The eye-pigmentary system ofdrosophila - IV. the pigments of the vermilion group oe mutants
The large number of eye-colour mutants ofDrosophila melanogaster is classified into several groups: vermilion, light, dark, ruby, red and variegated. The first group studied histologically and photometrically was the vermilion group, with the mutants scarlet (st), cinnabar (cn), vermilion(v), cardinal(cd) and karmoisin(kar).
Histologically the eyes of these mutants are very similar excepting that inst largersized granules (or aggregates) occur amongst the normal granules in the secondary pigment cells, and incd a smaller number of such granules appear in the distal parts of these cells.
The validity of the method of differential double extraction of the red and brown pigments is examined.
Evidence, based on the spectrophotometric curves of the extracts, is advanced for the affinities of the red and brown pigments, a common step in their chromophore formation being postulated during the stage of development of a precursor, or constituent, for combination with their specific chromogens.
An analysis of the light-absorption curves of pupal and imaginal eye extracts gives some indication of the course of development of the red and brown chromophores.
The five mutants produce mainly red pigment, although in the case ofcd a small amount of brown pigment is also produced and inkar about twice this amount. In regard to the red pigment content in these mutants no great difference was found as compared with the wild-type, excepting in the case ofcd which proved to possess a significantly greater amount.
To the known functions of the normal alleles ofv andcn may now be added some assumptions on the probable roles of the normal alleles ofst, kar andcd, these genes probably conditioning stages in the preparation of the substrate provided by the normal allele of white for combination with the brown chromogen, to result in the production of the brown chromophore.
Volume 100, 2021
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