In the previous chapters in Part III, I considered a variety of ways by which changes in gene dosage can effect alterations in metabolism, regulation, cellular structure, and pattern formation. In each instance, the attempt was made to demonstrate how a 50% increase or decrease in gene product could produce a characteristic effect based on the function of the product in question. The relationship between the change in gene number and the phenotypic change or changes that ultimately resulted was regarded as a specific one. In some cases the relationship might be a direct one, but in others the actual pathway between genetic imbalance and phenotype might involve several steps and be difficult to trace.

However, not everyone shares this belief in the specificity of aneuploid effects. It is appropriate, therefore, to consider the arguments made for the existence of nonspecific effects, effects which are not wholly a product of the particular loci that are unbalanced but derive from a more general perturbation in genetic structure or balance.

Regulatory disturbance

Mention has already been made of the possible major role of regulatory disturbances, as proposed, for example, by Krone and Wolf (1972) and by Vogel (1973), to explain the effects of aneuploidy. These effects would not need to be nonspecific if we were dealing with the imbalance of specific regulatory loci, no matter how many structural loci they interacted with.