationPhotosynthesisPhotosynthesis4The Genetic Material4The Genetic MaterialCharacteristics of the genetic materialReplicationStorage of informationExpression of that informationVariation by mutationDiscovery of DNA as the genetic materialHistorical accountEarly studies had indicated that the genetic material resides in the nucleusWhen nucleus was stained with specific dyes it was shown to consist of proteins and nucleic acidsUntil the 1940s many geneticists favored proteinsAbundantMany formsEvidence favoring DNAIn body cells the amount of DNA was constant However in gametes it was reduced to 1Experiments confirm DNA as the genetic materialIProkaryotic bacterium transformationFrederick Griffiths experiment 19271928a bacterium that is a causing agent Two strains of the bacterium Streptococcus pneumoniaeof the lung disease pneumonia were used to inject laboratory miceA smoothS strainvirulentmice diedA roughR strainnonvirulentmice survivedThe S strain has a polysaccharide coat that protects bacteria from the hosts defense system The R strain lacks this coat and will be destroyed by the host defenseIn Griffiths experimentsHeatkilled injectionmice livedS bacteriaHeat killed S bacteria R bacteriainjectionmice diedWhen Griffith examined the blood of the dead mice they had the S bacteriaGriffith suggested that R bacteria had been transformed with the genetic material from S bacteria The genetic material from S bacteria had converted the nonvirulence avirulent to the virulenceIt was not until 1944 that Oswald Avery et al at the Rockefeller University identified the substance as DNAThey purified DNA from S bacteria and transferred it to R bacteria which converted R bacteria to be virulentThese experiments first established that DNA is the genetic material in cellsIIBacteriophage infectionThe HersheyChase experiments 1952These experiments conducted by A Hershey and M Chase at the Carnegie labs provided much more of convincing evidenceThey used a virus T that infects bacteria The virus has a simple structure that consists of an 2outer protein coat and has the DNA inside the coat32Hershey and Chase fed T infected bacteria with radioactive compounds P phosphorus 235 and Ssulfur and incorporated them into viral DNA and protein respectively2
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