Mutation and Plasmids Flashcards
Can switch back and forth between keto and enol structure when incorporated into DNA
5-bromouricil (BU)
Three-ring structure with the same shape and size as a base pair
Ethidium bromide
Causes double-strand breaks in the DNA backbone
Highly Ionizing Radiation
Causes oxidative deamination of amino groups to keto groups which changes the base pairing properties of the modified base
Nitrous acid
Adds an alkyl group to N-7 on purine ring resulting in depurination
(EMS) Ethyl Methane Sulfonate
Activates the SOS repair system
UV light
Can cause cyclobutane pyrimidine dimers and (6-4) photoproducts
UV light
Chemical mutagen that reacts with cytosine and converts it to a form that pairs with “A”
Hydroxylamine
RecA protein plays a role in this repair mechanism
SOS repair
LexA protein prevents transcription of this repair systems genes until induction occurs
SOS repair
Invokes production of error-prone DNA polymerases during replication
SOS repair
Determines which strand to repair by the degree of base methylation on each strand
Mismatch repair
Amino acid substitution that does not change the structure of the protein
Neutral mutation
Change in a single DNA base
Point mutation
Mutation in a gene that results in mutations occuring in other genes on the chromosome
mutator gene
Mutant tRNA that can recognize 2 different codons
Missense suppressor
Mutation that alters the reading frame of mRNA resulting in abnormal AA sequence
Frame shift mutation
Physical or chemical agent that causes mutation
mutagen
Change in a base sequence that prematurely terminates the polypeptide during translation
nonsense mutation
tRNA with the wrong amino acid attached to it
mischarged tRNA
Activates an alternative metabolic pathway that eliminates the original mutation
Bypass supressor
Alteration of DNA structure that can be caused by some antibiotics
Crosslinking
Steric requirements at third position in the codon are less stringent for translation
Wobble Hypothesis
A mutant that exhibits reduced enzymatic activity
Leaky Mutation
Can perform error-prone synthesis across lesions on ds-DNA
DNA polymerase V
How would you isolate a spontaneous E. coli mutant that cannot synthesize its own valine? Describe the plating method you would need to utilize.
Plate E. coli on a valine-containing plate and replicate the plate onto a non-valine plate using a stamp. By comparing the two plates, you will be able to tell that the colonies that do not form on the non-valine plate correlate to the Val- colonies that did grow on the valine-containing plate.
Nonconjugative mobilized plasmid transferred by conjugative plasmid
Donation
Plasmid that only has genes for effective contact
Conjugative plasmid
High copy number plasmid
Relaxed plasmid
Plasmid that contains antibiotic resistant genes
R plasmid
Identification gene on transferred plasmid to indicate transconjugants (phenotypic expression)
Selected Marker
Formation of a functional plasmid in a recipient cell
Repliconation
Plasmids transferred and maintained in a large number of bacterial species
Broad host range plasmid
Bacterial plasmid that can integrate into plant cell DNA
Ti plasmid
Plasmid containing genes for proteins which kill closely relates strains
Col plasmid
Protein that controls the plasmid copy number in a bacterial cell
Rep protein
Closely related plasmids cannot be maintained in the same cell
plasmid incompatibility
List 5 basic features of plasmids
- Extrachromosomal circular DNA molecules
- Found in most bacteria, some eukaryotic cells (yeast)
- Have own genes for regulating time of synthesis
- Dependent on host metabolism for replication
- Contain essential genes for certain situations (antibiotic resistance)
What are the 4 basic steps of the transfer process for bacterial conjugation?
- Effective contact (donor-recipient pair)
- Mobilization (prepare DNA for transfer)
- DNA transfer
- Repliconation - formation of a functional plasmid in recipient cell
In the conjugation experiment, what is the selected marker gene and what is the counter-selected marker gene for the mating? What is the purpose of the counter-selected marker gene?
Selected marker gene - the Lac+ plasmid that was given to the recipient by the donor through conjugation.Counter-selected marker gene - The streptomycin resistant (Str^r) gene carried by the recipient. This is visible after plating both on antibiotic and Lac+ agar as cellular proliferation of recipient cells only.
