Structural Biochemistry/Holliday Junction

Holliday Junction

A Holliday Junction is the combination of four moving DNA strands that bridge together to form four double-helical arms. This model was proposed by Robin Holliday in 1964 to explain the transfer of genetic information in yeast, now known as homologous recombination. (1)

2-D View of the Holliday Junction

However, this structure is unstable because they contain homologous sequence symmetry, which allows itself to isomerize. These junctions can slide up and down the DNA since they are between homologous sequences. When there are a few single strands with the same length, the free ends of each strand can match up to another DNA helix with free ends. The strands are now crossed over, which creates the Holliday junction. (2)