Bacterial genetics Flashcards
(22 cards)
where is a bacterial genetic material found?
in its genome AND in plasmids
what enzyme catalyses the release of supercoiling of DNA?
DNA gyrase and topoisomerase 2
what branch of antibiotics acts as a topoisomerase inhibitor?
Quinolone antibiotics
where does replication of a genome begin?
the ‘origin of replication’ = “oriC”
what enzyme unwinds the DNA to expose single strands of DNA for replication?
helicase
what enzyme is responsilbe for ‘elongation’ phase of replication?
DNA polymerase
DNA polymerase only works in what direction?
5’ to 3’ direction
what enzyme links okazaki fragments/
the DNA ligase
Which enzyme is responsible for proofreading the replication process?
DNA polymerase
what are the four stages of DNA replicaiton?
initiation, elongation, proofreading, and termination
what is the ‘promoter region’ of DNA?
it determines whether a portion of the gene will be read or not
where is transcription initated on a gene?
RNA polymerase binds to the promoter region of the DNA
what is Rifampicin?
it is a RNA synthesis inhibitor - inhibits RNA polymerase and inhibits transcription
what do tRNAs consist of?
anticodon + amino acid required
what is an operon?
it is a length of chromosome that consists of many coordinating genes
so it can transcribe the appropriate proteins all at once - one highway of transcription
describe the ‘lac operon’
only turned ‘on’ when glucose is not present - therefore it utilizes lactose
Lac z = encodes for enzyme beta-galactosidase which converts lactose into clucose and galactose
lac Y and A frunction in transport of lactose into the cell
when glucose is available, the lactose operon is repressed by a protein that inhibits binding of DNA polymerase to the promoter region of the operon
when lactose is higher concentrated than glucose, an ‘inducer’ binds to the repressor, detaching it from the promoter region and making it accessible to the DNA polymerase
what are plasmids? What is their advantage?
they are small circular extrachromosomal DNA molecules that replicate indepedently and can confer phenotypic advantages to the host cell
therefore plasmids can confer multiple antibiotic resistance genes- or virulence genes that give it a selective adaantage
what are the four modes of genetic transfer between bacterial cells?
transformation
conjugation
transduction
transposition
what is the transformation mode of genetic transfer?
DNA fragments are taken up directly by bacterial cells
- either degraded
- or incorporated in the host genome and genetically inherited
*research use plasmid transformation with ‘induced’ methods
What is the conjugation method of DNA transfer>
plasmid transfer between bacterial cells
requires cell-to-cell contact and can occur between different bacterial species and even between gram pos/gram neg. organisms
what is the ‘transduction ‘ method of DNA transfeR?
requires a bacteriophage
- DNA transfer between bacteria via infection with a bacteriophage
phage infects the bacterial cell and replicate
sometimes they incoporate the host genomic DNA into their capsid, so upon infecting another bacteria, they transfer the genetic DNA from the host
what is the ‘transposiiton’ method of DNA transfer?
transposons are DNA sequences that can ‘jump’ within the bacterial genome and from the genome to the plasmids within the same cell - they are mobile genetic elements
in their simplest form they are inserted sequences that carry the enzyme required for their own transposition and are flanked on either side with inverted repeats
