Initially, geneticists assumed that the junction would adopt a parallel rather than antiparallel conformation, because that would place the homologous duplexes in closer alignment to each other. Chemical analysis in the 1980s showed that the junction actually preferred the antiparallel conformation, a finding that was considered controversial, and Robin Holliday himself initially doubted the findings. The antiparallel structure later became widely accepted due to X-ray crystallography data on "in vitro" molecules, although as of 2004 the implications for the "in vivo" structure remained unclear, especially the structure of the junctions is often altered by proteins bound to it.