Genelogic dilution experiment: Hook curves for different dilution steps (upper panel), the fraction of absent probes (middle panel) and concentration measures (S/N-ratio and specific binding strength, lower panel) as a function of the amount of added RNA. The dilution of the hybridization solution shifts the increasing part of the hooks to the left and increases its width. The width is inversely related to the non-specific binding strength, ~-log XN, which consequently decreases upon dilution. The horizontal dotted lines in the upper part indicate the levels of different S/N-ratio (R); the dashed parabola-like curves are fits of the Langmuir-hybridization model. The hook method provides a virtually constant fraction of absent probes which corresponds to the essentially invariant S/N-ratio of the probes upon changing dilution. Contrarily, MAS5 provides an increasing fraction of absent probes (see middle panel). The lower part compares the S/N-ratio of selected probes which remain virtually constant upon dilution with the binding strength which progressively decreases (compare lines and solid symbols in the lower part; the diagonal lines refer to the right coordinate axis).