Abstract
Recent work on allelism and pseudoallelism, especially with microorganisms, is discussed. It is concluded that the functional gene may be divisible into smaller mutable and recombinable components. The position effect observed with pseudoalleles can be caused, therefore, by mutations with the smaller genetic sub-units of the functional gene. Although the hypothesis of pseudoallelism between genes with different functions is not incompatible with the notion that functional units are subdivisible, no critical evidence is as yet at hand compelling this interpretation of the pseudoallelic position effect.
