Section 10 — Developmental Genetics 



has been studied by comparison of the response 

 of WW V and normal ww mice to erythropoietic 

 stimulation, as measured by Fe 59 incorporation 

 in erythrocytes. Adult WW V mice and normal 

 littermate controls were plethorized by trans- 

 fusion with C57BL/6 erythrocytes to hematocrit 

 levels of 60 per cent or higher, in order to 

 repress erythropoiesis and inhibit formation of 

 endogenous erythropoietin. Purified exogenous 

 erythropoietin, made available through the 

 kindness of Drs. G. Keighley and P. H. Lowy of 

 the California Institute of Technology, was then 

 administered to half the animals of each geno- 

 type. The response of animals of the two geno- 

 types to this stimulus was compared by measure- 

 ment of Fe 59 incorporation in erythrocytes 24 

 hours and 72 hours after Fe 59 injection. Pleth- 

 orized animals of both genotypes, without 

 erythropoietin, exhibited very low levels of Fe 59 

 uptake. Erythropoietin increased the rate of 

 incorporation of Fe 59 in mice of both genotypes, 

 but the increase in rate was much greater in the 

 normal than in the WW X mice. It is apparent that 

 WW V mice are not incapable of responding to 

 erythropoietic stimulation, as previous investi- 

 gations had suggested, but that they differ from 

 normal mice in degree of response. This new 

 finding implies that the ff-genes affect the rate 

 and end-point of the response to erythropoietin, 

 but do not inhibit its onset. 



This investigation was supported by a Grant 

 (He-05748) from the National Heart Institute, 

 U.S. Public Health Service. 



10.53. Effect of Folic Acid Inhibitor upon Morpho- 

 genesis of the Wings of vestigial Heter- 

 ozygotes in Drosophila. J. David (Lyon, 

 France). 



When added to an axenic medium, aminop- 

 terin slows larval growth a little, but the adult 

 morphogenesis of the wild strains remains 

 normal. When vestigial (vg, 2rd chromosome 

 heterozygotes are reared with the above- 

 mentioned medium, the wings of the flies are not 

 normal and present some notches on the border. 

 This result appears to signify an imperfect 

 dominance of the wild type gene over its vestigial 

 allele and suggests that, in the heterozygous 

 condition, vg alters the folic acid metabolism in 

 the imaginal disc of the wing. 



10.54. Variability of Sex Ratio and Sex-determining 

 Mechanism in Asellus. G. Montalenti and 

 G. Vitagliano Tadini (Rome, Italy). 



10.52. Analysis of Gene Action and Characterization 

 of a New Hematological Abnormality, Hemoly- 

 tic Anemia. Seldon E. Bernstein (Bar 

 Harbor, U.S.A.). 



This paper describes a new mutation in the 

 house mouse called hemolytic anemia (symbol 

 ha). Evidence is presented indicating that the 

 hemolytic condition results from the action of an 

 autosomal recessive gene at a locus as yet not 

 located in any of the 20 known linkage groups. 

 This blood dyscrasia is characterized as being a 

 severe neonatal hypochromic microcytic anemia, 

 resulting neither from a maternal-fetal incom- 

 patibility nor from the presence of an abnormal 

 hemoglobin. Erythroblastosis, jaundice, sple- 

 nomegaly, and cardiac hypertrophy are promi- 

 nent features. Homozygotes of hemolytic anemia 

 (liaha) resemble in nearly every detail jaundiced 

 homozygotes (jajd). Genetic evidence will be 

 presented, however, which will show that the 

 two conditions are caused by unrelated genes. 

 An analysis of the action of hemolytic anemia 

 genes in terms of a pedigree of causes will follow. 



In Asellus aquaticus sex ratio shows a great 

 statistically significant variability between the 

 progeny of different pairs, the total ratio of the 

 population is approximately 1: 1. In the popu- 

 lation of the river Sarno (Naples) the percentage 

 of males in different sibships varies from per 

 cent (absolute thelygeny) to 95 per cent (high 

 androgeny) with higher frequencies toward 50 per 

 cent ("normal" s.r.). The distribution is of the 

 gaussian type. Sex is genetically determined and 

 so is this variability; intersexuality or hermaphro- 

 ditism do not occur with appreciable frequency; 

 parthenogenesis does not occur. In previous 

 papers the authors have put forward, as a first 

 approximation, the hypothesis that sex in 

 Asellus is under control of a series of polygenes, 

 with the assumption of a clear-cut threshold 

 effect between maleness and femaleness. Further 

 experiments however failed to bring evidence in 

 favour of the loose recombination of a number of 

 genes. A modification of the former hypothesis 

 is proposed, which requires a limited number of 

 genes and assumes that they are more or less 

 closely linked. Three pairs of genes (or gene 

 blocks) would be involved, two (A, B) closely 

 linked, a third (Z) more loosely linked with the 

 former two. Two female genotypes would 



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