L36 Flashcards
Are bacteria haploid or diploid?
Haploid
X nucleus
X introns
What is the structure of the bacterial ribosome?
30S (w/ 16 rRNA)
50S
What are the 3 major bacterial genetic elements?
- Chromosome
- Plasmid = independently replicating
- Transposon = integrates into plasmid or chromosome to replicate
What is the structure of transposons?
Start & end with inverted repeats
- allow for base pairing with the DNA it will integrate in with
tnpA = transposase gene
Ab resistant genes
What are insertion sequences?
Transposon - recongizable genetic patterns (i.e. no Ab resistance)
What is the action of transposons/insertion sequences?
Can inactivate target genes & cause genetic rearrangements
What is a bacteriophage?
Virus that infects bacteria
Can lyse & kill cells (lytic)
OR
Incorporate into bacterial DNA, replicate, then lyse cell (lysogenic)
What are pathogenicity islands?
DNA w/ virulence genes
@ “house keeping” part of the DNA
Nonpathogenic strains of bacteria can acquire PIs & gain properties responsible for disease
What are the 3 mechanisms of genetic exchange?
Transformation
Conjugation
Transduction
What is transformation?
Naked DNA from 1 cell taken up by another cell w/o participation of other bacteria/virus
What is conjugation?
Genetic transfer via cell-cell contact
Sexual mating
How does E.Coli accomplish conjugation?
F factor = fertility factor
- Encodes the sex pilus
Is an episome = capable of integrating into chromosome
What is high frequency recombination?
Once F factor is in the chromosome, can lead adjacent chromosomal regions out of donor cell and into recipient via single stand & replication
What is transduction?
Transfer of DNA between bacteria via VIRUSES
What are the 2 types of transduction?
Specialized = phage always integrates into specific site in host chromosome Generalized = gene transfer in random manner
What is a regulon?
Multiple DNA operons linked together in a global regulatory network
Doesn’t have to be a physical link
Where is the most important site of bacterial regulation of DNA replication?
Initiation of transcription
What is a 2 component regulatory system?
Sensory = sees changes in environment, transmits signal to regulator Regulator = binds DNA and changes transcription via phosphorylation
What is quorum sensing?
How bacteria secrete low molecular weight compounds to signal other bacteria to turn on specific gene expression
Low [ ]s - no effect b/c diluted
High [ ]s - regulation of genetics in other bacterial
How does an autoinducer work?
Binds & actviates transcriptional regulator to turn on specific genes
Due to quorum sensing
What are simple ways that a bacteria can change the way its DNA is arranged to alter pathogen properties?
Duplication
Gene amplification
Deletion
What is phase variation?
Reversible switch on/off of expression phases to change a pathogen’s properties
Genetic mechanism that can lead to antigenic variation
What is antigenic variation?
Expression of antigenically distinct but functionally conserved moieties within a population
To change a pathogen’s properties
“Gene conversion”
Give an example/explain phase variation by gene inversion.
Salmonella
@ transcription
Alternate between H1 & H2 antigens
Controlled by recombinase that acts on inverted repeats to change orientation of genetic fragment
