gene transfer Flashcards
(20 cards)
types of horizontal gene transfer
transformation, transduction, conjugation
what is transformation?
the uptake of naked DNA by competent cells
what is transduction?
the transfer of bacterial DNA by bacteriophage
what is conjugation?
transfer of DNA by direct physical contact
what occurs in natural transformation?
DNA from donor bacterium, random process, any portion of genome transferred
where does the naked DNA come from?
bacteria that lyse and release DNA
what is factor in competency of cell?
phase of growth
mechanism of transformation
competent cell binds DNA molecule, DNA cleaved into 5 - 15 kbps by endonuclease, one strand hydrolysed by exonuclease, other strand integrates by recombination
artificial transformation methods
heat shock with CaCl2 treatment or electroporation
differences in haemophillus transformation
only similar DNA uptake, no competence factor, specificity due to highly repeated sequence, ds DNA complexed with protein in vesicles,
who discovered conjugation?
Lederberg and Tatum
what does F factor stand for?
fertility factor
what is the F factor?
100kb long contains genes for pilus formation and gene transfer
what is Hfr
high frequency recombination
how does Fâ occur?
imprecise excision of integrated f plasmid from chromosome
what is Hfr used for?
to map the relative location of bacterial genes
what is the lytic cycle in transduction?
generalized - any random segment of DNA can be transferred
what is the lysogenic cycle in transduction?
specialized - only genes adjacent to the integrated virus are transferred
how does transduction work?
bacterial genes incorporated in phage capsid due to errors in virus life cycle, defective viruses are injected into another bacterium
generalized transduction mechanism
capsid assembles around donor DNA, defective bacteriophage released, DNA containing bacteriophage adsorbs onto recipient bacteria, delivers DNA
