Imprinting a determined state into the chromatin of Drosophila.

The Polycomb gene of Drosophila melanogaster is a member of a class of genes involved in the clonal transmission of the repressed state of bomeotic regulatory genes through development. Genetic evidence, and the finding of a molecular similarity between the Polycomb protein and a heterochromatin-associated protein of Drosophila, suggest that this mechanism of repression might be imprinted in the structure of the chromatin, rather than being sustained through the action of diffusible regulatory factors.