The double strand break model of meiotic recombination allows for unequal amounts of heteroduplex DNA either side of the initial site of recombination, explaining some results that the Meselson-Radding model of recombination does not.
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Firstly, a double strand break is made in one chromosome (hence the name)
aaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
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A 5' to 3' nuclease digests back along each strand of the duplex until it hits a chi site.
aaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
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RecA mediated invasion of chromosome 2 by one of the strands of chromosome 1 occurs.
aaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaa bbbb aaaaaaaaaaaaaaaaaaa
\ / \
X \
/ \ \
bbbbbb aaaa bbbbbbbbbbbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
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Strand A is extended with new DNA, which is represented by c (but note that c is identical to b - this is just to show the new DNA being produced). This displaces b, which continues to transfer over to the other chromosome.
aaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaa bbbbbbbbbbbbb aaaaaaaaaaaaaaaaaaa
\ / \
X \
/ \ \
bbbbbb ccccccccccccc bbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
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New DNA is synthesised to fill the gap on chromosome 1 (represented by d, but identical to b)
aaaaaadddddddaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaa bbbbbbbbbbbbb aaaaaaaaaaaaaaaaa
\ / \ /
X X
/ \ / \
bbbbbb ccccccccccccc bbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
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Due to the two junctions, there are too many possible outcomes to describe trivially. When comparing to other types of meiotic recombination, note the differing amounts of heteroduplex DNA on the two chromosomes.