Enzymic de-adaptation: the stability of an acquired character on withdrawal of the external inducing stimulus.

Abstract

In most cases of enzymic induction (‘adaptation’) the specifically increased rate of enzyme production evoked by the presence of the inducer in the external environment returns to normal immediately the inducer is removed. However, the situation is not always so clear-cut. The changes in the cell underlying the phenomenon of enzyme induction have long been known to be—from a genetical standpoint—transitory. But the mechanism of enzymic reversion (‘de-adaptation’) has not yet been the subject of much systematic study. Most cell characters presumably have an underlying enzymic basis, and in most cases enzyme induction, even if under some sort of nuclear genetic control which determines its scope, appears to be almost certainly a cytoplasmic function. It therefore seems likely that a study of the specific gain and loss of enzymic function that occurs during enzymic adaptation or de-adaptation will prove to have some bearing on the problems of growth, variation and differentiation under conditions where the genetic background may be supposed to remain constant.