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Luning., K. G., Lake, S. and Linde, M. 1984. Genetics of inbred Drosophila melanogaster XII. Effects of an X-chromosome inversion on primary and secondary non-disjunction.—-Hereditas 100: 247–257. Lund, Sweden. ISSN 0018–0661. Received August 1, 1983 In an inbred line of Drosophila melanogaster. Oregon (code 2), an inversion covering the proximal half of the X-chromosome was induced (symbol: In(l) Lu-l y wd cxvf-2). It has been shown that inversion homozygotes have low frequencies of primary nun-disjunction. in the same manner as equilinear females with regular gene order of the 2–line. Intra-strain structural heterozygotes gave an excess of XO exceptionals but also a 5–fold increase of true primary non-disjunction (XXY) as compared to structural hornozygotes. Inter-strain crosses with mothers from line “K” revealed an influence both by the maternal genome and by the origin of the cytoplasm. Tests of secondary non-disjunction in structural heterozygous XXY females from both intra- and inter-strain crosses indicated highly complicated relations. When the mothers were of “2” origin the first brood showed lower frequencies of XXY exceptionals than in successive broods. whereas when the mother was of “K” origin there was a decrease after the 3rd brood (7th day). The “K”-line showed a dominance effect which was manifested by higher frequencies of XXY exceptionals. In regular daughters the Y-chromosome followed preferentially the proximal part of the X-chromosome of “K”. origin. There was no preference in the Y-chromosome distribution in intra-strain hybrids. There was a pronounced low frequency of recombinants among exceptionals. This indicates that the high frequencies of exceptionals from inversion heterozygous XXY females occur by another mechanism than in equilinear XXY females with the same genetic background.

The carbonic anhydrase isozymes (CA I and CA II) of the pig-tailed macaque, Macaca nemestrina , have been chosen to study the regulation of enzyme levels in red blood cells. Two quantitative variants of CA I that are ideal for studies of enzyme regulation exist in this species. One variant is one of four known electrophoretic types of CA I, designated CA Ia, which is present at levels about 30% of those of the other electrophoretic types. The other is a deficiency variant of CA I which, in homozygotes, reduces the product of the CA I locus about 5000-fold and reduces the product of the CA II locus by about 60%. l -[ 14 C]Serine was used to study the biosynthesis of CA I and CA II isozymes in the reticulocytes of animals carrying these CA I variants. Specific radioactivity and total incorporation data from bone marrow erythroid cells, and peripheral blood reticulocytes indicate that the reduced CA Ia concentration is probably the result of degradation. This degradation appears to occur for only a short time before the reticulocytes enter the peripheral blood. It was not possible to determine whether the 5000-fold reduction of CA I in the CA I-deficient animals is due to reduced transcription, reduced translation, or degradation. The effect of the CA I-deficiency mutation on the synthesis of CA II was also studied. For each dose of CA I-deficiency gene, there appears to be a 30% reduction in the rate of l -[ 14 C]serine incorporation into CA II, thereby accounting for the reduced CA II concentration in CA I-deficient animals.