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V A Ratner

Publications and source records attributed to V A Ratner.

8 recordsLinked to original sources
PubMed1992

Induction of the mobile genetic element Dm-412 transpositions in the Drosophila genome by heat shock treatment.

Males of a Drosophila melanogaster isogenic line with a mutation of the major gene for radius incompletus (ri) were treated by standard light heat shock (37 degrees C for 90 min) and by heavy heat shock (transfer of males from 37 degrees C for 2 hr to 4 degrees C for 1 hr and back; this procedure was repeated three times). In the F1 generation of treated males mated with nontreated females of the same isogenic line, mass transpositions of copia-like mobile genetic element Dm-412 were found. The altered positions of the element seem nonrandom; five "hot spots" of transposition were found. Probabilities of transpositions were estimated after light heat shock and heavy heat shock and in the control sample. These probabilities were, respectively, 3.4 x 10(-2), 8.7 x 10(-2), and less than 4.1 x 10(-4) transpositions per genome per occupied position per generation. Therefore, as a result of heat shock treatment, the probabilities of transpositions were two orders of magnitude greater than those of the control sample in the next generation after induction. Comparison of the results with those after stepwise temperature treatment shows that the induction depends on the intensity of the stress action (temperature treatment) rather than on the type of the stress action.

Animals↗
PubMed1992

[Mobile genetic elements and quantitative characters in Drosophila: facts and hypotheses].

This review is dedicated to the comparison of the facts obtained and the proposed hypotheses, to the critical analysis of the situation arisen, and to the estimation of key propositions of the concept developed. The main point is that mobile genetic elements (MGEs) participate directly in expression, variability, selection and evolution of different quantitative characters. Genetic and selection data are considered, and hypotheses of random fixation, marker effect and direct participation of MGE patterns in expression and selection of quantitative characters are discussed. The consequences of temperature treatment are considered and hypotheses of masked selection and temperature induction of transpositions are discussed. The marker effects are shown to be non-sufficient to explain the properties of quantitative character radius incompletus system. The MGE patterns are important components of genetical system of determination of a quantitative character. MGEs modify, enhance the expression of neighbouring polygenes. Temperature effects could be explained by the influence of stress temperature treatment through the system of heat shock response on the capacity of MGEs to transcribe and transpose. The system of diversed MGE patterns in drosophila chromosomes could be believed to be universal genomic system of "soft" modification of the polygenic control of any limiting quantitative characters.

Animals↗
PubMed1992

[The role of mobile genetic elements (MGE) in microevolution].

The MGEs of Drosophila and other objects contain open reading frames (ORFs) encoding transposition enzymes, and "motifs" similar to functional sites: promoters, enhancers, heat shock regulatory sites, those of reception of different stress external signals and hormones, recombination sites, etc. In other words, MGE play a role of "movable cassettes of regulatory elements" in the genomes. The patterns of genome MGE localization are the important components of polygenic systems of character expression, the subjects of variation and evolution. The summed up density of MGE localization along the genome has probably the upper value corresponding to approx. 1 MGE copy per gene. The transpositional variability of MGE patterns could be random, non-random, self-related and inducible. The MGE patterns are important subjects of microevolution and reconstruction of trees of the pattern similarity is an effective method for its description. The patterns could be changed by selection of limited quantitative characters. The stress induction (temperature, treatment, dysgenic cross, etc.) stimulated the MGE transpositions and excisions, mass in population and multiple in individuals. The temperature induction acts probably through the system of response to heat shock treatment. The totality of MGE patterns make up the genomic system capable of quick reorganizations after stress external and genomic influences. The stress external influences are often correlated with passing of the population through the "bottle-neck" stage. The rate of transpositions has an upper limiting border, so named "boundary of regulation error catastrophe", that corresponds to approx. 1 transposition per genome, per generation. After the stress induction of transpositions this boundary could be exceeded, the state of the population norm becoming disrupted. The changes in MGE patterns are also supposed to accompany the changes of characters of isolation, i.e. to accompany the speciation.

Animals↗
PubMed1991

[Transposition induction of the mobile genetic element Dm412 in the Drosophila genome using heat shock].

Males of Drosophila melanogaster isogenic line with oligogene mutation radius incompletus (ri) were exposed to standard heat-shock (SHS: t = 37 degrees C, 90 min) and heavy heat-shock (SHS: three-fold transfer of males from t = 37 degrees C, 2h, t0t = 4 degrees C 1 h, and back). At F1 of the treated males with untreated females of the same isogenic line mass transpositions of MGE Dm412 were found. The new positions of MGE seem to be not random, and 5 "hot sites" of transpositions were detected. The probabilities of transpositions were estimated after SHS and HHS and in control sample. They were, correspondingly, 3.4 x 10(-2), 8.7 x 10(-2) and less than 4.1 x 10(-4) transpositions per genome, per site occupied, per generation. Therefore, as a result of HS treatment, the probabilities of transpositions were two orders of magnitude increased as compared to control, directly at next generation after induction. Comparison of these results with those obtained after step-wise temperature treatment shows that induction is dependent rather of "stressor effect" of temperature treatment than of treatment way used.

Animals↗
PubMed1976

A cybernetic approach to the origin of the genetic coding mechanism. I. Methodological principles.

It is postulated that some quasi-deterministic code features (universality, connectedness, systematic degeneracy, symmetry, regularity and so on) resulted from unique (and therefore universal) relization of a stochastic evolutionary process. The evolution of real genetic systems should satisfy the principle of succession; that is, loss of a feature that is necessary for a genetic system means death to its carrier. The hypothesis of unique key coincidence is proposed which indicates the mechanisms of arising of the primary correspondence between the linear structures of polynucleotides and polypeptides. If the collinear coincidence was to appear in the key positions of pra-protein with, at least, some of the primitive properties of the pra-amino-acyl-t-RNA-synthetase required for the accelerated recognition of the key positions of pra-template, the positive feed-back mechanism in the system would be most short-circuited so that the repetitive reproduction of pra-synthetase would be much accelerated.

Amino Acyl-tRNA Synthetases↗
PubMed1976

A cybernetic approach to the origin of the genetic coding mechanism. II. Formation of the code series.

The sequential fulfillment of the principle of succession necessarily guides the main steps of the genetic code evolution to be reflected in its structure. The general scheme of the code series formation is proposed basing on the idea of "group coding" (Woese, 1970). The genetic code supposedly evolved by means of successive divergence of pra-ARS's loci, accompanied by increasing specification of recognition capacity of amino acids and triplets. The sense of codons had not been changed on any step of stochastic code evolution. The formulated rules for code series formation produce a code version, similar to the contemporary one. Based on these rules the scheme of pra-ARS's divergence is proposed resulting in the grouping of amino acids by their polarity and size. Later steps in the evolution of the genetic code were probably based on more detailed features of the amino acids (for example, on their functional similarities like their interchangeabilities in isofunctional proteins).

Amino Acids↗