EXAM 1 Bacterial Genetics Flashcards
___ and ___ are coupled in bacteria. what is the result?
- transcription and translation
- the result is the ability to quickly replicate
DtxR regulates ___ genes within ___ operons
- 53
- 26
___ recognize specific promoter sequences and direct the RNA polymerase complex where to bind within the DNA
sigma factors
bacteria contain numerous sigma factors that mediate responses to diverse ___
stresses
how do bacteria change their genetic makeup (how do they evolve)?
- since they are haploid organisms that divide by binary fission, they can’t increase genetic diversity via sex
- options for increasing genetic diversity are mutation or horizontal gene exchange mechanisms
what are 4 main mechanisms of genetic change and diversification in bacteria?
- point mutation
- nucleotide change
- nucleotide insertion
- nucleotide deletion
- gene duplication
- gene deletion
- chromosomal rearrangement
- inversion
- intragenic recombination
during stressful conditions, some bacteria become ___, acquiring mutations at an increased rate
hypermutable
this assures that there are ample variants ready to adapt to new circumstances
describe point mutations
- can impact expression of virulence factors and the sensitivity of antibiotic targets
- antibiotic targets usually come with a fitness cost
gene duplication and amplification constitues an important adaptive mechanism in bacteria. describe.
- resistance to antibiotics like sulphonamide, trimethoprim, and beta-lactams can be conferred by increased gene dosage through duplication/amplification of antibiotic hydrolytic enzymes, target enzymes, or efflux pumps
describe horizontal gene transfer
genes are transferred within a bacterial population
- bacterial transformation - one bacteria releases a piece of its DNA which another bacterium will pick up
- bacterial transduction - bacterial phage infects one bacteria and can package the bacterial DNA; the phage can then go on and infect other bacteria
- bacterial conjugation - some bacteria can use form conjugation bridges to allow the transfer of DNA molecules from the donor bacteria to the recipient
what is transformation?
DNA is taken up directly by cells
bacteria able to take up DNA are said to be ___
competent
some bacteria take up DNA all of the time. they are said to be ___, and express DNA uptake systems.
naturally competent
some bacteria take up DNA mostly from the same genus, requiring what?
specific sequences on the incoming DNA
most naturally competent bacteria take up ___ DNA
linear
describe griffith’s classic 1928 experiment demonstrating natural transformation in strep. pneumoniae
___ is the transfer of DNA mediated by bacteriophages
transduction
transduction is found wherever you find ___
bacteria
in transduction, virus ___ within bacteria
replicate
phages can go through ___ or ___ phases
lytic or lysogenic
___ can carry imporant fitness and virulence determinants
prophage
___ occurs when bacterial genes are packaged by phage and subsequently transferred to other bacteria
transduction
what does conjugation describe?
bacterial sex
what are the 4 plasmid types?
- fertility f-plasmids
- col plasmids
- virulence plasmids
- resistance (R) plasmids
what type of plasmids contain tra genes for transfer, are capable of conjugation, and result in the expression of sex peli?
fertility f-plasmids
what type of plasmids contain genes that code for bacteriocins (proteins that can kill other bacteria)?
col plasmids
*some are also toxic to host cells (genotoxins)
what type of plasmids encode virulence factors and can convert a bacterium into a pathogen?
virulence plasmids
what type of plasmids contain genes that provide resistance against antibiotics or poisons, and were historically known as R-factors before the nature of plasmids was understood?
resistance (R) plasmids
some plasmids can only be transferred by tagging along with other plasmids that contain which genes?
tra genes
what are transposable elements?
DNA elements that move from one place in bacterial DNA to another
transposable elements can transfer genes to a new location or disrupt genes when they ___
insert
transposable elements can carry ___ and ___ resistance genes
virulence and antibiotic
what happens in replicative transposition?
the transposable elements leave a copy behind
in transposable elements, ___ will move the transposon to a new site
direct transposition
what are pathogenicity islands (PAIs)?
many virulence genes in compact, distinct genomic islands
pathogenicity islands are acquired by ___
horizontal gene transfer
pathogenicity islands have different ___ content than the rest of the bacterial chromosome
G-C%
natural populations of many pathogens have a clonal structure. in some cases, single clones are responsible for ___
geographically widespread disease
