Bacterial Genetics Flashcards
What does this:
allows coordinated response of multiple genes to environmental changes
control of gene expression
What does the operan do?
it can activate or turn off expression of a gene or group of genes
How is the operan kept under control?
by the promoter or repressor DNA sequence
What does control of gene expression in pathogens alow for?
quorum sensing
pathogenicity islands
toxin production
hemolysin production
What is responsible for the degredation of lactose?
lactose operon
What is a good example of transcription initiation?
lactose operon
What is the most common form of control of gene expression in bacteria?
negative regulation
Lactose degredation involves how many enzymes?
three
On a chromosome, where are structural genes located?
next to one another
What are the three control genes in the lactose operon?
promoter
operon
regulatory gene
In the lactose operon, what does the promoter do?
it is the region of DNA where RNA polymerase initiates transcription
In the lactose operon, what does the operon do?
acts as traffic light for transcription of structural genes
In the lactose operon, what does the regulatory gene do?
codes for repressor protein
In the absence of lactose, what does the lac operon do?
operon gets repressed by binding of repressor protein to operator sequence
What happens when lactose is present?
lactose binds to repressor protein and reverses the repression
The operon is regulated by the product of the (blank)
regulatory gene
What are the mutations you get with a single base change?
silent mutation
missense mutation
What is a missense mutation?
a change in amino acid
What is a silent mutation?
no change in encoded amino acid
What are the mutations involved with changing numerous bases?
frameshift
null mutation
What 2 ways can you get a null mutation?
- extensive insertion, deletion or gross rearrangement
- by recombination or genetic engineering
What happens when you get a null mutation?
you destroy gene function
Is mutation an efficient means for development of antibiotic resistance?
no!!! (because such a small mutation would never be able to incorporate enough DNA to cause resistance)
What are the three ways you can get genetic exchange?
transformation
conjugation
tranduction
What is transformation?
the uptake of naked DNA
What is conjugation?
How does it work?
one-way direct cell-to-cell transfer of DNA through the sex pilus
What is the common way for transfer of antibiotic resistance between species?
conjugation
What is transduction?
transfer of genetic material via bacterial viruses
Can you get transduction between very different species?
not really… its usually between the same or closely related species
What is transformation?
uptake of naked DNA
What does transformation require?
a competent cell
What bacterial species can undergo transformation?
streptococcus pneumoniae
Neisseria gonorrhea
Can you artificially cause transformation?
yes via electroporation or inducing changes in membrane permeability
How is the naked DNA integrated into a chromosome in transformation?
via homologous recombination
What is this:
one way transfer of DNA from a donor (male) cell to a recipient (female) through a sex pilus
conjugation
What does conjugation require?
direct cell contact
F factor
What is an F factor?
a special fertility factor found in the donor cell
How is the F factor stably maintained?
within a plasmid
WHat is a plasmid?
small genetic elements that can replicated indepenently of the bacterial chromosome
What is an episome?
a plasmid that can integrate into the host chromosome
How do you transfer the F factor in conjugation?
with the F plasmid and F pilus
What does the F plasmid have within it?
all the genes necessary for its own transfer
ability to make sex pilus
ability to initiate DNA synthesis at the transfer origin of the plasmid
When you the bacteria has an F plasmid does this make it male or female?
male
During mating for conjugation what happens to the F plasmid?
it transfers its self make the recipient F+
What does the F pilus do?
binds to recipient F- cell and brings pair in close proximity
What is the F pilus made up of?
repeating units of a single protein called F pilin
How do you make high frequency recombinant cell?
You get recombination b/w F factor and chromosome at a specific site and then insertion of F factor.
Explain how to the transfer of chromosomal genes via F factor works
You have an Hfr cell and a F- cell. There is site specific cleavage at the replication origin (oriT),
genes adjacent to F factor go into chromosome of recipient bacteria then F factor goes last.
how can you manipulate bacteria into doing Hfr?
reciprocal recombination
What was the first way to map genes?
via diruption of transfer at various time points in Hfr
What can plasmids do?
give bacteria resistance, encode for toxins and attachment proteins, aid in metabolic pathways
What can give bacteria resistance to many antibacterial compounds including heavy metas, mercurials and toxic anions?
plasmids
What all can plasmids give bacteria resistance to?
antibiotics
metals
radiation
bacteriophages
What can plasmids create?
bacteriocins (compounds toxic for other bacteria) virulece factors (toxins, attachment proteins)
What can plasmids participate in?
various metabolic pathways
What do transposons do?
transfer DNA within a cell
What are the 2 ways transposons can transfer DNA within a cell?
from one position to another in genome
between diferent molecules of DNA, e.g plasmid to genome
What are simple transposons?
insertion sequence and transpoase gene
What are insertion sequences?
inverted repeats that provide ends needed for recognition by transpoase
(blank) is an enzyme that binds to the ends of a transposon and catalyzes the movement of the transposon to another part of the genome by a cut and paste mechanism or a replicative transposition mechanism.
Transposase
Unlike homologous recombination, transposase does not require regions of (blank) for insertion
extensive homology
What are complex transposons?
they include insertion sequences and carry additoinal genes (ie antibiotic resistance or toxin production)
What are conjugal resistance plasmids?
They carry RTF (resistance transfer factor) that can carry drug resistant transposons :)
Are conjugal resistance plasmids dangerous?
super dangerous!
What is the abreviation for drug resistance tranposons?
r-determinant
What does RTF (resistance transfer factor) do?
encodes genes needed for conjugal transfer
What is the mechanism for multiple drug resistance (transposon component -r factor), mechanism for transfer to new bacteria (RTF) and if the plasmid carries multiple resistance genes, treatment with one antibiotic promotes resistance to multiple antibiotics?
conjugal resistance plasmid
What is a bacteriophage?
it is a virus that infects bacteria
What is transduction?
genetic transfer mediation by bacterial viruses (bacteriophages)
How does transduction work?
During process of viral replication, portions of the bacterial chromosome may be packaged into the bacteriophage particle.
What is generalized transduction?
Viral particles contain ONLY bacterial DNA
It is random due to accidental packaging of host DNA
(i.e virus destorys bacterial cell and accidently packages itsef with bacterial DNA and then infects a new bacteria and inadvertently gives that new bacteria the old bacterias skill set)
What is specialized transduction?
Phage is in host cell and steals some of its genes and then leaves the cell and incorporates itself into the genome of a new cell so that the new cell (bacteria) now has the properties of the first cell.
(this has both viral and bacterial DNA)
T or F
Many bacterial virulence genes are encoded by temperate bacteriophage, e.g., diphtheria toxin
T
So what is the lytic cycle?
When a phage enters a host cell and replicates to the point of killing the host cell
What is the lysogenic cycle?
phage intergrates its DNA into bacterial chromosome and allows bacteria to reproduce normally thus replicating the viral DNA (on occasion the virus can excise from the bacterial chromosome and initiate a lytic cycle)
Generalized transduction is one way for transfer of genetic information from one bacterium to another.Which of the following is a property of generalized transduction?
Transducing phage particles contain only bacterial DNA
Transformation is the transfer of DNA from a donor to a recipient cell
As naked DNA in solution
What is the most common means by which bacterial cells control gene expression?
Transcription control, most often via repressor proteins that block transcription
