bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gross karyotypic change and evolution in North American cyprinid fishes
Authors: Gold J. R. , Womac W. D. , Deal F. H. , Barlow J. A. 
Published: September 2009

SUMMARYWe have examined karyotypes of five species from five genera of cyprinid fishes endemic to the central and southeastern United States: Campostoma anomalum, Hybognathus hayi, Hybopsis aestivalis, Phenacobius mirabilis, and Pimephales vigilax. All five have a diploid chromosome number of 50. Variation in chromosome arm number among the five species is slight, and may be due to measurement error or technique difficulties. The karyotypes of 40 North American cyprinids are now known. All but five species have 50 (diploid) chromosomes. Variation in chromosome arm number also appears minimal; one-armed chromosomes (centromeres subterminal to terminal) normally comprise only a small fraction of the karyotype, and each species has roughly the same number of chromosomes with median and submedian centromeres. The conservatism of gross chromosomal evolution among these fishes is not in accord with recent hypotheses which suggest that progressive evolution of organisms may depend to a large degree on gene rearrangement brought about by gross chromosomal restructuring. Cyprinids are a highly speciose group in North America, and there is relatively strong morphological differentiation among species. The present data suggest that gross chromosomal restructuring may play only a minor role in the speciation and evolution of these fishes.
Allozyme polymorphism in the parasitic hymenopteraDiadromus pulchellusWSM. (Ichneumonidae)
Authors: Shaumar Nagat , Rojas-Rousse Danielle , Pasteur Nicole 
Published: September 2009

SUMMARYThe allozyme polymorphism ofDiadromus pulchellushas been analysed at 22 loci, the expression of one (Est-4) being male-limited. Six loci were found polymorphic for two (Ldh-1,Ldh-2,Acp-2,PgiandSdh) or three (Est-3) codominant alleles. Allele frequencies are similar in males and females at four loci in a laboratory population but there are important heterozygote deficiencies in females at three of them. The possibilities of negative heterosis or assortative mating to explain this deficiency are discussed.
Studies on the sterility induced by the male recombination factor 31.1 MRF inDrosophila melanogaster
Authors: Yannopoulos George 
Published: September 2009

SUMMARYThe sterility which is associated with male recombination induced by 31.1 MRF was studied genetically and cytologically. In all crosses it was found that female sterility mainly involves failure of the heterozygous females to lay eggs because their ovaries are atrophic. Under the optical microscope, the atrophic ovaries were seen to contain only germaria in their ovarioles. It was also found that in some cases 31.1 MRF affects only one of the two ovaries of the same female. This observation suggests that defective development of atrophic ovaries is not due to influences from the rest of the body but should be attributed to the inability of the germ cells to differentiate. Moreover, various stocks as well as homologous chromosomes were found to react differently to 31.1 MRF with respect to female sterility. In their effect on male sterility it was observed that some strains behave as neutral and others as reactive when mated with 31.1/Cy L4males.
Effects of therexgene of phage λ on lysogeny
Authors: Campbell J. H. , Dykhuizen D. , Rolfe B. G. 
Published: September 2009

SUMMARYMutations in therexgene of phage λ affect lysogeny. λrex−phages have an increased probability of forming abortive lysogens instead of stable lysogens. In addition, established lysogens produce elevated levels of cured cells during anaerobic but not aerobic growth. It is suggested that the function of therexgene is related to excision or repressor function.
Naturally occurring strains ofSalmonella paratyphi Bunable to form adhesive (type-1) fimbriae
Authors: Old D. C. 
Published: September 2009

SUMMARYThe production of MSHA+(type-1 fimbriate) recombinants was observed in transductional crosses between different pairs of naturally occurring strains ofSalmonella paratyphi B. MSHA+recombinants were readily produced in transductions from MSHA+donor strains to MSHA−(type-2 fimbriate or non-fimbriate) recipient strains, and less frequently between some pairs of MSHA−strains. The genetic evidence suggests that there are at least three different clones among MSHA−strains ofS. paratyphi B. Relationships between the different strains and their possible origins are discussed.
Coordination on timing of gene expression inParamecium
Authors: Myohara Koji 
Published: September 2009

SUMMARYInParamecium caudatum, syngen 3, cells become mature (i.e. capable of undergoing conjugation) by about 50 fissions after conjugation. Matingtype-instability, another mating characteristic, begins to occur between 80 and 120 fissions after conjugation in heterozygotes for the mating type locus (Myohara & Hiwatashi, 1975). Mating-type instability also occurs in dominant homozygotes, earlier than in heterozygotes. In two different early maturing mutants the homozygotes become mature 20 fissions earlier than in wild-type clones, and mating-type instabiliiy also begins earlier than in wild-type clones. The number of fissions from maturity to the occurrence of the mating type change does not differ.
A major autosomal gene effect on activity of glucose 6-phosphate dehydrogenase segregating between recombinant inbred lines of mice
Authors: Erickson Robert P. , Harper Kenneth 
Published: September 2009

SUMMARYG6PD measurements (expressed per g haemoglobin) in both males and females of the parental lines C57BL/6J and C57L/J and four recombinant inbred (RI) lines between them showed segregation of G6PD levels as parental classes (one line showed the higher C57BL/6J activity, three lines were indistinguishable from C57L/J). Haemoglobin also varied significantly among the parental and RI lines but this variation did not explain the variation in G6PD. NADP levels (expressed per g wet wt of erythrocytes) correlated with G6PD levels but one RI line was intermediate in males while two RI lines were lower than either parental line in females. Thus, the major autosomal locus affecting G6PD levels which segregates between these two inbred lines probably does not act directly on NADP levels. The variation in the G6PD levels in the four RI lines co-segregated with the brown coat color locus but the association is not significant because of the small number of RI lines available.
Distribution of human chromosomes on the metaphase plate. Symmetrical arrangement in human male cells
Authors: Coll M. Dolores , Cuadras Carlos M. , Egozcue Jose 
Published: September 2009

SUMMARYTwo linear models have been devised and applied to the study of the distribution of human male chromosomes on the metaphase plate in preparations from lymphocyte cultures not treated with spindle poisons. Using these it has been found that the chromosomes are approximately distributed around a centre of symmetry and that the lines joining the centromeres of homologous chromosomes (i.e. segments) have the centre of symmetry approximately at their mid-point. Thus each chromosome mirrors the position of its homologue relative to the centre of symmetry. The position of each chromosome in the metaphase plate was found to be approximately constant relative to the centre of symmetry and the other chromosomes. The significance of these findings is discussed in relation to the hypothesis on the distribution of the chromosomes in interphase nuclei and to data on acrocentric associations, acrocentric-non-acrocentric associations and the frequency of the most common translocations.
Thymineless elimination of N group plasmids is Res−(RII)-dependent and determined by a different gene than the Uvp plasmid phenotype
Authors: Tribe M. J. , Pinney R. J. 
Published: September 2009

SUMMARYThe wild-type N group plasmid RN3, which is phenotypically Res+Mod+(RII) is not eliminated by thymine starvation of its bacterial host. Derivatives of RN3 selected for the Res−phenotype are eliminated. The presence or absence of the RII modification specificity does not affect thymineless elimination of RN3 Res−plasmids. A Res−Mod(am) RN3 mutant is not eliminated by thymine starvation from either amber suppressing or non-suppressing hosts, suggesting that it carries a cryptic mutation in a novel genetic locus required for elimination. Thymineless elimination is shown to berecA+-dependent and the presence of the X group plasmid R6K significantly inhibits elimination of RN3 Res−Mod+. However, since R6K has no effect on two other plasmid-mediated functions of UV protection and UV-induced mutagenesis, which are alsorecA+-dependent, it would appear that elimination is determined by a separate plasmid gene than that encoding the UV functions. This is confirmed using derivatives of another N group plasmid R390, which eliminate but which have lost the ability to increase UV-induced mutagenesis in their host.
Genetic variation in varying environments
Authors: Mackay Trudy F. C. 
Published: September 2009

SUMMARYIn order to assess the relationship between genetic and environmental variability, a large natural population ofDrosophila melanogasterwas replicated as eight subpopulations, which were subjected to four different patterns of environmental variation. The environmental variable imposed was presence of 15% ethanol in the culture medium. Experimental treatments of the populations were intended to simulate constant environmental conditions, spatial heterogeneity in the environment, and two patterns of temporal environmental variation with different periodicity (long- and short-term temporal variation). Additive genetic and phenotypic variation in sternopleural and abdominal chaeta number, and body weight, were estimated in two successive years, and measurements were taken of the genotype–environment correlation of body weight and sternopleural bristle score with medium type.Additive genetic variance of sternopleural chaeta number and of body weight was significantly greater in the three populations experiencing environmental heterogeneity than in the control population, but additive genetic variance of abdominal bristle score was not clearly affected by exposing populations to varying environments. Temporal environmental variation was equally, if not more, efficient in promoting the maintenance of genetic variation than spatial heterogeneity, but the cycle length of the temporal variation was of no consequence. Specific genotype–environment interactions were not present, therefore adaptation to heterogeneous environments is by selection of heterozygosityper se, rather than by differential survival of genotypes in the alternate niches.
Reduced pigmentation (rp), a new coat colour gene with effects on kidney lysosomal glycosidases in the mouse
Authors: Gibb S. , Håkansson E. M. , Lundin L.-G. , Shire J. G. M. 
Published: September 2009

SUMMARYA spontaneous autosomal mutation in C57BL/Tb mice, provisionally called reduced pigmentation, symbolrp, has pronounced effects on three kidney lysosomal glycosidase activities. Homozygousrprpmice have significantly higher activities of β-galactosidase, β-glucuronidase andN-acetyl-β-hexosaminidase than their heterozygous litter-mates. Homozygotes have light ears and tails, diluted fur and dark eyes. The mutation is not allelic to any known to affect lysosomal functions, or to a number of pigmentation variants with similar phenotypic effects. The locus is on chromosome 7.
Spatio-temporal microdifferentiation of water-strider (Gerris) populations
Authors: Varvio-Aho Sirkka-Liisa , Pamilo Pekka 
Published: September 2009

SUMMARYSpatial and temporal differentiation inGerris lacustrisandG. odontogaster(Heteroptera, Gerridae) were studied in restricted areas, where one population of each species was subdivided into several subpopulations. The aim of the study was to relate genetic population parameters to ecological population structure studied by mark-recapture methods in the same pond systems. Marked differentiation between the subpopulations and significant enzyme allele frequency changes between subsequent generations were found at several loci. It is suggested that non-selective forces are a sufficient explanation for the observed differences.
Comparative studies of two male recombination factors (MRF) isolated from a Southern GreekDrosophila melanogasterpopulation
Authors: Stamatis Nikos , Yannopoulos George , Pelecanos Michael 
Published: September 2009

SUMMARYA comparative study of two male recombination factors (31. 1 MRF and 23. 5 MRF) isolated from the same Southern Greek natural population, revealed specific differences in their activities. 23. 5 MRF induces female sterility due to atrophie ovaries at a wide range of temperatures while 31. 1 MRF does so only at high temperatures. The gross morphology of the atrophie ovaries was the same and unilaterally affected pairs were found in the F1of crosses with both 23. 5 and 31. 1 MRF. Furthermore, 23. 5 MRF induces: (a) lower frequencies of abnormal anaphases I and II than 31. 1 MRF, (b) higher frequencies of ‘double crossovers’ resulting from deficiences or duplications, (c) large clusters of recombinants, suggesting premeiotic origin and (d) cases where one of the non-recombinant phenotypes was not produced. Such cases have never been observed with 31. 1 MRF. Moreover, the cytoplasm of theCy L4/Pmstrain that suppresses 31. 1 MRF does not affect the activities of 23. 5 MRF. Hypotheses to explain the different behaviour of the two factors are presented and discussed.
Galactosyltransferase activities on mouse sperm bearing multipletlethalandtviablehaplotypes of the T/t-complex
Authors: Shur Barry D. 
Published: September 2009

SUMMARYSegregation-distortingt-sperm show a specific increase inN-acetylglucosamine: galactosyltransferase activity over wild-type (+/+) due to a deficiency of a wild-type galactosyltransferase inhibitor (Shur & Bennett, 1979). Eight other enzymic activities are indistinguishable between +- andt-sperm suspensions. In this study, three additional points are analysed. First, galactosyltransferases are assayed on sperm homozygous for a semilethal haplotype (tW2/tW2), relative to heterozygous (+ /tw2) and wild-type (+/+) controls.tW2/tW2assays circumvent the +-sperm inhibition oft-sperm galactosyltransferases that occurs in heterozygous + /t-assays and show thatt-sperm are actually four times as active as wild-type. Second, sperm which are compound heterozygotes for two complementing lethalt-haplotypes (tlx/tly), have nearly twice the theoretical enzyme level oftlx/tlysperm. Thus, in either homozygous (tW2/tW2) or double heterozygous (tlx/tly) formt-haplotypes act synergistically on sperm galactosyltransferase activity.Third, and most interesting, sperm bearing either recombinant, viablet-haplotypes (+/tv,tvx/tvy), or one of three dominantT/t-complex mutations, were assayed to determine which portions of theT/t-complex are responsible for elevated galactosyltransferase activity. Results show that sperm bearing recombinant, non-segregation-distorting, viabletv-haplotypes no longer show elevated transferase activity. Therefore, the elevatedt1-sperm galactosyltransferase activity strictly correlates with the increased transmission frequency oft1-sperm. These studies strengthen further the hypothesis that sperm surface galactosyltransferases are involved in egg binding during fertilization, and thatt1-sperm segregation-distortion results, at least in part, from increased galactosyltransferase activity.
Rapid detection of allelic recombination at thegalllocus in yeast by assay of the recombinant gene product
Authors: Johnston Leland H. 
Published: September 2009

SummaryA diploid heteroallelic at thegal1locus and producing little residual galactokinase activity was chosen. Following either γ- or UV-irradiation, recombination occurred leading to the formation of wild-typeGAL1 genes and an increase in detectable galactokinase. An enhanced level of enzyme was first detectable 2 h after irradiation and reached a maximum within 12–14 h. With increasing doses of irradiation, more enzyme was produced and this increase superficially resembled that obtained for plated recombinants. However, far more enzyme was actually synthesized than expected from the number of viable recombinants in the cells assayed. This suggests that recombination must have occurred in cells without colony-forming ability, indeed it may have occurred more frequently in these cells than in viable cells.
The effects of thet-complex upon male reproduction are due to complex interactions between its several regions
Authors: Hammerberg Craig 
Published: September 2009

SummaryThe three major regions (T, tail-determining; A, abnormal transmission ration; L, embryonic lethality) of thetcomplex on the murine seventeenth chromosome can interact to influence male reproduction (Lyon & Mason, 1977; Hammerberg, 1981). Evidence is presented here that suggests: (1) the presence of a polymorphic system within the T region that influences quasi-sterility in the male; (2) the existence of enhancing factors of transmission ratio distortion; and (3) that preferential interactions betweent-haplotypes are found to occur bothcisandtranswhich influence transmission ratio distortion.
Time until fixation of a mutant belonging to a multigene family
Authors: Ohta Tomoko 
Published: September 2009

SUMMARYTime until fixation of a mutant that occurs in one copy of a multigene family was investigated from the standpoint of population genetics. Because of the complexity of the double process of random drift (on the chromosome and in the population), an approximate method based on the rate of steady decay of genetic variability is applied. The simple model of gene conversion with constant gene family size is also used. The expectation based on the approximate method is shown to be valid by extensive Monte Carlo simulations, and the results are useful for understanding the mechanisms of turnover of multigene families, when comparison is available between closely related species.
Biochemical genetics of Neurospora nuclease I: Isolation and characterization of nuclease (nuc) mutants
Authors: Forsthoefel A. M. , Mishra N. C. 
Published: September 2009

SUMMARYIsolation and characterization of five new nuclease (nuc) deficient mutants ofNeurosporahave been described. The new mutants are unable to utilize nucleic acids as the sole phosphorus source and possess growth characteristics similar to thosenuc(nuc-1andnuc-2) mutants described previously. Two new mutants (nuc-4andnuc-5) were able to use RNA or predigested DNA (but not intact DNA) as phosphorus source and showed temperature sensitive growth at 37 °C. Based on the data from complementation and genetic analyses the five new nuc mutants (nuc-3, nuc-4, nuc-5, nuc-6andnuc-7) were found nonallelic to each other and to previously describednuc(nuc-1andnuc-2) mutants; the newnucmutants mapped to the right ofarg-12on linkage group II. On biochemical analyses, thesenucmutants were found to possess a lower level of extracellular nucleases and alkaline phosphatase as compared to the wild type strain. The ds DNase activity of the new mutants was only about 2–12% of that of the wild type strain; thus, the low level of these extracellular enzymes in thenucmutants causes their inability to utilize nucleic acids as the sole phosphorus source. Wild type levels of these enzymes were restored in the complementing heterokaryons capable of full growth on the DNA medium. Data from intercrosses, mutagen sensitivity and spontaneous mutation-frequency studies (as discussed in a subsequent paper) indicated the involvement of thenucgenes in DNA repair and recombination.
Steroid sulphatase in the mouse
Authors: Lam S. T. S. , Polani P. E. , Fensom A. H. 
Published: September 2009

SUMMARYA form of the human skin disease, ichthyosis, results from a mutation at the steroid sulphatase locus (STS) on the X chromosome. This locus appears to escape inactivation in the XX female, resulting in the expression of two doses of the STS gene (Shapiro et al. 1978; Crawfurd, 1982). The scurfy mutation in the mouse is thought to be homologous to the human disease (McKusick, 1978), and so should also be due to a steroid sulphatase (STS) deficiency. Our findings in male and female mice suggest that, in contrast to the human, the murine ‘STS’ locus is subject to X chromosome inactivation. However, another interpretation of the results is possible, namely that STS may be coded for by an autosomal gene.
Chromosome rearrangements resulting in increased aneuploid production inSordaria brevicollis
Authors: Bond D. J. , Broxholme S. J. 
Published: September 2009

SUMMARYTwo spontaneously arising chromosome rearrangements were isolated inSordaria brevicollisfrom one perithecium. These were detected through increased production of black spores in intercrosses of complementing buff spore colour mutants. One was a reciprocal translocation between linkage groups I and II; the other a reciprocal translocation between linkage groups II and VI. In the former case the translocation resulted in frequent non-disjunction generating black spores which were either tertiary or interchange disomics. The frequency of premature centromere division was also increased. In the case of the translocation involving linkage groups II and VI the black spores were formed as a result of adjacent-1 segregation and were probably duplication/deficiency products.In both rearrangements the breakpoint in linkage group II was, as far as could be judged, in an identical place. This and the fact that they were isolated from a single fruiting body, suggests that the chromosome breakage event arose as a potential lesion, which replicated before the potential break was either restituted, to restore a normal chromosome, or opened, to form the rearrangements.
Segregation of centricY-autosome translocations inDrosophila melanogaster: II. Segregation determinants in females
Authors: Falk Raphael , Rahat Ana , Baker Shula 
Published: September 2009

SummaryThis is a study of the chromosomal segregation patterns in females of 15 Experimental stocks ofDrosophila melanogaster, each carrying one element of a T (Y; 2) with a centric break-point. In each Experimental stock the relative frequency of all eight possible meiotic configurations of four relevant chromosomal elements was followed: an attached-Xchromosome, a multiply-inverted chromosome 2, a free arm of chromosome 2, and a half-translocation element. Although the 15 translocation elements were broken at different sites, there were no basic differences among the Experimental stocks in their segregation patterns. The three two-by-two configurations were the most common. Comparison of this pattern with that of the segregation pattern of stocks similar but for an inversion-free chromosome 2, showed that in the Experimental stocks exchange pairing did not play a significant role in the determination of the segregation pattern.The results of these experiments, together with the analysis of results from other published studies provide evidence against the model that had been forwarded by Grell. According to this model, chromosomes that did not participate in exchange pairing undergo another pairing cycle, in which total chromosome length is a factor in the determination of segregation.We support a modified version of Novitski's model of premetaphase chromocenter-like chromosome aggregation. Disjunction of non-exchange chromosomes is regulated by determinants located in the proximal heterochromatin of the sex chromosomes and the autosomes. However, the specificity, especially that of the autosomal determinants, is not high. Thus, if an autosome and a sex chromosome are available, their determinants may interact-to-disjoin by default. More frequently, the determinants of the left-arm autosomal element may interact-to-disjoin with those of the right-arm chromosomal element.