DNA Recombination Flashcards
Homologous recombination
Exchange between homologous DNA molecules during crossing over
Single strand break (Holliday) model Step 1
Homologous chromosomes align and single strand breaks occur in the same position on both DNA molecules
Single strand break (Holliday) model Step 2
A free strand of each broken strand migrates to the other DNA molecule
What happens to histones during replication
After replication, it is a mixture of old and new histones.
Replisome complex is also used as a
recombinosome complex - same proteins involved in both processes
Single strand break (Holliday) model Step 3
Each invading strand joins to the broken end of the other DNA molecule, creating a Holliday junction, and begins to displace the original complementary strand
Single strand break (Holliday) model Step 4
Branch migration takes place as the two nucleotide strands exchange positions, creating the two duplex molecules
Single strand break (Holliday) model Step 5
The ends of the two interconnected duplexes pull away from one another
Double strand break model Step 1
Two double stranded DNA molecules from homologous chromsomes align
Double strand break model Step 2
A double strand break occurs in one of the molecules
Double strand break model Step 3
Nucleotides are enzymatically removed, producing single-stranded DNA on each side
Double strand break model Step 4
A free 3’ end invades and displaces a strand of the unbroken DNA molecule.
Double strand break model Step 5
The 3’ end then elongates, further displacing the original strand.
Double strand break model Step 6
The displaced strand forms a loop that base pairs with the broken DNA molecule.
Double strand break model Step 7
DNA synthesis is initiated at the 3’ end of the bottom strand, the displaced loop being used as a template.
