Mechanisms of Genetic Exchange in Bacteria (selfstudy)-Howe Flashcards
What is a cistron?
a segment f DNA encoding a polypeptide
What is an operon?
the unit of transcription. Typically consists of a promoter region, operator region, component cistrons, and terminator.
What is a repressor?
protein that binds to regulator blocks of DNA and supresses gene expression
What is a regulon?
a group of genes subject to the control of a common regulator.
What are biased random walks?
alterations in the frequency of productive motion called a run and tumbling in place. The run is actual movement in a single direction. The tumble is the cell rotating, but not going anywhere. When something in the direction of its movement repels it, it randomly tumbles in a direction. When it finally is turned the right way, it runs.
What is the removal of a single nucleotide and it’s complement in the opposite strand called? What is it called when multiple nucleotides are removed?
microdeletion. These cause frameshifts
deletion if multiple
What is an inversion?
the change in direction of a segment of DNA by splicing each strand of the segment into the complementary strand.
What is it called when a genetic mutation causes one AA to change to a new one?
missense mutation
What is it called when a mutation causes an AA specifying gene to now produce nothing? (stop codon)
Nonsense mutation
What is a polar mutation?
mutation that blocks transcription of all genes downstream of it. A nonsense mutation is an example.
When does recombination occur in eukaryotes? prokaryotes?
crossing over during meiosis for eukaryotes
Prokaryotic cells can become recombinant anytime there is a source of recombinant DNA or when strands break in the bacterial chromosome. (can come from exogenous sources or internally)
What enzyme is necessary for homologous recombination? What else is required?
RecA (recombinantion) controls the breakage and reunion process.
The donor DNA must possess reasonably large regions of nucleotide sequence that are similar to the host chromosome to allow extensive base-pairing.
What is site-specific recombination?
pretty much what it sounds like. A specific strand of DNA is sought out and targeted, broken, then recombinant DNA is inserted.
Commonly used by viruses.
What is antigenic variation?
ability to use genetic recombination to shut certain functions on or off. This is useful because some bacteria can change their cell surface appearance (flagella, pili, etc) and avoid mounting immune responses.
What is transposition?
genetic elements that are capable of mediating their own transfer from one chromosome to another.
What is transformation, in terms of bacterial genetic exchange?
it is the sharing of genetic info between related species by release of DNA into environment by lysis of some cells
What is transduction?
DNA introduced to cell by bacteriophage that has infected it.
What is conjugation?
actual contact between donor and recipient cell and plasmid transfer through (sex pili in gram-negative) and (conjugation bridges/clumping in gram-positive)
What is the ability to take up DNA from the environment called?
competence
What is lysogeny?
the condition of having a latent virus that can pass back and forth between latent and virulent stages which can cause lysis
What is a plasmid?
autonomous extrachromosomal elements composed of circular double-stranded DNA. Many have the capacity to bring about their own transfer to other cells (conjugation).
What is it called when a non-conjugative plasmid is transferred because a conjugative plasmid has tried to transfer itself?
plasmid mobilization
What type of recombination do most R-plasmids use (resistance plasmids)?
transposon.
Rank these in order of most DNA transfered to least: transformation, conjugation, transduction.
Conjugation (20-25% of the chromosome)–>transformation (5-10%) –> transduction (1-2%)
Which type of genetic transfer requires a virus?
generalized transduction. (also specialized)
Do transposable elements require DNA sequence homology in the target DNA?
no. they are capable of moving most anywhere
What are tra genes?
??
What is an insertion sequence?
a sequence of DNA that is transposable. Bare minimum for transposition, does not carry phenotypic information.
What are Type 1 composite transposons?
larger DNA elements with long repeats at ends. often carry antibiotic resistance code in the center.
What are Tn3-like transposons?
larger transposons similar to type 1, but with short inverted repeats at the ends. They can NOT transpose independently.
