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A Chovnick

Publications and source records attributed to A Chovnick.

70 records · Page 4Linked to original sources
PubMed1974

Genetic limits of the xanthine dehydrogenase structural element within the rosy locus in Drosophila melanogaster.

Experiments are described that provide an opportunity to estimate the genetic limits of the structural (amino acid coding) portion of the rosy locus (3:52.0) in Drosophila melanogaster, which controls the enzyme, xanthine dehydrogenase (XDH). This is accomplished by mapping experiments which localize sites responsible for electrophoretic variation in the enzyme on the known genetic map of null-XDH rosy mutants. Electrophoretic sites are distributed along a large portion of the null mutant map. A cis-trans test involving electrophoretic variants in the left- and right-hand portions of the map leads to the conclusion that the entire region between these variants is also structural. Hence most, if not all, of the null mutant map of the rosy locus contains structural information for the amino acid sequence of the XDH polypeptide. Consideration is given to the significance of the present results for the general problem of gene organization in higher eukaryotes.

Aldehyde Oxidoreductases↗
PubMed1973

Gene conversion and transfer of genetic information within the inverted region of inversion heterozygotes.

Prior studies of recombination which monitor exchange events in exceedingly short intervals (i.e., separable sites within a cistron) reveal that the basic event in recombination involves a non-reciprocal transfer of information, termed conversion. As a logical consequence of the model suggested by the work in Drosophila, the present investigation examined recombination between rosy mutant alleles (ry:3-52.0) in Drosophila melanogaster in a paracentric inversion (In(3R)P(18)) heterozygote, which placed the rosy region approximately at the center of the inverted region. Comparison of the results of this study with experiments carried out in standard chromosome homozygotes reveals a dramatic suppression of classical crossovers between the rosy mutant alleles in the inversion heterozygote. However, conversions continue to occur for all rosy mutant alleles in all heterozygous combinations in the inversion heterozygote. Moreover, the order of magnitude of conversion frequencies seen in the inversion heterozygote does not change from that seen in the standard chromosome homozygote study. The significance of these observations with reference to the role of rearrangements as barriers of information transfer is discussed. Particular attention is directed to the elaborate inversion polymorphisms seen in natural populations, and to notions concerning their role in the evolution of adaptive gene complexes.

Animals↗
PubMed1970

Studies on genetic organization in higher organisms. II. Complementation and fine structure of the maroon-like locus of Drosophila melanogaster.

Mutants of the maroon-like complex, representative of the five known complementation classes, were subjected to fine structure mapping experiments utilizing a nutritional selective procedure which permits the survival of rare ma-l(+) progeny from large-scale crosses. The analysis provides an internally consistent, unique map, colinear with the complementation map. Noncomplementers exhibit a polarized mapping distribution. In addition to ma-l(+) recombinants, the selective medium permitted the survival of ma-l(+) exceptionals not associated with recombination for adjacent markers. Analysis of the exceptionals favors their origin as convertants.

Animals↗