Section 10 — Developmental Genetics 



effect becomes stronger as development progres- 

 ses. 



E-H and Su-H are both closely linked to and 

 on the same side of the locus black on chromo- 

 some II. It is therefore quite possible that these 

 different modifiers are mutants at one and the 

 same locus within the system controlling the 

 level of production at the Hairless locus; they 

 act as if they were "constitutive" {Su-H) and 

 "super-repressed" (E-H) mutants. 



10.18. On the Effects of rolled (rl) in Drosophila 

 melanogaster. S. T. Lakovaara (Helsinki, 

 Finland). 



In homozygous rolled flies (chromosome 2, 

 locus 55.1), the following features are observed: 

 wing edges rolled downward, venation of the 

 wings defective, eyes of subnormal size, darker 

 than normal and roughened. In hemizygotes, the 

 eyes are of half the normal size, dark red and 

 rough-surfaced. The wing venation is rudimen- 

 tary. In hemizygotes, Df (2) rl gives a stronger 

 effect than Df(2)MS-10. Heterozygotes are 

 normal. 



No change in hemizygotes is found after 

 addition of an extra Y or after loss of this 

 chromosome. However, factors decreasing wing 

 size increase the size of the eye in the combi- 

 nations tested ( W,Bd G , vg) . 



In both homo- and hemizygotes, the strongest 

 effects are found at 26°C, with a lessening at 

 temperatures above and below this value. In 

 histological sections, developmental defects are 

 observable in homo- and hemizygotes in the 

 ommatids as well as in the brain. Pigment is 

 apparently formed in normal amounts but its 

 location is changed. 



In conclusion it may be supposed that : In their 

 effect on the production of a substance important 

 for the development of both the eye and the 

 wing, the genotypes may be arranged in the 

 order rl/- < rl/rl < H/ + . The gene rl governs a 

 switch mechanism between the metabolic path- 

 ways leading to these two organs. The amount 

 of substance generated in the wing pathway can 

 be reduced by adding factors which have a wing- 

 reducing effect. As a "side effect", larger eyes 

 are obtained, owing to increased flow of the 

 common substance towards the eye pathway. 

 The temperature-dependent changes are due to 

 thermodynamic properties of the enzyme con- 

 trolled by rl. 



10.19. Transfer of Phosphorus Isotope from Parents 

 to Offspring in Drosophila melanogaster 



Meig. I. Csukas-Szatloczky (Budapest, 

 Hungary). 



The distribution of P 32 , incorporated by 

 Drosophila melanogaster, has been examined at 

 various stages of ontogeny, and also the con- 

 centration of phosphorus in the gametes of the 

 progeny has been studied. The method of 

 Schmidt and Tannhauser was employed for the 

 separation of fractions. The distribution of the 

 incorporated phosphorus was found to be 

 different in the examined fractions in different 

 phases of the ontogeny. 



The amount of phosphorus transferred by the 

 female sex cell was 50 times that transferred by 

 the male cell measured at the end of the stage 

 of third instar larva. 



A comparison of the distribution of phos- 

 phorus taken up from the nutrient medium with 

 that received by way of inheritance showed 

 sharp differences in the various fractions. 



It is worthy to note that the percentage of 

 inorganic phosphorus received from the egg 

 was approximately the same as that taken up 

 from the medium, while inorganic phosphorus 

 originating from the sperm was only in -traces 

 present. 



As regards turnover, its rate in respect of 

 phosphorus originating from the medium was 

 the double of that for transmitted phosphorus. 

 Within the latter category, the rate of turnover 

 appeared to be much higher in female than in 

 male imagoes. 



10.20. Induction of Phenocopies in Cosmarium by 

 RNase and Actinomycin D. Robert W. Korn 

 (Kingston, U.S.A.). 



The highly specific shape of the unicel- 

 lular Cosmarium is primarily controlled by a 

 series of chromosomal loci. Over 25 different 

 morphological mutants have been obtained to 

 serve as a basis for a study of phenotypic 

 induction. RNase and actinomycin D treated 

 cells produced daughter cells which manifested 

 both shape and symmetry alterations similar 

 to mutant types. These phenocopies differed 

 from mutant lines by persisting for only one 

 cell generation. Actinomycin D produced a 

 higher frequency and a wider range of types 

 than RNase. RNase frequently inhibited all 

 differentiation while Actinomycin D usually 

 affected only one distinct step. Preliminary 

 evidence indicates these changes are induced over 

 the final two hours before cell differentiation. 

 Considerations of time, distribution, and organ- 

 ization of morphogenetic RNA will be presented. 



175 



