bluuebunny/crossref_metadata_2025_split huggingface dataset:
RTM1: a member of a new family of telomeric repeated genes in yeast.
Authors: Ness F , Aigle M 
Published: April 2021

Abstract
We have isolated a new yeast gene called RTM1 whose overexpression confers resistance to the toxicity of molasses. The RTM1 gene encodes a hydrophobic 34-kD protein that contains seven potential transmembrane-spanning segments. Analysis of a series of industrial strains shows that the sequence is present in multiple copies and in variable locations in the genome. RTM loci are always physically associated with SUC telomeric loci. The SUC-RTM sequences are located between X and Y' subtelomeric sequences at chromosome ends. Surprisingly RTM sequences are not detected in the laboratory strain X2180. The lack of this sequence is associated with the absence of any SUC telomeric gene previously described. This observation raises the question of the origin of this nonessential gene. The particular subtelomeric position might explain the SUC-RTM sequence amplification observed in the genome of yeasts used in industrial biomass or ethanol production with molasses as substrate. This SUC-RTM sequence dispersion seems to be a good example of genomic rearrangement playing a role in evolution and environmental adaptation in these industrial yeasts.
The diversity of alleles at the hsd locus in natural populations of Escherichia coli.
Authors: Barcus V A , Titheradge A J , Murray N E 
Published: April 2021

Abstract
In enteric bacteria three discrete families of type I restriction and modification systems (IA, IB and ID) are encoded by alleles of the serB-linked hsd locus. Probes specific for each of the three families were used to monitor the distribution of related systems in 37 of the 72 wild-type Escherichia coli strains comprising the ECOR collection. All 25 members of group A in this collection were screened; 12 were probe-positive, nine have hsd genes in the IA family, two in the IB and one in the ID. Twelve strains, representing all groups other than A, were screened; five were probe-positive, one has hsd genes in the IA family, one in the IB and three in the ID. The type ID genes are the first representatives of this family in E. coli, the probe-negative strains could have alternative families of hsd genes. The type IA and IB systems added at least five new specificities to the five already identified in natural isolates of E. coli. The distribution of alleles is inconsistent with the dendrogram of the bacterial strains derived from other criteria. This discrepancy and the dissimilar coding sequences of allelic hsd genes both imply lateral transfer of hsd genes.
Wolbachia infections and the expression of cytoplasmic incompatibility in Drosophila sechellia and D. mauritiana.
Authors: Giordano R , O'Neill S L , Robertson H M 
Published: April 2021

Abstract
Various stocks of Drosophila mauritiana and D. sechellia were found to be infected with Wolbachia, a Rickettsia-like bacterium that is known to cause cytoplasmic incompatibility and other reproductive abnormalities in arthropods. Testing for the expression of cytoplasmic incompatibility in these two species showed partial incompatibility in D. sechellia but no expression of incompatibility in D. mauritiana. To determine whether absence of cytoplasmic incompatibility in D. mauritiana was due to either the bacterial or host genome, we transferred bacteria from D. mauritiana into an uninfected strain of D. simulans, a host species known to express high levels of incompatibility with endogenous Wolbachia. We also performed the reciprocal transfer of the natural D. simulans Riverside infection into a tetracycline-treated stock of D. mauritiana. In each case, the ability to express incompatibility was unaltered by the different host genetic background. These experiments indicate that in D. simulans and D. mauritiana expression of the cytoplasmic incompatibility phenotype is determined by the bacterial strain and that D. mauritiana harbors a neutral strain of Wolbachia.
Spatial distributions of genotypes under isolation by distance.
Authors: Epperson B K 
Published: April 2021

Abstract
The spatial distributions of single-locus diploid genotypes, produced within populations of sexually reproducing individuals under isolation by distance, are measured and characterized in detail by quantifying the join-counts for simulated model populations. The models more realistically reflect spatially explicit distributions of genotypes in populations, because unlike the classical theory, they include the stochasticity inherent in the process of matings between genotypes. This stochasticity causes the formation of large areas or patches containing mostly one homozygous genotype, which is not predicted by the classical theory. A number of previously uncharacterized features of the spatial structures produced under isolation by distance are revealed. Spatial autocorrelation measures based on counts of pairs of homozygotes are highly consistent quantifications of the concentrations of homozygotes in patchy genotypic distributions for a given level of dispersal. Most strikingly, the degree of intermixing of homozygotes with heterozygotes over small spatial scales is much higher than previously thought, unless dispersal is extremely limited (e.g., Wright's neighborhood size less than approximately 5.0). Among implications for studies of spatial structure of real populations, one is that the results provide a basis for using join-counts as estimators of gene dispersal based solely on genetic data.
GENETIC LOAD AND VIABILITY DISTRIBUTION IN CENTRAL AND MARGINAL POPULATIONS OF DROSOPHILA SUBOBSCURA
Authors: Sperlich Diether , Feuerbach-Mravlag Heide , Lange Peter , Michaelidis Apostolos , Pentzos-Daponte Athena 
Published: April 2021

ABSTRACT
Relative viabilities of individuals homozygous or randomly heterozygous for wild O chromosomes derived from a marginal (Norwegian) and a central (Greek) population of D. subobscura were obtained by means of a newly prepared marker strain. In the central and marginal populations 20.8 and 28.8 percent of all chromosomes proved lethal or semilethal in homozygous condition. Mean viability was higher for +/+ random heterozygotes than for +/+ homozygotes. This remained the case for the marginal, but not for the central populations, after exclusion of the detrimental chromosomes from the calculations. The variances of viabilities were higher for homozygotes than for heterozygotes, but the test crosses with chromosomes from the marginal population had generally higher variances than those with chromosomes from the central population. No correlation was found in either populations between the action of a chromosome in homozygous condition with its action in heterozygous condition. This is interpreted as complete recessiveness of genetic load. The results are discussed in terms of the observed reduction of the inversion polymorphism which is not paralleled by a reduction in enzyme and, as shown here, by reduction in viability variation. It is thought that the heterotic effect of inversions is due to their homeostatic action, which depends less on structural genes than on higher orders of organization due to gene interaction or regulation. Whatever the causes, it is very likely that marginal populations differ from central populations with respect to their genetic system.
ESTIMATES OF GENETIC PARAMETERS OF BODY WEIGHT IN DESCENDANTS OF X-IRRADIATED RAT SPERMATOGONIA
Authors: Gianola Daniel , Chapman A B , Rutledge J J 
Published: April 2021

ABSTRACT
Effects of nine generations of 450r per generation of ancestral spermatogonial X irradiation of inbred rats on genetic parameters of body weight at 3, 6 and 10 weeks of age and of weight gains between these periods were studied. Covariances among relatives were estimated by mixed model and regression techniques in randomly selected lines with (R) and without (C) radiation history. Analyses of the data were based on five linear genetic models combining additive direct, additive indirect (maternal), dominance and environmental effects. Parameters in these models were estimated by generalized least-squares. A model including direct and indirect genetic effects fit more closely to the data in both R and C lines. Overdominance of induced mutations did not seem to be present. Ancestral irradiation increased maternal additive genetic variances of body weights and gains but not direct genetic variances. Theoretically, due to a negative direct-maternal genetic correlation, within full-sib family selection would be ineffective in increasing body weight at six weeks in both R and C lines. However, progress from mass selection would be expected to be faster in the R lines.
EVALUATION OF THE STEPWISE MUTATION MODEL OF ELECTROPHORETIC MOBILITY: COMPARISON OF THE GEL SIEVING BEHAVIOR OF ALLELES AT THE ESTERASE-5 LOCUS OF DROSOPHILA PSEUDOOBSCURA
Authors: Johnson George B 
Published: April 2021

ABSTRACT
Seven alleles at the esterase-5 locus of Drosophila pseudoobscura appear approximately uniformly spaced on 5% acrylamide gels. Such stepwise "ladders" in mobility have been used to argue for the charge-state model of electrophoretic mobility. To evaluate this interpretation, flies of the seven strains were examined in replicate electrophoresis on polyacrylamide gels of differing pore size, permitting estimation of the relative contributions of charge and of size/conformation to electrophoretic mobility. Six of the seven strains examined proved to be heterogeneous, containing multiple variants that migrate to similar positions on 5% acrylamide gels. In the one strain genetically analyzed to date, the hidden variants segregate in crosses. A total of fourteen variants are detected by this gel sieving analysis, many of them involving apparent conformational differences. Thus, protein properties in addition to net charge appear to play an important role in determining the degree of mobility difference between alleles. Examining estimates of free mobility, uniform charge differences are the rule within conformational classes. However, the superposition of conformational heterogeneity renders interpretation of mobility spacing solely in terms of such charge differences inappropriate.
THE POPULATION BIOLOGY OF BACTERIAL PLASMIDS: A PRIORI CONDITIONS FOR THE EXISTENCE OF CONJUGATIONALLY TRANSMITTED FACTORS
Authors: Stewart Frank M , Levin Bruce R 
Published: April 2021

ABSTRACT
A mathematical model for the population dynamics of conjugationally transmitted plasmids in bacterial populations is presented and its properties analyzed. Consideration is given to nonbacteriocinogenic factors that are incapable of incorporation into the chromosome of their host cells, and to bacterial populations maintained in either continuous (chemostat) or discrete (serial transfer) culture. The conditions for the establishment and maintenance of these infectious extrachromosomal elements and equilibrium frequencies of cells carrying them are presented for different values of the biological parameters: population growth functions, conjugational transfer and segregation rate constants. With these parameters in a biologically realistic range, the theory predicts a broad set of physical conditions, resource concentrations and dilution rates, where conjugationally transmitted plasmids can become established and where cells carrying them will maintain high frequencies in bacterial populations. This can occur even when plasmid-bearing cells are much less fit (i.e., have substantially lower growth rates) than cells free of these factors. The implications of these results and the reality and limitations of the model are discussed and the values of its parameters in natural populations speculated upon.
ELECTROPHORETIC VARIATION FOR X-CHROMOSOME-LINKED PHOSPHOGLYCERATE KINASE (PGK-1) IN THE MOUSE
Authors: Nielsen J T , Chapman V M 
Published: April 2021

ABSTRACT
Electrophoretic variation for X-chromosome-linked phosphoglycerate kinase (PGK-1) has been found as a polymorphism in feral mice in Denmark. Males from feral sampling or from a variety of genetic crosses have only a single-banded phenotype of the variant PGK-1A type or of the PGK-1B type commonly found among inbred mice. By contrast, three phenotypes were observed among females; two homozygous single-banded types and a heterozygous double-banded type. The X-chromosome linkage of the Pgk-1 locus was determined from the mode of inheritance in F1 and backcross generations and confirmed by the linkage of Pgk-1 and the X-linked markers Hq, Ta and Mo. Pgk-1 showed 29/122 recombinations with Hq, 5/185 with Ta and 0/108 recombinants with Mo. Based on these recombination data, a gene order of Hq—Ta—Pgk-1—Mo is suggested.
GENETIC MAPPING IN SCHIZOSACCHAROMYCES POMBE BY MITOTIC AND MEIOTIC ANALYSIS AND INDUCED HAPLOIDIZATION
Authors: Kohli Jürg , Hottinger Herbert , Munz Peter , Strauss Andre , Thuriaux Pierre 
Published: April 2021

ABSTRACT
The genetic maps of the fission yeast Schizosaccharomyces pombe were extended through the use of haploidization (spontaneous or induced by m-fluorophenylalanine), as well as by tetrad, random spore and mitotic analysis. A new diploidization method utilizing a meiosis-deficient mutant and improved haploidization techniques was employed. As a result of these and previous studies, 118 genetic markers have been assigned to 3 linkage groups. Centromere markers for all 3 chromosomes were identified and genetic maps containing a total of 71 genes were constructed. Our experiments indicate that 3 is very likely to be the haploid chromosome number of S. pombe.
AN EXPERIMENTAL INVESTIGATION OF THE UNIT CHARGE MODEL OF PROTEIN POLYMORPHISM AND ITS RELATION TO THE ESTERASE-5 LOCUS OF DROSOPHILA PSEUDOOBSCURA, DROSOPHILA PERSIMILIS, AND DROSOPHILA MIRANDA
Authors: Cobbs Gary , Prakash Satya 
Published: April 2021

ABSTRACT
The relationship between charge changes and electrophoretic mobility changes is investigated experimentally. The charge of several proteins is altered by reaction with small molecules of known structure and the change in electrophoretic mobility is measured. The method of Ferguson plots is used to separate charge and shape components of mobility differences. The average effect of an amino acid charge change on the mobility of the esterase-51.00 allele of Drosophila pseudoobscura is estimated to be 0.046. This estimate is then used to apply the step model of Ohta and Kimura (1973) to electrophoretic mobility data for the esterase-5 locus of D. pseudoobscura and D. miranda. The variation in electrophoretic mobility at this locus was found to be in agreement with the predictions of the step model.
FITNESS EFFECTS OF EMS-INDUCED MUTATIONS ON THE X CHROMOSOME OF DROSOPHILA MELANOGASTER. I. VIABILITY EFFECTS AND HETEROZYGOUS FITNESS EFFECTS
Authors: Mitchell Joyce A 
Published: April 2021

ABSTRACT
Drosophila melanogaster X chromosomes were mutagenized by feeding males sucrose solutions containing ethyl methanesulfonate (EMS); the concentrations of EMS in the food were 2.5 mm, 5.0 mm, and 10.0 mm. Chromosomes were exposed to the mutagen up to three times by treating males in succeeding generations. After treatment, the effective exposures were 2.5, 5.0, 7.5, 10.0, 15.0, and 30.0 mm EMS. X chromosomes treated in this manner were tested for effects on fitness in both hemizygous and heterozygous conditions, and for effects on viability in hemizygous and homozygous conditions. In addition, untreated X chromosomes were available for study. The viability and heterozygous fitness effects are presented in this paper, and the hemizygous fitness effects are discussed in the accompanying one (Mitchell and Simmons 1977). Hemizygous and homozygous viability effects were measured by segregation tests in vial cultures. For hemizygous males, viability was reduced 0.5 percent per mm EMS treatment; for homozygous females, it was reduced 0.7 percent per mm treatment. The decline in viability appeared to be a linear function of EMS dose. The viabilities of males and females were strongly correlated. Heterozygous fitness effects were measured by monitoring changes in the frequencies of treated and untreated X chromosomes in discrete generation populations which, through the use of an X-Y translocation, maintained them only in heterozygous condition. Flies that were heterozygous for a treated chromosome were found to be 0.4 percent less fit per m m EMS than flies heterozygous for an untreated one.
GLYCOLYSIS MUTANTS IN SACCHAROMYCES CEREVISIAE
Authors: Clifton Drago , Weinstock Shelley B , Fraenkel Dan G 
Published: April 2021

ABSTRACT
Mutants have been isolated in S. cereuisiae with the phenotype of growth on pyruvate but not on glucose, or growth on rich medium with pyruvate but inhibition by glucose. Screening of mutagenized cultures was either without an enrichment step, or after enrichment using the antibiotic netropsin (YOUNG et al. 1976) or inositol starvation (HENRY, DONAHUEand CULBERTSON 1975). One class of mutants lacked pyruvate kinase (p y k), another class had all the enzymes of glycolysis, and one mutant lacked phosphoglucose isomerase (pgi, MAITRA 1971). Partial reversion of pyruvate kinase mutants on rich medium containing glucose gave double mutants now'also lacking hexokinase (hzk), phosphofructokinase (pfk), or several enzymes of glycolysis (gcr) . In diploids the mutations were recessive. pyk, pgi, pfk, and gcr segregated 2:2 from their wild-type alleles. PYK hxk, PYK pfk, and PYK gcr segregants grew on glucose.
VARIANCE COMPONENT ANALYSIS OF ALLOZYME FREQUENCY DATA FROM EASTERN POPULATIONS OF DROSOPHILA MELANOGASTER
Authors: Smith Diana B , Langley Charles H , Johnson Frank M 
Published: April 2021

ABSTRACT
Gene frequency variation at eight polymorphic allozyme loci in Drosophila meianogaster populations in North Carolina and the east coast of the United States were analyzed utilizing the variance component estimation procedures suggested by COCKERHAM (1969, 1973). These variance components were used to estimate correlations of genes within small geographic regions. The average (over loci) correlation between genes in the same individual within subpopulations was estimated to be 0.033. That between genes in the same subpopulation in different individuals was estimated to be very small, although significantly different from zero. The macrogeographic variation measured by the correlation of genes sampled from the same local region was large for some loci and smaller for others. This variation was also analyzed by correlation with latitude and longitude. Several previously recognized clines were identified as were several new clines.—These results were interpreted as indicating either some degree of nonrandom mating and locel breeding unit isolation or a low frequency of null alleles. The geographic and temporal variation has no simple interpretation.
ISOLATION AND CHARACTERIZATION OF PERITHECIAL DEVELOPMENT MUTANTS IN NEUROSPORA
Authors: Johnson Thomas E 
Published: April 2021

ABSTRACT
The isolation and characterization of mutants that block perithecial development in Neurospora crassa are described. Several classes of mutants have been isolated after UV mutagenesis, and those that block perithecial development when used as the female (protoperithecial) component of a cross have been further characterized. These mutants fall into 29 complementation groups. Twelve of the 33 mutants block development at the protoperithecial stage; no other clustering of block points is observed. Many of the mutants show an altered vegetative growth rate as well; in several mutants this lower growth rate cosegregates with the female sterile phenotype. Only one mutant also blocks development of the perithecium when used as the conidial parent. None of the mutants are temperature sensitive; two can be suppressed by growth on a complete crossing medium. There is no indication that the mutants are at or in the mating-type locus, nor are any of the mutants mating-type specific. Genetic mosaics have been formed using mixtures of mutant and marked wild-type nuclei; no mutants are cell autonomous by this criterion. The significance of these results in terms of "developmental" mutants isolated in other organisms and in relation to models of eukaryotic development is discussed.
CROSSOVER SUPPRESSORS AND BALANCED RECESSIVE LETHALS IN CAENORHABDITIS ELEGANS
Authors: Herman Robert K 
Published: April 2021

ABSTRACT
Two dominant suppressors of crossing over have been identified following X-ray treatment of the small nematode C. elegans. They suppress crossing over in linkage group II (LGII) about 100-fold and 50-fold and are both tightly linked to LGII markers. One, called C1, segregates independently of all other linkage groups and is homozygous fertile. The other is a translocation involving LGII and X. The translocation also suppresses rrossing over along the right half of X and is homozygous lethal. CI has been used as a balancer of LGII recessive lethal and sterile mutations induced by EMS. The frequencies of occurrence of lethals and steriles were approximately equal. Fourteen mutations were assigned to complementation groups and mapped. They tended to map in the same region where LGII visibles are clustered.
SELECTION OF SALMONELLA TYPHIMURIUM MUTANTS WITH ALTERED SERINE TRANSHYDROXYMETHYLASE REGULATION
Authors: Stauffer George V , Brenchley Jean E 
Published: April 2021

ABSTRACT
In Salmonella typhimurium the glyA gene product, serine transhydroxymethylase (E.C. 2.1.2.1; L-serine:tetrahydrofolate-5,10-hydroxymethyltransferase) is responsible for the interconversion of serine and glycine. This reaction also provides the cell with one-carbon units from the 5,10-methylenetetrahydrofolate formed during glycine synthesis. Despite the importance of this enzyme, however, no mutants in which its regulation has been specificially altered have been isolated. To isolate such mutants, we have devised a selection procedure using a strain (glyA951) in which the serine transhydroxymethylase activity is reduced. When this enzyme is completely repressed, the mutant requires glycine for growth. Revertants which retain the glyA951 lesion, but no longer require glycine, have been isolated and the serine transhydroxymethylase regulation examined. One revertant has a 7-fold elevated serine transhydroxymethylase level, which can be repressed the normal amount (about 5-fold) when the cells are grown in supplemented media. Another revertant has only a 2-fold higher serine transhydroxymethylase level; however, the amount of repression is reduced. The new lesions in both mutants cotransduce with the glyA gene and are distinct from other mutations that alter the regulation of both serine transhydroxymethylase and the methionine biosynthetic enzymes.