Test of Cairns-Smith's 'crystals-as-genes' hypothesis.

One aspect of the multifaceted proposal by A. G. Cairns-Smith, that imperfect crystals have the capacity to act as primitive genes by transferring the disposition of their imperfections from one crystal to another, is investigated. Rather than examining clay minerals, the most likely crystalline genes in the theories of Cairns-Smith, an experiment was designed in a model crystalline system unrelated to the composition of the prebiotic earth but suited to a well-defined test. Plates of potassium hydrogen phthalate riddled with dislocations were studied in order to ascertain whether, according to Cairns-Smith, parallel screw dislocations could serve as an information store with cores akin to punches in an old computer card. Evidence of screw dislocations was obtained from their associated growth hillocks through differential interference contrast microscopy, atomic force microscopy, and luminescence labeling of hillocks in conjunction with confocal laser scanning microscopy. The dispositions of growth active hillocks were quantified by fractal analysis. 'Mother' crystals were cleaved and inheritance was evaluated by the corresponding patterns of luminescence developed in their 'daughters' after continued growth in the presence of fluorophores. Luminescence microscopy proves to be a versatile tool for studying the dynamics of growth active hillocks. In the aggregate, this work speaks to the need for molecular mechanisms of dislocation nucleation.