Chromosomal and extrachromosomal transmission of cellular melanization in the Freckled phenotype in Drosophila melanogaster

Abstract

Freckled (Frd) is a dominant mutant of D. melanogaster, lethal in double dose, which manifests itself by melanization in the adult stage, while nothing can be noticed in the larva and/or in the pupa. Its localization has been determined at nearly 102 of the second chromosome.Among the offspring from backcrosses involving Frd, some individuals that do not carry the Frd gene exhibit a weak Frd manifestation in the adult stage, or a stronger one, mostly lethal, in the larval or pupal stage. Weak Frd, indicated as [Frd], is transmitted indefinitely without any recognizable linkage with the chromosomes, although its frequency is influenced by the 1st and, probably, by the 3rd chromosome. No matroclinous transmission has been found. It is concluded that [Frd] is probably controlled by an extrachromosomal entity, not located in the cytoplasm. The possible relationships between Frd and [Frd] are discussed.