Section 10 — Developmental Genetics 



by a larger number of undeveloped eggs. The 

 variation in proportions of undeveloped, ab- 

 normal and normal embryos in different col- 

 lections of eggs from one female or among 

 females suggests a threshold response to an 

 undetermined physiological or environmental 

 factor. 



The genetic factor or factors that produce the 

 bicaudal effect appear to be associated with 

 the unmarked second chromosome present in 

 all three CyL 4 sp-/+ + + inbred stocks. The 

 maternal, but not paternal, chromosomes in- 

 fluence the formation of these embryonic ab- 

 normalities. 



10.12. Phenogenetics of the lozenge Loci in Droso- 

 phila melanogaster. Harvey A. Bendkk and 

 M. M. Green (Davis, U.S.A.). 



The pleiotropic effects of the sex linked 

 lozenge (Iz) mutants include such seemingly 

 unrelated features as: modification of eye color, 

 structure, and size; absence of spermathecae and 

 parovaria; and reduced tarsal claws. Recent 

 studies (Bender and Green, 1 962) have, in 

 addition, demonstrated primary ovarian histo- 

 pathologies in the /~ 34k and lz 34k ; su(3) fe 84k 

 mutants. Such investigations have been extended 

 to include lozenge mutants representative of each 

 of the four sub-loci demonstrated in the Iz 

 pseudoallele complex, and to flies compounded 

 in all possible permutations with such alleles. 



Utilized were studies of fertility, fecundity, egg 

 hatchability and viability, as well as histological 

 and histochemical analyses of the primary and 

 secondary reproductive tissues. The ovarian 

 investigations were implemented with whole 

 mount as well as paraffin sectioned preparations 

 and included transplanted tissues. The histochem- 

 ical studies detailed nucleic acid, carbohydrate, 

 protein and lipid localizations. 



Evidence was obtained linking the imaginal 

 corpus allatum with the primary cause of Iz 

 ovarian abnormalities. 



This work was supported in part by National 

 Institutes of Health Grant No. GM 08697-02 

 and by Atomic Energy Commission Research 

 Contract AT (I l-l)-38. 



D. gyrociliatus under constant environmental 

 conditions suggests a special mechanism of sex 

 determination. There is a non random distri- 

 bution of big female and small male eggs in the 

 egg capsules. The two types of eggs in their 

 production in the ovary depend on each other in 

 a way that resembles genetic segregation. But 

 this segregation must take place before a stage in 

 which meiosis was demonstrated by Nachtsheim 

 (1919) and Shen (1936). 



10.14. Pigment and Pleiotropism: Combined Effects 

 of Ww/ww and ff/Ff Gene Substitutions. 

 Elizabeth S. Russell (Bar Harbor, U.S.A.). 



Many different mutant genes in the mouse, 

 including W and f combine effects on distri- 

 bution of pigment in the hair-coat with patho- 

 logical effects in other tissues. A hyperadditive 

 interaction of Ww/ww and ff/Ff genie substitutions 

 in restriction of pigmentation has been demon- 

 strated through quantitative evaluation of 

 percent white-spotting in littermate animals of 

 four genotypes, Wwff (40 per cent white), WwFf 

 (II per cent white), wwff ( 14 per cent white) and 

 wwFf (solid black). All spotting variation was 

 attributable to these segregating genes, since the 

 animals were otherwise highly congenic with the 

 FL/Re inbred strain. The ///fY" substitution has a 

 significant effect on fetal and newborn blood- 

 picture, leading to a microcytic, siderocytic 

 anemia, more severe at 14-16 days gestation than 

 at birth, and completely cured by two weeks 

 postnatal. Although WW fetuses and newborn 

 mice are lelhally anemic, newborn WwFf and 

 Wwff individuals have higher erythrocyte counts 

 than do corresponding wwFj and wwff individuals, 

 and fetal anemia associated with Ww/ww is very 

 improbable. It is conceivable that severe fetal 

 anemia, resulting from //'gene-action, could have 

 resulted secondarily in ventral white-spotting 

 by inhibiting late stages of melanoblast mi- 

 gration. It is highly unlikely, however, that cither 

 the ventral while-spotting of WwFf mice or the 

 great increase in white area of Wwff over wwff 

 mice is in any way related to defective fetal 

 blood supply. The results may better be ex- 

 plained by tissue-localized effects of Ww/ww, 

 and probably also ff/Ff, gene substitution acting 

 independently in mclanoblasts and in hemato- 

 poietic cells. 



10.13. A New Approach to the Problem of Sex 



Determination in Dinophilus. Walther Traut 10.15. Interactions at the Agouti Locus. M. M. Dickie 



(Saarbrucken, Germany). (Bar Harbour, U.S.A.). 



An analysis of egg capsules deposited by 



The agouti locus in the mouse now has nine 



173 



