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DNA StructureDouble strandedNucleotide
Nitrogen BasesSugarPhosphate
Base PairsHydrogen Bonds
A-TC-G
Alpha helix5’ – phosphate group3’ – hydroxyl group
RNA StructureSingle strandNucleotide
Nitrogen baseSugarPhosphate
Base PairsA-UC-G
Three typesmRNArRNAtRNA
Prokaryotic ChromosomesLocation
Nucleoid regionNo membrane
NumberMost have 1Some species have 2, the second linear
AppearanceCircularDsLoops and coils
DNA ReplicationSemiconservative
Replication forkSingle originBidirectional
2 Leading strands2 Lagging strands
EnzymesHelicasesDNA polymerases 5’ to 3’
I for leading strandII digest RNA primerIII for lagging strand
DNA ligaseDNA gyrase
Hydrogen bonds broken and reformedMethylation of adenine bases
Initiation sitesTurn on or Turn off Protect against viral infectionsDNA repair
Polymerase I & II
Plasmids
2% of genetic informationDs, circular extra chromosomal DNAIndependent replicationCellular Traits
F-FertilityR-Resistance : inactivate AB, toxins, heavy metals Dissimilation: catabolism of unusual substancesBacteriocinsVirulence : enzymes, toxins, attachment
Rolling Method for DNA replication and F-Plasmid
Rolling MethodOne strand remains in loopSecond strand breaks away and rolls of loopBoth strands serve as templates for daughter strandOccurs during conjugation
TranscriptionDNA RNA
mRNArRNAtRNA
Initiation Sigma factor on RNA polymerase
binds to promoter sequence on DNAWill be release after 10 nucleotides
RNA polymeraseunzips, unwinds DNALacks proof reading ability
Elongation 5’ to 3’, slower
Ribonucleotide sequencesBase pairs :
A-U [instead of Thymine] C-G
TerminationSelf
Terminator sequenceG-C rich area
Protein-dependantTerminator proteinSeparates DNA and RNA polymerase
Prokaryotic RNATranscription = RNA PolypeptidesRNA
mRNACode for several polypeptides along strandEach code has codons: Start and Stop
tRNAAcceptor stemAnticodonWobble
rRNA70S Ribosomes
50S: 23S + 5S rRNA and 33 proteins30S: 16S rRNA and 21 proteins
Binding Sites on RibosomesA: accepts tRNA with AAP: holds tRNA for base pairing anticodon to mRNA codon for polypeptideE: release [exit] for tRNA
Translation StepsInitiation
30StRNA @ P site50SGTP used
ElongationNew tRNA @ A siteRibozyme in 50S forms peptide bondGTP used
TerminationRelease factor proteinsStop codon on mRNA
Regulation of Gene ExpressionConstitutive
Not regulatedAlways “on” at fixed rate
TranscriptionTranslation
60-80%Polypeptides need in large amounts
RegulatedOnly when neededControl synthesis of enzyme : genetic control
InductionRepression
Control enzyme activity: feedbackNoncompetitive inhibitionCompetitive inhibition
Genetic Control of Enzyme Synthesis and formation
Operon ModelOperator (O)Promoter (P)Structural genes
Regulatory genesMakes repressor
Active binds to OInactive unable to bind to O
TypesInducible Operons
Repressor ActiveOperon OffInducer needed
Repressible OperonsRepressor inactiveOperon OnCorepressor needed
MutationsDefineTypes
SilentPoint
Mis-senseNon-senseSense [aka silent]
Substitution Transition: purine for purineTransversion: purine for pyrimadine
FrameshiftInsertionsDeletions
CausesSpontaneousInduced
ChemicalPhysical
ConditionalAdaptiveTransposons Thymine dimer
inversion
Genetic TransferVertical
Parent to offspring
HorizontalLateral transfer to same generationDonor to recipientDNA transferPlasmid transferTypes
TransformationTransductionConjugation
TransformationOccurance
1%RandomNaturally in certain species
HaemophilusNeisseriaPseudomonasStreptococcusStaphylococcus
Griffith experimentGenetic transfer
Environment Competent cells
Cell wallPlasma membrane
Bacterial lysisDNAPlasmids
Transduction
Transfer of bacterial genes via virusesDonor to recipientVirus: Bacteriophages
Types GeneralizedSpecialized
Replication CycleLyticLysogenic
Specialized Lysogenic CycleOnly certain bacterial genes are transferredExample: Toxins
CorynebacteriumDiphtheria toxin
Streptococcus pyogenes
Erythrogenic toxinE. coli
Shiga-like toxin
Conjugation
DefineBacteria
Gram Neg : F.pilusGram Pos: sticky surface molecules
TypesF+ [plasmid]R [plasmid]Hfr [DNA]
Genetic Recombination
GeneralHomologous chromosomesAny locationDNA breakage and repair
Site SpecificNonhomologousViral genomes in bacterial chromosomes
Replicative
Genetic EngineeringUse
PlasmidsRecombinant DNA
ApplicationsTherapeutic
HormonesEnzymesVaccinesGene therapy
AgriculturalScientific
Southern BlotELISA tests