Flashcards in Site Specific Recombination and Transposition Deck (20)
What are the two ways by which discrete segments of DNA can move from one region of the genome to another?
1) Site-specific recombination 2) Transposition
Site Specific recombination structure.
a) CSSR conservative site-specific recombination (CATACA) recombination site. (b) Flanked by Cre binding sites that aid in recombination protein binding
bind to the cre binding site. cleave phosphodiester backbone of DNA. Act like topoisomerases (no ATP involved)
What is the only way that SSR will occur?
the region of strand exchange between the two DNA molecules must be in the same direction.
sites are in the same direction - leads to excision
sites in inverted oreintation
sites are not in the same direction - leads to inversion
Mechanism of site specific recombination
1. regions of strand exchange line up 2. recombinase does nucleophilic attack on phosphodiester backbone (tyrosine leads to 5'OH formation, while serine leads to 3'OH formation) 3) tyro-phosphate groups and OH groups on opposite strands attract. 4) other set of topoisomerases produce OH and tryophosphates which combine and repair to form two different strands.
SSR on the same DNA molecule
If rec sites are in opposed direction, inversion; if rec sites are in the same direction you get an insertion and deletion.
jumping genes, short sequences (transposons) can excise and reinsert at a different place in the genome.
reads one way L-R and the same way R-L on a different site on DNA
encodes transpoases; transposases recognize IRs, cut piece of DNA out of site, and move it to different site.
mobile genetic element
can move from one region to another
regions on target DNA that recognize ends of transposons ( terminal repeats). gaps mad when transposon and target DNA are fixed by DNA repair mechanism. The flanking DNA act as templates.
(DS breaks) 1) Cleavage of transposons 2) Free ends of transposons attack target DNA 3) Gaps filled (left) by DNA polymerase and ligase
1) Cleavage of transposons 2) Free ends of transposons attack target DNA 3) entire transposon replicated 4) Site specific recombination (with in the transposon) DNAP III mediated replication,
What type of recombination produces genetic diversity in adaptive immunity?
Site specific recombination during assembly of Ig genes.
Occurs in light chain
VJ recombination process
1) RSS sequence associated with V segment and J segment 2) Recombinase binds to RSS sequence on V and J. 3) Rag1/2 form 3'OH and the 3'OH does a nucleophilic attack on its own strand watson-crick strand. 4) The genetic information in the middle gets removed.