Section 6 — Cytology 



combining mutations currently maintained at 

 the National Science Foundation-supported 

 Drosophila Stock Center in Philadelphia with 

 specific chromosomal disarrangements induced 

 by radiation in experiments precisely designed 

 for such purposes. These include: "multi-pur- 

 pose'* strains for detecting chromosome loss, 

 sex-linked recessive lethal mutations, trans- 

 locations, and mutations at 8 specific loci in the 

 offspring of the same treated flies; improved 

 methods for detecting mutations arising in the 

 female germ line; strains for determining the 

 genetic components of somatic damage induced 

 by low doses of radiation; stocks for detecting 

 mutations arising at 20 specific loci in the female 

 germ line and at 37 specific loci arising in the 

 male germ line; a method for determining how 

 often homologous loci mutate simultaneously 

 following various types of treatment ; several ring- 

 shaped X chromosomes containing portions of 

 the Y chromosome; several ring-shaped Y 

 chromosomes with and without visible markers; 

 new marker-inversion stocks for "isogenizing" 

 the whole (or parts of the) genome; and combi- 

 nations with visible effects in the immature 

 stages to facilitate recognition of different ge- 

 notypes during very early life for developmental 

 studies. 



Diagrams of these stocks and techniques, the 

 manner in which they can be utilized, and the 

 applicability of the principles in methodology 

 involved to other organisms will be shown. 



This work has been supported by grant 

 G14148 from the U.S. National Science Foun- 

 dation. 



Information Service ("■) has been utilized for the 

 following projects: 



1. Additional evidence was obtained that 

 ring-shaped chromosomes in Drosophila are 

 highly susceptible to loss following irradiation 

 as shown by their breakage and frequent involve- 

 ment in anaphase bridges. This is in agreement 

 with our previous results derived from breeding 

 tests and confirms our preliminary cytological 

 observations. These effects can be demonstrated 

 even after the cells have been exposed to relatively 

 low doses of rays. 



2. Examination of the somatic cells of Dro- 

 sophila larvae which had been fed chemical mu- 

 tagens (e.g. urethane, nitrogen mustard) or 

 compounds currently under investigation as 

 "chemosterilants"(e.g. "Mapo":tris(l-(2-methyl 

 aziridinyl) phosphine oxide) by the U.S. Depart- 

 ment of Agriculture have revealed the presence 

 of fairly large numbers of broken chromosomes. 

 In line with the theoretical considerations con- 

 cerning the mode of action of such alkylating 

 agents as the lattei, these results tend to indicate 

 that chemicals which are capable of causing 

 sterility in insects act primarily via the induction 

 of genetical damage. 



3. Analyses of structurally altered X and Y 

 chromosomes, particularly newly-synthesized 

 ring-shaped chromosomes, in Drosophila. 



4. Karyotypic analyses of the housefly (Musca 

 domestica) and the honey bee (Apis melliferd). 



5. Detection of the Barr body in human buccal 

 smears (by the use of some portions of the 

 technique only). This method yields preparations 

 which are relatively less distorted than slides 

 made by the techniques currently in use (e.g. 

 thionine, cresyl violet). 



Data, slides, and photomicrographs illustrating 

 these areas of research will be shown. 



6.48. (D.) Cytological Observations on Drosophila 

 and Human Material. I. I. Oster, G. Balaban 

 and R. Binnard (Philadelphia, U.S.A.). 



A modified method for observing somatic 

 chromosomes recently described in Drosophila 



This work has been supported by grant 

 G 24261 from the U.S. National Science Foun- 

 dation and grant AT(30-1)-2618 from the U.S. 

 Atomic Energy Commission. 

 1. Oster. I. I. and G. Balaban No. 37, 

 142-144 (1963). 



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