Recombination:nicking of DNA, single stranded overhang attacks the duplex, strand displacement,
further synthesis of DNA, intermediatejunction
E. coli RecBCD Pathway of Homologous Recombination I
SometimesRecABCD -recA helps in homologysearch
Repair is the initial condition that drove evolution
BCD - encodes for different subunits
Under conditions of high magnesium, the activity is higher
Acts as endonuclease,and degrades and unwinds DNA, until it reaches a Chi site (a consensus).
Chi sites serve as initiator for replication.
Overhang gets coded by recA protein.
30 bp is not enough, if over this, the D-loop will form (displacement-formation),after which recA is
ATP is needed to unload (no ATP no recombination!)
HOLLIDAY junction - the polynucleotideswitch between duplex
- They are heteroduplex which contain potential mismatches(contain both blue and red from
- Holliday junction migration - A diffusion process, it is neutral, slow process, less enzymes are - Holliday junction migration - A diffusion process, it is neutral, slow process, less enzymes are
G and H resolutions are two possible resolutions - equally likely to happen
RuvC - enzyme that drives the resolution
H is the parental resolution (heteroduplexes: non-crossover recombinants)- blue with blue, red with
G is another resolution (crossoverrecombinants) - red with blue
Binding of RecA to single-stranded DNA
Single stranded areas are much thicker than double stranded areas - protein are bound to DNA (they
At the right pic, same thing, the single stranded DNA are fat
The left pic is a nicer experiment than the right one because there's no control