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homologous recombination 1 - Coggle Diagram
homologous recombination 1
Homologous recombination
General mechanism
ds break in homo chromo
A
strand resection
(bit of 5' digestion on both pieces)
homo chromo
B
is opened at equivalent bit to break
homo chromo
A
3' sticky search for comp bit on homo chromo
B
when bound, DNA pol fills in some nucleos
structures called
Holliday junctions
form, where DNA for two homos cross
VISUAL AID IN ONENOTE
Holliday's migrate past nick
2 more items...
this forms a structure called a...
D loop
BOTH PIECES OF BROKEN dna DO THIS
STEP 9 (
in general mechanism
)
resolution of Holliday junctions
where the endonukes cut is important for the resulting DNA
NON-CROSSOVER
endonukes cut at same position either side of OG break
both at
Holliday junction
... or both at
outer most strand
MORE CLEAR FROM DIAGRAM
results in the bits of the strand before and after the break originating from same chromo
bit of the homo chromo in the middle
CROSSOVER
endonukes cut at
different
bits either side of OG break
e.g. 1 at
Holliday junction
... 1 at
outermost strand
results in the DNA having parts from each homo chromo either side of the break
think of crossing over in meiosis, its the exchange of material between homo chromos so it makes sense
when this process occurs matters
occurs in S and G2 in most cells
this is when chromosomes are sister tids, and so HR occurs between chromos that are BASICALLY identical
produces near perfect reversal from break
in germline cells, occurs during division process (meiosis)
HR occurs between maternal and paternal homo chromos (slightly less identical)
CROSSING OVER
HR in
prokaryotes
how can it work when only one circle DNA there?
while replicating, there is a period where there will be identical DNA, because its being
replicated
cool lab genetics manipulation of HR
when 3' sticky find comp bit on homo chromo (
step 4
)...
DNA pol fills in some nucleos... this part can be manipulated
if you insert some desired DNA of something in this comp bit, DNA pol will go ham and copy it