that = accident?

Context:

This structure is not merely an accident of chemical attractions within and among the chromosomes -- although that is certainly a part of the larger whole -- but an arrangement guided by other molecules in the cell to create a mega-structure that dictates genetic function, Noma says. He envisions a scenario where accessory molecules, such as gene-promoting transcription factors, bind to DNA and contribute to the ultimate structure of the genome as the chromosomes fold together.