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Holiday model of recombination

created by Fluffy The Cat

(thing) by Fluffy The Cat (1.8 y) (print)   ?   (I like it!) 1 C! Wed May 23 2001 at 23:55:01

The Holiday model was the first model to describe meiotic recombination. It is quite simple, but does not describe all observed results and so has been mostly discarded in favour of newer models. However, it does serve as a good introduction to recombination.
  1. The two chromosomes are next to each other 
    
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    (Note that each chromosome is a double helix)
  2. One strand from each chromosome is nicked and transfers to the other chromosome 
    
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaaaaaaaaaaaa   aaaaaaaaaaaaaaaaaaaaaaaaaaa
                \ /
                 X
                / \
bbbbbbbbbbbbbbbb   bbbbbbbbbbbbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
  3. The branch may migrate, creating a region of heteroduplex DNA 
    
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaaaaaaaaaaaabbbbbbbbbb   aaaaaaaaaaaaaaaaa
                          \ /
                           X
                          / \
bbbbbbbbbbbbbbbbaaaaaaaaaa   bbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

    (that is, there is now a section where part of each double helix is originally from the adjacent double helix)
  4. The Holiday junction is resolved in one of two ways. Both leave heteroduplex DNA, but only one is recombinant.

    (Type 1 - heteroduplex but non-recombinant) 

    
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 1
aaaaaaaaaaaaaaaabbbbbbbbbbaaaaaaaaaaaaaaaaaaa


bbbbbbbbbbbbbbbbaaaaaaaaaabbbbbbbbbbbbbbbbbbb
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

    (Type 2 - heteroduplex and recombinant) 

    
aaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbb
Chromosome 1
aaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbbbbbbbbb


bbbbbbbbbbbbbbbbaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Chromosome 2
bbbbbbbbbbbbbbbbbbbbbbbbbbbaaaaaaaaaaaaaaaaaa

printable version
chaos

sister chromatid meiotic recombination Double strand break model of recombination Meselson-Radding model of recombination
Holiday In Spain Patriot Day RecA recombination
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