The genetics and biochemistry of red fat cells in Drosophila melanogaster.

N the strain of Drosophila known as “red fat cells” conspicuous pigmented Icells are visible in the head and thorax of the flies (JONES and LEWIS 1957). Normally colorless fat cells acquire a pigment that is related to, or perhaps identical with, the brown ommochrome derived from tryptophan. This report concerns some properties of the red fat cells (RFC) strain, two of which have been briefly reported (GRELL 1958). The larvae, pupae and adults of the RFC strain contain much more of the amino acid, lysine, than wild-type animals. The RFC phenotype is the result of an interaction between two mutants, lysine ( lys) and red cells (rc) . Each of these mutant loci seems to have the tendency to produce pigmented fat cells in the absence of the other, but this tendency is expressed only under special conditions.