48 Pages

Microbiology and Immunology
Course Code
Microbiology and Immunology 2500A/B

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Kang NotesAn Intro to Molecular BiologyPart 1 GenesWhat is common between almost everything in the world All have nucleic acidVirus some have their genome in the form of RNAAnimal CellGenome that duplicates the cell are all contained in the nucleusHumans have 23 chromosomesHuman Genome Project23 pairs of chromosomes contain DNA33 billion base pairsApproximately 35 000 genesthese are all identifiable genes that can produce proteinsTotal length of DNA1 x 1010 KmTotal length can do 33 round trips to the sun or wound up the earth 250 000 timesGenesCan produce a proteinChromosome has DNADNA carries the geneGene is composed of 4 different basesGGuanineCCytosineAAdenineTThymineor in RNA UUracil instead of thymineMost DNA exist as double stranded formSome viruses exist as single stranded formsGA have hydrogen bonds that bind themCT have 2 hydrogen bonds that bind themGroups are bound in chains by sugar phosphate groupsDNA replicates semiconservativelyOnly replicates in one direction from 3 to 5In order to copy DNA has to unwind then one strand goes up and another strand goes down bc it only copies from 3 to 5 directionProduct is 5 to 3 replicate opposite bind opposite directionPathway of Information Flow in DNA Virus ReplicationDNA can exist as dsDNA or ssDNAssDNA has to go through dsDNA intermediate to make more ssDNAaka virusIn cell dsDNA is transcribed to make mRNA which is translated to make a proteinViruses are either ssDNA or dsDNAClassification of RNA Virus GenomesSingleStranded RNA VirusesPositive sense RNA virusescan be translated to make proteinsNegative sense RNA virusescomplementary to the positive senseAmbisense RNA virusescontains both positivenegative senseDoubleStranded RNA VirusesSome small group of viruses contain dsRNAPathways of Information Flow of RNA VirusesIn order to make a protein negative ssRNA you have to make complementary positive ssRNA which can then be translated from positive ssRNA Normal cells dont hold RNA dependent RNA polymeraseunique to RNA viruses not in the normal cells WILL ASK THIS QUESTIONIf is positive ssRNA it can be translated right awaytherefore doesnt have to carry RNA polymerase in virus particles bc as they get into cells they can translate genomic RNA to become RNA polymerase few exceptions but this happens in most casesssRNA virus makes mRNA positive which can be translated to make proteinssRNA positive make dsRNA as intermediateOne unique RNA virus called retrovirus which is positive ssRNA virus but makes DNA intermediate during replication of this virus One that goes through DNA intermediate is retrovirusmakes DNA with RNA they carryReverse transcriptase containing virus aka is positive ssRNA that contains RNA polymeraseNegative ssRNA viruses must make messenger RNA therefore they have to carry RNA polymeraseIf positive ssRNA can be translated as they get into the celltherefore dont need to carry enzyme into particles Types of MutationSeveral types of mutations Deletion of chromosome section of DNA thats deletedDuplication of chromosome section of DNA thats duplicatedInversion of chromosome section thats taken outturned aroundInsertion Insertion of extra chromosomeTranslocation Some of these mutations can give different types of diseasesPart 2 Expression of GenesEither DNA or RNA has to be expressed to make proteinsAnimal cellgene expression takes place in nucleusThe Central Dogma of Molecular BiologyUnidirectional information flowBefore discovery of enzyme that converts DNA back to RNA was unidirectional flow therefore have DNA to RNA to proteinunidirectional information flow in this biological systemDNA exists as dsDNAis trying to transcribe to make mRNA mRNA is transported from nucleus to cytoplasm which is then translated to make a proteinExceptionReverse transcription by RNA dependent DNA polymerase reverse transcriptaseRNADNAException of the unidirectional information flowdiscovery of this enzyme changed the central dogma discovered in 1970DNA is Made Up OfEitherRNAribonucleic acidDNAdeoxyribonucleic acidNitrogenous bases Sugar phosphate backboneBase pairUracil RNABasic difference between RNADNA is U baseMethyl group from T is now hydrogen on UDeoxyribose from T is now only ribose on UTranscriptionTranscription takes place in the nucleuscan be transcribed from promoter DNA contains promoter sigma factor governs the transcription of these DNAInitially RNA is made out of DNAUnwinding of DNAone of the strands is copied to make transcriptionInitiation Elongation Termination5 7mG Cappingprotected 5 end3 polyadenylationadding the adenineAll eukaryotic messenger RNAs contain poly A sequence at the 3 endProtects mRNA from the degradation governed by the RNAsmRNA SplicingmRNA are formed cleaved partially to make functional messenger RNANot entire mRNA is translatedIntrons are put togetherexons are put together as functional mRNAmRNA is spliced so caps1 is exons2a1 are put together to make functional mRNASplicing just takes out parts of mRNA we dont want to translatepart used for functional mRNA is exonsRNA SynthesisProcessing3 necessary steps to make a functional mRNA from transcriptswhat are the post transcriptional modifications
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