Happy Hollidays: 40th anniversary of the Holliday junction.

In 1964, the geneticist Robin Holliday proposed a mechanism of DNA-strand exchange that attempted to explain gene-conversion events that occur during meiosis in fungi. His proposal marked the birthday of the now famous cross-stranded DNA structure, or Holliday junction. To understand the importance of the Holliday model we must look back in the history of science beyond the last 40 years, to a time when theories of heredity were being proposed by Gregor Johann Mendel.