The yellow condition in Drosophila melanogaster. A biological structuralist approach to the study of phenocopies.

A phenocopy, as defined by Goldschmidt, is an environmentally induced form which resembles a genetic mutant. They have a site of induction at a number of developmental levels and are not only produced by interfering with gene gene expression. Phenocopies and the corresponding genetic mutant, are also not necessarily generated through equivalent developmental pathways. The yellow phenocopy of Drosophila melanogaster, where both cuticle colour and mating behaviour resembles that of the yellow mutant, serves to illustrate the above points. It is suggested that if the term phenocopy is to be used the term should correspond to the generative processes and hence transformations which mutant and phenocopy share, rather than purely on phenotype. Finally, phenocopies are discussed in relation to structuralist biology, showing how they are instructive in describing generative processes, sensitive periods in development and differing modes of inheritance in such a research programme.