Bacterial Genetics Flashcards
type of DNA prokaryotes have
haploid (singular circular DNA)
type of DNA eukaryotes have
diploid (chromosomes)
what is an exception for the central dogma
retroviruses contain RNA as their genetic material but make DNA from RNA template by using reverse transcriptase
describe the 4 phases of microbial growth
- lag phase where gene expression is happening
- logarithmic phase/exponential growth
- stationary phase where nutrients are depleting
- decline phase where toxic materials accumulate and cells die
what enzymes are needed for DNA replication in prokaryotes
- dnaA/B proteins
- helicase
- SS binding proteins
- primase
- DNA polymerase
- ligase
- topoisomerase/gyrase
what does dnaA/B do
binds to origin sequence and initiates replication
what does helicase do
separates dsDNA by making ss cuts uses ATP
what do SS binding proteins do
single stranded bidning protein keeps bases unpaired during replication
what does primase do
synthesizes short RNA primers
how many dna polymerases do prokaryotes havw
3
what does ligase do
fills single nucleotide gaps and joins DNA frag together
what does topoisomerase do
removes supercoils from DNA
describe the prokaryotic RNA polymerase holoenzyme
contains 4 subunits with a 5th subunit called sigma factor
what does sigma factor do
recognizes the promoter and helps polymerase bind to DNA
what does polymerase I do
transcribes rRNA genes
where is polymerase I prominent
nucleoli
what does polymerase II do
transcribes mRNA
where is polymerase II prominent
nucleoplasm
what does polymerase III do
transcribes tRNAs and other snRNA
how do prokaryotes initiate transcription
core enzyme and sigma factor bind to promoter
what is unique about the transcription process of prokaryotes?
they are polycistronic where the mRNA codes for multiple proteins
what are the stop codons
- UAA
- UGA
- UAG
what are the start codons?
AUG
moa of aminoglycosides and tetracyclines
block 30s function
moa of chloamphenicol and macrolides
block 50s function
what is diauxic shift
when both energy sources are on a growth plate, so there is a growth curve for both substances
how can bacterial cells use lactose as energy source?
lac operon needs to be expressed as 3 new proteins
what genes does lac operon have on it
lacZ, lacY, lacA
what controls lac operon transcription
lacI
what does lacI encode
lac repressor negatively regulates expression of lac operon genes
what occurs when lac operon encounters lactose?
lactose inactivates lacI repressor so RNA polymerase can bind and activate transcription of the lac operon
what occurs when there is low glucose ?
when glucose low, cAMP is produced. cAMP binds CAP, which then binds DNA. CAP complex helps RNA polymerase bind to promoter = high levels of transcription
what occurs when glucose is high?
no cAMP is made, so CAP cannot bind DNA = low transcription
what is transcriptional attenuation
premature termination under certain circumstances
how do bacteria acquire DNA from other bacteria?
- transformation
- transduction
- conjugation
how do bacteria acquire diversity and virulence?
mutation, recombination, transposition, natural selection,, transduction, conjugation, transformation
what is transformation
uptake of naked DNA
how does transformation happen
- dsDNA binds to cell
- ss DNA moves through cell membrane and into cytoplasm
- new DNA is either kept as plasmid or recombines into host cell DNA
what does transformation require
bacterial competence (state induced in cell allowing it to uptake DNA)
how is a cell made competent?
- naturally
2. in the lab
why are plasmids important
they are carriers of Abx resistance, toxin genes, virulence factors, and antimicrobial agents
what is conjugation?
direct transfer of genetic material between cells via pili
what cells are donors
F+ (encodes conjugal transfer apparatus)
what cells are recipient
F-
what encodes for things necessary for conjugation?
F plasmid has pili and transfer genes
what is the Hfr trait
high frequency recombination where to plasmid may integrate into the chromosomes
what is transduction
transfer of bacterial genes by bacteriophage
what is a bacteriophage
obligate intracellular parasites in bacteria
what is a bacteriophage like extracellularly
they are metabolically inert
what is a M13 bacteriophage
filamentous or helical
what is a omegaX174 bacteriophage
polyhedral or icosahedral
what is a T4 macrophage
polyhedral plus appendage like tails and spikes
describe generalized transduction
any part of the bacterial chromosome can be transduced
what is specialized transduction
only certain special pieces of bacterial chromosome can be transduced
what is phage conversion
when phage carries genes that confer pathogenicity to the bacteria they infect
what bacteria have phage conversion
- corynebacterium diptheriae
- strep pyogenes
- clostidium botulinum
- salmonella
what is a transposon
genetic units capable of mediating their own transfer from one location to another
what is transposition
movement of transposable elements from one location to another on the same chromosome, from one chromosome to another, or between chromosome and plasmid
what are transposases
site specific recombination enzymes
what is transposition related to
multiple drug resistance
