bluuebunny/crossref_metadata_2025_split huggingface dataset:
STABILIZING SELECTION FOR PUPA WEIGHT IN TRIBOLIUM CASTANEUM
Authors: Kaufman Pamela K , Enfield Franklin D , Comstock Ralph E 
Published: April 2021

ABSTRACT
Ninety-five generations of stabilizing selection for pupa weight in Tribolium castaneum resulted in a significant decrease in phenotypic variance, moderate reductions in additive genetic variance, but only slight changes in heritability for the trait. Sterility was significantly lower and the average number of live progeny per fertile mating was significantly higher in populations where stabilizing selection was practiced as compared with random selected populations. The results indicate that more genetic variability is being maintained than would be expected unless a fraction of the genes have a heterozygote advantage on the fitness scale. The reduction in phenotypic variance indicated that the populations with stablizing selection became somewhat more buffered against environmental sources of variation over the course of the experiment.
SPONTANEOUS AND ETHYL METHANESULFONATE-INDUCED MUTATIONS CONTROLLING VIABILITY IN DROSOPHILA MELANOGASTER. I. RECESSIVE LETHAL MUTATIONS
Authors: Ohnishi Ohmi 
Published: April 2021

ABSTRACT
The efficiency of the adult feeding method for EMS treatment in Drosophila melanogaster was studied by measuring the frequency of induced recessive lethals on the second chromosome. The treatment was most effective when mature spermatozoa or spermatids were treated and was much less effective on earlier stages. The number of mutations induced was proportional to the concentration except at the highest doses. The recessive lethal rate was estimated to be about 0.012 per second chromosome per 10-4m. In addition, about 0.004-0.005 recessive lethals per 10-4 m were found in a later generation in chromosomes that had not shown the lethal effect in the previous generation. When the experiments are done in a consistent manner and gametes treated as mature sperm or spermatids are sampled, the results are highly reproducible. However, modifications of the procedure, such as starvation before EMS treatment, can considerably alter the effectiveness of the mutagen.
ESTIMATION OF FITNESS COMPONENTS IN DROSOPHILA MELANOGASTER. I. HETEROZYGOTE VIABILITY INDICES
Authors: Katz Alan J , Cardellino Ricardo A 
Published: April 2021

ABSTRACT
We examine the assumption of "dominance" with regard to viability of the Cy and Pm marker chromosomes in D. melanogaster. This assumption is often invoked for the extraction of wild-type second chromosomes from natural populations and for the calculation of relative viability indices. Significant genotypic variances for viability are found among both C y / f i and P m / f i heterozygotes in California and Japanese populations. The magnitude of the Pm/+i genotypic variance is substantially less than that of the Cy/+j heterozygotes (less than one half). Significant reciprocal effects are also found to influence Cy/+j, Pm/+i and + J f j viabilities. We conclude that viability indices of heterozygotes based on the Curly method are biased. We suggest that viability indices in the future be expressed relative to the viability of the Cy/Pm genotype (Curly-Plum method) or possibly that of the Pm/+i genotype (Plum method).
THE PRODUCTION OF CHROMOSOME ABERRATIONS IN VARIOUS MAMMALIAN CELLS BY TRIETHYLENEMELAMINE
Authors: Luippold H E , Gooch P C , Brewen J G 
Published: April 2021

ABSTRACT
The cytogenetic effects of triethylenemelamine (TEM) were studied using five different mammalian tissues. Treatments of 0.1 and 0.2 mg/kg TEM on differentiating mouse spermatogonia and bone marrow cells showed no significant differences in the frequency of chromosomal aberrations produced in these two tissues. At higher doses, however, the sensitivities of the two tissues appear to be different. The frequency of aberrations varies with time after treatment, with the greatest amount occurring at the later fixation times. Results of an experiment on primary spermatocytes indicated a correlation between the frequency of chromosome aberrations and DNA replication. Human peripheral leukocytes were utilized in an attempt to clarify the cellstage specificity of TEM-induced chromosome aberrations. Cultures were treated with TEM prior to PHA stimulation (G0), as well as various time intervals after stimulation (late G,1 S, and G2). The most sensitive stages of the cell cycle to aberration induction were later G1 and S, with chromatid aberrations the predominant type. A very low yield of chromosome damage was observed with the G0 and G1 treated stages. The experiments described tend to support the view that TEM is most effective at inducing aberrations when an intervening round of DNA replication has occurred.
A CHROMOSOMAL TRANSLOCATION CAUSING OVERPRODUCTION OF ISO-2-CYTOCHROME c IN YEAST
Authors: Sherman Fred , Helms Cynthia 
Published: April 2021

ABSTRACT
The CYC7-1 mutation in the yeast Saccharomyces cerevisiae causes the production of approximately 30 times the normal amount of iso-2-cytochrome c. Genetic analysis established that the CYC7-1 mutation is a reciprocal translocation involving the left arm of chromosome V and the right arm of chromosome XVI. The chromosome V arm was broken adjacent to the gene CYC7, which determines the primary structure of iso-2-cytochrome c, and this fragment containing the CYC7 gene was joined to the segment of chromosome XVI. It appears as though the elevation of iso-2-cytochrome c is caused by an abnormal controlling region adjacent to the structural region of the CYC7 gene.
A FINE-STRUCTURE GYNANDROMORPH FATE MAP OF THE DROSOPHILA HEAD
Authors: Baker William K 
Published: April 2021

ABSTRACT
A gynandromorph fate map of the head of D. melanogaster was produced using 28 landmarks derived from one imaginal disc. An examination of the meaning of fine-structure mapping discloses that the sturt value observed between one pair of landmarks within a disc may approximate the relative physical distance of their progenitor cells at blastoderm, but for another pair of landmarks (assuming no directed cell movements), the sturt value may simply reflect their close geographic location at the time the cells are specified for their particular differentiation, a time much later in development when most cell division within the disc has come to an end. The formation of early developmental compartments has little effect on fate-map distances. Our analysis of the data suggests there are approximately ten cells present at the blastoderm stage that are head progenitors. Each blastoderm cell is likely to be the progenitor of a particular array of landmarks, but there is overlap between arrays from different blastoderm cells.
CLINES WITH ASYMMETRIC MIGRATION
Authors: Nagylaki Thomas 
Published: April 2021

ABSTRACT
The consequences of asymmetric dispersion on the maintenance of an allele in a one-dimensional environmental pocket are examined. The diffusion model of migration and selection is restricted to a single diallelic locus in a monoecious population in the absence of mutation and random drift. It is further supposed that migration is homogeneous and independent of genotype, the population density is constant and uniform, and Hardy-Weinberg proportions obtain locally. If dispersion is preferentially out of an environmental pocket at the end of a very long habitat, the condition for maintaining the allele favored in the pocket becomes less stringent than for symmetric migration; dispersion preferentially into the pocket increases the severity of the condition for polymorphism. If an allele is harmful in large regions on both sides of an environmental pocket, the probability for polymorphism is decreased by asymmetric migration. The criterion for the existence of a cline is independent of the sense of the asymmetry; the cline itself is not. These phenomena are studied both analytically and numerically.—It is shown for symmetric migration and variable population density that the more densely populated parts of the habitat are more influential in determining gene frequency than the others. Thus, the higher the population density in an environmental pocket, the more easily an allele beneficial in the pocket will be maintained in the population.
GENETIC INSTABILITY IN AUXOTROPHS OF SALMONELLA TYPHIMURIUM REQUIRING CYSTEINE OR METHIONINE AND RESISTANT TO INHIBITION BY 1,2,4-TRIAZOLE
Authors: Kingsman A J , Smith D A , Hulanicka M D 
Published: April 2021

ABSTRACT
Triazole-resistant (Trzr) derivatives of six cysteine- or methionine-requiring (Cym-) mutants of Salmonella typhimurium were isolated. Some of the derivatives of each mutant (CTS) were prototrophic, i.e., Cym- was suppressed. In every case suppression was initially unstable, Cym- auxotrophs being segregated at high frequency, although Trzr was stable. After several subcultures on selective medium, CTS strains were classified as either persistently unstable or stabilized. The unstable strains segregated Cym- auxotrophs at frequencies of 50-70%, whereas the stabilized strains segregated at frequencies of less than 1%. All suppressed strains had a stable Trzr marker co-transducible with cysA. However, there was a correlation between the class of CTS strain and Cym- phenotype. The stabilized strains were Cym+, whereas the unstable strains were Cym-. Acriflavin and ethidium bromide increased segregation in the unstable strains, suggesting the involvement of a plasmid. The stabilized strains were refractory to the curing agents. There was no detectable change in the quantity or quality of the S. typhimurium cryptic plasmid. The Trzr phenotype of the CTS strains suggested that Trzr mutations were of the stable TrzA type. It is suggested that correction of the Cym- lesions in CTS strains results from an insertion within the cysCDHIJ gene cluster of a DNA species originating in the cysALKptsHI region of the S. typhimurium chromosome.
THE NATURE OF GENETIC INSTABILITY IN AUXOTROPHS OF SALMONELLA TYPHIMURIUM REQUIRING CYSTEINE OR METHIONINE AND RESISTANT TO INHIBITION BY 1,2,4-TRIAZOLE
Authors: Kingsman A J , Smith D A 
Published: April 2021

ABSTRACT
We tested the hypothesis that unstable suppression of auxotrophy in triazole-resistant derivatives of Cym- mutants of Salmonella typhimurium is due to reversible insertion at the Cym- site of genetic material originating in the cysALKptsHI region. We have shown that the unstable phenotype was co-transducible with markers in the cysCDHIJ region. The suppression of the Cym phenotype was recA dependent and frequencies of segregation were affected by UV irradiation. Restored enzyme activity in suppressed strains was determined by wild-type enzyme, suggesting that the unstable regions are located in cys gene regulatory regions. These results support the hypothesis. In contradiction, we found no evidence for a deletion in the cysALKptsHI region.
INDUCED RESISTANCE TO 6-METHYLPURINE AND CYCLOHEXIMIDE IN TETRAHYMENA. I. GERM LINE MUTANTS OF T. THERMOPHILA
Authors: Byrne Bruce C , Brussard Trudy B , Bruns Peter J 
Published: April 2021

ABSTRACT
Two new mutant lines of Tetrahymena thermophila (T. pyriformis, syngen 1), each conferring resistance to a different agent, are described. Resistance to cycloheximide and 6-methylpurine are each determined by dominant genes, ChxA2 and Mpr; the traits show phenotypic assortment. The method used to select these mutations, the critical importance of backcrossing to wild type following mutagenesis, and the utility of these marker genes in further mutagenic selection schemes and studies of the sexual cycle of Tetrahymena are noted.
INTRAGENIC SUPPRESSION AT THE b2 LOCUS IN ASCOBOLUS IMMERSUS. I. IDENTIFICATION OF THREE DISTINCT GROUPS OF SUPPRESSION
Authors: Leblon G , Paquette N 
Published: April 2021

ABSTRACT
A reversion study of EMS- or ICR170-induced ascospore color mutants in Ascobolus immersus is reported. Twenty-three new intragenic suppressors were isolated within the b2 locus. These are localized within three distinct groups on a genetic fine-structure map containing 21 identifiable sites. The pattern of reversion is discussed according to the known specificity of EMS and ICR170 in Ascobolus immersus.
NOVEL INTERALLELIC COMPLEMENTATION AT THE his1 LOCUS OF YEAST
Authors: Lax Carol , Fogel Seymour 
Published: April 2021

ABSTRACT
In yeast, 17 histidine-requiring mutants derived from and interallelically complementary to his1—7 were analyzed. The genetic basis of the complementation response was elucidated by mitotic and meiotic gene conversion. Each allele probably carries an unaltered 7-site mutation and a unique second-site alteration. The second-site alterations appear to be clustered within the proximal and distal segments of the his1 structural gene. Models of intraallelic complementation are reviewed in light of the unique complementational response between a single-site mutant and a double mutant including the identical altered base sequence.
THE ISLAND MODEL WITH STOCHASTIC MIGRATION
Authors: Nagylaki Thomas 
Published: April 2021

ABSTRACT
The island model with stochastically variable migration rate and immigrant gene frequency is investigated. It is supposed that the migration rate and the immigrant gene frequency are independent of each other in each generation, and each of them is independently and identically distributed in every generation. The treatment is confined to a single diallelic locus without mutation. If the diploid population is infinite, selection is absent and the immigrant gene frequency is fixed, then the gene frequency on the island converges to the immigrant frequency, and the logarithm of the absolute value of its deviation from it is asymptotically normally distributed. Assuming only neutrality, the evolution of the exact mean and variance of the gene frequency are derived for an island with finite population. Selection is included in the diffusion approximation: if all evolutionary forces have comparable roles, the gene frequency will be normally distributed at all times. All results in the paper are completely explicit.
LOCALIZED MUTAGENESIS FOR THE ISOLATION OF TEMPERATURE-SENSITIVE MUTANTS OF ESCHERICHIA COLI AFFECTED IN PROTEIN SYNTHESIS
Authors: Champney W Scott 
Published: April 2021

ABSTRACT
Two variations of the method of localized mutagenesis were used to introduce mutations into the 72 min region of the Escherichia coli chromosome. Twenty temperature-sensitive mutants, with linkage to markers in this region, have been examined. Each strain showed an inhibition of growth in liquid medium at 44°, and 19 of the mutants lost viability upon prolonged incubation at this temperature. A reduction in the rate of in vivo RNA and protein synthesis was observed for each mutant at 44°, relative to a control strain. Eleven of the mutants were altered in growth sensitivity or resistance to one or more of three ribosomal antibiotics. The incomplete assembly of ribosomal subunits was detected in nine strains grown at 44°. The characteristics of these mutants suggest that many of them are altered in genes for translational or transcriptional components, consistent with the clustering of these genes at this chromosomal locus.
INTERALLELIC COMPLEMENTATION AT THE sh LOCUS IN MAIZE AT THE ENZYME LEVEL
Authors: Chourey Prem S , Nelson Oliver E 
Published: April 2021

ABSTRACT
EMS-induced sh mutants and their heterozygotes were examined for the enzyme, sucrose synthetase, which has previously been shown to be coded by the Sh locus. Complementing heterozygotes have a wild-type phenotype, but show no hybrid protein band after starch gel electrophoresis. The existence of a heteromeric complex, however, is inferred from the two-fold elevation in sucrose cleavage activity in the complementing heterozygotes as compared to the mutant homozygotes. The observations on complementation described here are unique, as the elevation in the activity of this reversible enzyme is noticed only in one direction (viz, sucrose cleavage) of the reaction and not the other (sucrose synthesis).
FINE-STRUCTURE MAPPING OF THE ACETAMIDASE STRUCTURAL GENE AND ITS CONTROLLING REGION IN ASPERGILLUS NIDULANS
Authors: Hynes M J 
Published: April 2021

ABSTRACT
A large number of amdS mutants altered in acetamide utilization have been used to construct a fine-structure map of the amdS locus. The mutagen diepoxyoctane generated most of the deletion strains used for mapping. A minimum of 14 sites within the amdS gene were found. Biochemical analysis of amds mutants defined the extent of the probable coding region. A new mutant, amd-205, which did not produce detectable inactive gene product, was found to be inseparable by recombination from the "up-promoter" mutation amdl8 and was located outside of the apparent amdS coding region. The cis dominant mutation, amdI9, was also located at this end of the gene. This work, therefore, provides evidence for the separation of a eukaryotic gene into controlling and structural regions.
A GENETICALLY DISTINCT FORM OF CYCLIC AMP PHOSPHODIESTERASE ASSOCIATED WITH CHROMOMERE 3D4 IN DROSOPHILA MELANOGASTER
Authors: Kiger John A , Golanty Eric 
Published: April 2021

ABSTRACT
Two cyclic AMP phosphodiesterase enzymes (E.C.3.1.4.17) are present in homogenates of adult Drosophila melanogaster. The two enzymes differ from one another in heat stability, affinity for Mg++, Ca++ activation and molecular weight. They do not differ markedly in their affinities for cyclic AMP, and both exhibit anomalous Michaelis-Menten kinetics. The more heatlabile enzyme is controlled in a dosage-dependent manner by chromomere 3D4 of the X chromosome and is absent in flies that are deficient for chromomere 3D4. Chromomere 3D4 is also necessary for the maintenance of normal cAMP levels, for male fertility, and for normal female fertility and oogenesis. The structural gene(s) for the more heat-stable enzyme is located outside of chromomeres 3C12-3D4. Whether 3D4 contains a structural gene, or a regulatory gene necessary for the presence of the labile enzyme, remains to be determined.
THE GENETICS OF COPPER TOLERANCE IN THE YELLOW MONKEY FLOWER, MIMULUS GUTTATUS. I. CROSSES TO NONTOLERANTS
Authors: Macnair Mark R 
Published: April 2021

ABSTRACT
The biometrical genetics of copper tolerance has been investigated in two Californian populations of Mimulus guttatus by crosses to a nontolerant British population. A simple biometrical model involving only additive and dominance effects is not sufficient. When the first order interactions are included, the model is shown to fit the data. Interactions between the dominance effects of different loci, and between dominance and additive effects, are the most important. These interactions can be explained either by a threshold model, or by postulating dominance modification.
AN EXTENSION OF A MODEL FOR THE EVOLUTION OF MULTIGENE FAMILIES BY UNEQUAL CROSSING OVER
Authors: Ohta Tomoko 
Published: April 2021

ABSTRACT
Evolution of a multigene family is studied from the standpoint of population genetics. It is assumed that the multigene family is undergoing continuous interchromosomal unequal crossing over, mutation and random frequency drift. The equilibrium properties of the probability of gene identity (clonality) are investigated, using two measures: identity probability within and between chromosomes. The measures represent homogeneity of genes within a family in one chromosome and $milarity of gene families between two homologous chromosomes. The means, the variances and the covariance of these two measures of identity probability are obtained by using the diffusion equation method. It is shown that the means and the variances are generally smaller than those predicted in the previous model assuming intrachromosomal (sister chromatid) unequal crossing over (OHTA 1978a,b).
A MUTANT KILLER PLASMID WHOSE REPLICATION DEPENDS ON A CHROMOSOMAL "SUPERKILLER" MUTATION
Authors: Toh-E Akio , Wickner Reed B 
Published: April 2021

ABSTRACT
Yeast strains carrying a 1.5 × 106 molecular weight linear double-stranded RNA in virus-like particles (M dsRKA, the killer plasmid or virus) secrete a toxin that is lethal to strains not carrying this plasmid. Recessive mutations in any of four chromosomal genes (called skil-ski4) result in increased production of toxin activity. We report here a mutation of the killer plasmid (called [KIL-sd] for ski-dependent) that makes the killer plasmid dependent for its replication on the presence of a chromosomal mutation in any ski gene. Thus, the [KIL-sd] plasmid is lost from SKI+ strains. When the wild-type killer plasmid, [KIL-k], is introduced into a ski2-2 [KIL-o] strain, the killer plasmid changes to a [KIL-sd] plasmid. This may represent a specific form of mutagenesis or selective replication in the ski2-2 strain of [KIL-sd] variants (mutants) in the normal [KIL-k] population. The ski2-1 and ski2-3 mutations do not convert [KIL-k] to [KIL-sd], but ski2-3 does allow maintenance of the [KIL-sd] plasmid. The [KIL-sd] plasmid thus lacks a plasmid site or product needed for replication in wild-type cells.
POST-TRANSLATIONAL MODIFICATION AS A POTENTIAL EXPLANATION OF HIGH LEVELS OF ENZYME POLYMORPHISM: XANTHINE DEHYDROGENASE AND ALDEHYDE OXIDASE IN DROSOPHILA MELANOGASTER
Authors: Finnerty Victoria , Johnson George 
Published: April 2021

ABSTRACT
Xanthine dehydrogenase (XDH) and aldehyde oxidase (AO) in Drosophila melanogaster require for their activity the action of another unlinked locus, maroon-like (mal), While the XDH and A 0 loci are on chromosome 3, mal maps to the X chromosome. Although functional mal gene product is required for XDH and A 0 activity, it is possible to examine the effects of mutant mal alleles in those cases when pairs of mutants complement to produce a partial restoration of activity. To test whether mal mediates a post-translational modification of the XDH and A0 proteins, we constructed several mal heteroallelic complementing stocks of Drosophila in which the third chromosomes were co-isogenic. Since all lines were co-isogenic for the XDH and A0 structural genes, any variation in these enzymes seen when comparing these stocks must have been produced by post-translational modification by mal. We examined the XDH and A 0 proteins in these stocks by gel-sieving electrophoresis, a procedure that permits independent characterization of a protein's charge and shape, and is capable of discriminating many variants not detected in routine electrophoresis. In every mal heteroallelic combination, there is a significant alteration in protein shape, when compared to wild type. The magnitude of differences in shape of XDH and AO is correlated both with differences in their enzyme activities and with differences in their thermal stabilities. As the body of this variation appears heritable, any functional differences resulting from these variants are of real genetic and evolutionary interest. A similar post-translational modification of XDH and A0 by yet another locus, lxd, was subsequently documented in an analogous manner. The pattern of electrophoretic differences produced by mal and lxd modification is similar to that reported for electrophoretic "alleles" of XDH in natural populations. The implication is that heritable variation in electrophoretic mobility at these two enzyme loci, and potentially at other loci, is not necessarily allelic to the structural gene loci.