Complementation Analysis: How Many Genes are Involved?

The laboratory test used by geneticists to determine whether two independently isolated mutations are located within the same or different genes is the complementation test. The methods of complementation analysis are discussed from a theoretical and operational perspective. Phenomena such as intragenic complementation or nonallelic noncomplementation occasionally complicate the analysis of the results of a complementation test. The interpretation of these phenomena and their significance with regard to the specific gene functions under study is discussed.