M2 U3 Bacterial Genetics Flashcards
(15 cards)
What is lysogeny ?
Stable pieces of phage DNA (called prophage) may be inserted into the bacterial chromosome
What is lysogenic conversion ?
Lysogeny takes place and replicates with bacterial DNA, following infection with a temperate phage (a repressed virus)
What are referred to as jumping genes ? and why ?
Transposons, can move themselves or copy from one molecule of DNA to another
What is transposition ?
The transfer of transposons between one plasmid to another, or between plasmid and chromosome within a bacterial cell
What is genetic exchange ?
The unilateral transfer of genetic information from a donor cell to a recipient cell
What is conjugation in genetic exchange ?
The gene transfer from one bacterial cell to another involving direct cell-to-cell contact
Why is the F+ x F- conjugation have no genetic recombination while the Hfr x F- conjugation has recombination ?
F+ x F- conjugation only transfers the F factor and becomes a free element in the cytoplasm, where it is replicated independently of the chromosome
In Hfr x F- the recipient gets some donor chromosomal genes that can recombine with its own chromosome, where it becomes a recombinant F- cell
What is transformation in genetic exchange ?
The uptake of free (or naked) extracellular DNA in the environment by a competent cell and subsequent integration into its chromosome by a competent
What is artificial (or forced) transformation in genetic exchange ?
A procedure where in the DNA is extracted, and treatment of cells with high salt and temperature shock to render the cell membrane more permeable to DNA and make them readily take up DNA
What is transduction in genetic exchange ?
Transfer of DNA between bacteria by means of a phage
What is a virulent phage ?
This infects bacterial cells, replicates, and kills the host bacteria, usually by lysing - lytic cycle
What is a temperate phage ?
These integrate their DNA into bacterial chromosome where it stably stays as a prophage without lysing the host bacteria - lysogeny
Often have repressor genes to prevent phage replication
In the absence of functional repressor protein, they also may replicate lytically
Where can transducing particles be found and what are they ?
They can be found in general transduction and this is when bacterial DNA are packaged in a phage capsid by mistake
What is spontaneous mutation ?
It is a random, undirected alteration of the DNA base sequence that arise as a consequence of mistakes in DNA replication
What is induced mutation ?
These are caused by exposure to external influences or agents that result in the DNA to breakdown
