bluuebunny/crossref_metadata_2025_split huggingface dataset:
DIAMINOPURINE-RESISTANT MUTANTS OF CULTURED, DIPLOID HUMAN FIBROBLASTS
Authors: Rappaport Harriet , DeMars Robert 
Published: January 2021

ABSTRACT
Clones of cells resistant to 2,6-diaminopurine were detected in skin fibroblast cultures derived from 13 of 21 normal humans of both sexes from 17 unrelated families. Almost all of the cultures that yielded mutants were chosen for further study from among a total of 83 surveyed because they displayed a slight resistance to low concentrations of diaminopurine. The incidences of mutant colonies ranged between about 10-5 and 10-4 per cell surviving prior mutagenic treatment with MNNG. The incidences of spontaneous mutants were about 10-7 to 10-5 in three unrelated cultures. Most independent mutants had distinctly reduced activity of adenine phosphoribosyltransferase but some had apparently normal amounts of activity. Two mutants from unrelated boys had little or no detectable enzyme activity and were unable to effectively use exogenous adenine for growth when purine biosynthesis was blocked with azaserine. Most mutants could utilize exogenous adenine, just as most azaguanine-resistant fibroblast mutants can utilize exogenous hypoxanthine, even when their hypoxanthine-guanine phosphoribosyltransferase activity is reduced. Diverse genetic changes conferred diaminopurine resistance but their specific natures are still undefined. Gross numerical or structural chromosome abnormalities were not observed in the mutants examined so far. Since at least one gene responsible for adenine phosphoribosyltransferase activity is on autosome No. 16 our results suggest that at least some of the cultures yielding mutants were heterozygous and that alleles conferring d;aminopurine resistance may be frequent enough to comprise a polymorphism.
MARKER EFFECTS IN THE GENETIC TRANSDUCTION OF TRYPTOPHAN MUTANTS OF E. COLI
Authors: Stadler David , Kariya Beverly 
Published: January 2021

ABSTRACT
Recombination frequencies have been determined in crosses involving 28 mutant strains for 20 of which the site of the alteration is known from studies of amino-acid substitutions in the protein products. Three of these mutants showed especially high frequencies of recombination when crossed to other single mutants or when crossed to a strain carrying two alterations at opposite ends of the trpA gene. There is no obvious molecular explanation of the high recombination of these three mutants. They include one missense mutant, one amber and one ochre. The low-frequency recombination mutants include all these same classes as well as frameshift mutants. There is nothing unique about the intragenic location of the high-recombination mutants; in each case there is at least one low-recombination mutant in the same codon.—Crosses involving mutants which were isolated in an altered wild type have shown that the behavior of a high-recombination mutant does not result from its molecular configuration alone, but from its combination with the homologous wild-type sequence from the other parent.—Several lines of evidence indicate that recombination in this system frequently involves closely-spaced double exchanges (about 40 codons apart).
GENETIC ANALYSIS OF HYBRID STRAINS TRISOMIC FOR THE CHROMOSOME CONTAINING A FATTY ACID SYNTHETASE GENE COMPLEX (fas1) IN YEAST
Authors: Culbertson Michael R , Henry Susan A 
Published: January 2021

ABSTRACT
Evidence of spontaneous n+1 aneuploidy has been obtained by trisomic segregation analysis of four independently maintained stocks of Saccharomyces cerevisiae defective in saturated fatty acid synthesis (fas1). In all cases tested, only the chromosome bearing the mutant fatty acid locus was disomic. Tetrad analysis of trisomic hybrids enabled the identification of chromosome XI as the one bearing the fatty acid locus and the assignment of fragment 5 to chromosome XI. Statistical analysis of tetrad frequencies generated by markers in triplex configuration provided information on the meiotic configuration of pairing of the three homologous chromosomes. The possible relationship between defective nuclear membranes and the disjunction of chromosomes in fas1 strains is discussed.
NUCLEAR GENE-INDUCED PLASTOME MUTATIONS IN OENOTHERA HOOKERI. I. GENETIC ANALYSIS
Authors: Epp Melvin D 
Published: January 2021

ABSTRACT
A nuclear gene mutation in Oenothera hookeri increases the frequency of variegated sectors. The gene is recessive; the variegation is cytoplasmically transmitted. Once variegation is induced, the mutant gene is not required for its continued expression. The induced sectors may differ one from another. The gene expresses unique patterns of penetrance and of maternal effect. The genetic data implicate the chloroplasts as the site for the expression of variegation. The chloroplasts of O. parviflora are also subject to the action of the nuclear gene. Possible mechanisms by which a gene might cause chloroplasts to mutate are discussed.
ISOLATION OF CIRCADIAN CLOCK MUTANTS OF NEUROSPORA CRASSA
Authors: Feldman Jerry F , Hoyle Marian N 
Published: January 2021

ABSTRACT
Three mutants of Neurospora crassa have been isolated which have altered period lengths of their circadian rhythm of conidiation. The strains, designated "frequency" (frq), were obtained after mutagenesis of the band (bd) strain with N-methyl-N'-nitro-N-nitrosoguanidine. In continuous darkness at 25° bd has a period length of 21.6 ± 0.5 hours; under the same conditions the period length of frq-1 is 16.5 ± 0.5 hours; frq-2, 19.3 ± 0.4 hours; and frq-3, 24.0 ± 0.4 hours. Each of the mutants segregates as a single nuclear gene. All three mutants appear very tightly linked to each other, but it has not yet been determined whether the mutants are allelic. No major changes in the responses to light and temperature have been observed in any of the mutants. It is suggested that these mutants represent alterations in the basic timing mechanism of the circadian clock of Neurospora.
MOSAIC ANALYSIS OF LETHAL MUTATIONS IN DROSOPHILA
Authors: Bryant Peter J , Zornetzer Michelle 
Published: January 2021

ABSTRACT
The effects of various lethal mutations were studied when they were present in the hemizygous state as sectors in genetic mosaics (gynandromorphs) of Drosophila melanogaster. Sixty percent of the lethals studied can survive to adulthood in combination with normal tissue in mosaics, whereas the remainder cause the death of such mosaic animals. Some of the gynandromorph-viable lethals appeared to be locally active, in that they allowed the survival of only those mosaics in which the male tissue was present in the abdomen. The regions affected by these lethals were identified more precisely by analysis of the tissue distributions in the surviving gynandromorphs.
THE APPLICATION OF THE MAIZE-DERIVED GENE COMPETITION MODEL TO THE PROBLEM OF DOSAGE COMPENSATION IN DROSOPHILA
Authors: Schwartz Drew 
Published: January 2021

ABSTRACT
The gene competition model, originally formulated from studies on the regulation of alcohol dehydrogenase activity in maize, is also applicable to the phenomenon of dosage compensation in Drosophila. The model accounts for the absence of dosage compensation in sex determination.
THE EFFECTS OF DISRUPTIVE AND STABILIZING SELECTION ON BODY SIZE IN DROSOPHILA MELANOGASTER. I. MEAN VALUES AND VARIANCES
Authors: Bos M , Scharloo W 
Published: January 2021

ABSTRACT
Disruptive and stabilizing selection were applied to thorax and wing length in Drosophila melanogaster. Disruptive selection with negative assortative mating (D-) practiced on thorax length caused a large increase of the phenotypic variance; practiced on wing length the increase was less striking. Disruptive selection with random mating (DR) caused in most lines only a temporary increase in phenotypic variance, but mean values increased considerably. Stabilizing selection (S) on thorax length or wing length did not decrease the phenotypic variance, but the mean value of the selected character declined.—The proportion of flies emerging decreased in all lines, while development time increased. Variance of development time increased in the D--lines. In both D--lines the frequency of flies with an abnormal number of scutellars was high (&gt; 60% in one of the lines) and there was a temporary increase in abnormal segmentation of the abdomen.
THE EFFECTS OF DISRUPTIVE AND STABILIZING SELECTION ON BODY SIZE IN DROSOPHILA MELANOGASTER. II. ANALYSIS OF RESPONSES IN THE THORAX SELECTION LINES
Authors: Bos M , Scharloo W 
Published: January 2021

ABSTRACT
An analysis was made of changes in mean and variance in some thorax selection lines. The decrease of mean thorax length in the stabilizing selection lines (S) was a consequence of a directional selection component, caused by the skewness of the frequency distributions. The slight or temporary increase of the phenotypic variance and the large increase of the mean value in the disruptive selection lines with random mating (DR) could be attributed to differences in reproduction between small and large flies (egg production and mating success). Phenotypic variability was high in two disruptive selection lines with compulsory mating of opposite extremes (D-). The mechanism of the change in variability was different in these replicate lines. In D--1 the change was obtained by an increase of the environmental and the nonadditive genetic components of the variance. In D--2 almost exclusively an increase of additive genetic variance occurred.
GENE FLOW AND SELECTION IN A CLINE
Authors: Slatkin Montgomery 
Published: January 2021

ABSTRACT
A model of the effect of gene flow and natural selection in a continuously distributed, infinite population is developed. Different patterns of spatial variation in selective pressures are considered, including a step change in the environment, a "pocket" in the environment and a periodically varying environment. Also, the problem of the effect of a geographic barrier to dispersal is analyzed. The results are: (1) there is a characteristic length scale of variation of gene frequencies, (see PDF). The population cannot respond to changes in environmental conditions which occur over a distance less than the characteristic length. The result does not depend either on the pattern of variation in selective pressures or on the exact shape of the dispersal function. (2) The reduction in the fitness of the heterozygote causes a cline in gene frequencies to become steeper. (3) A geographic barrier to dispersal causes a drastic change in the gene frequencies at the barrier only when almost all of the individuals trying to cross the barrier are stopped.
GENETICS OF HEADING TIME IN WHEAT (TRITICUM AESTIVUM L.). II. THE INHERITANCE OF VERNALIZATION RESPONSE
Authors: Klaimi Y Y , Qualset C O 
Published: January 2021

ABSTRACT
The inheritance of vernalization response was studied in crosses involving four spring wheats (Sonora 64 (S), Pitic 62 (P), Justin (J) and Thatcher (T)) and three winter wheats (Blackhull (B), Early Blackhull (E) and Extra Early Blackhull (EE)).—All winter cultivars were highly responsive to vernalization, and Pitic 62 was the only spring cultivar whose time to heading was significantly accelerated following cold treatments. When vernalized and grown under long days, spring and winter cultivars became comparable in their heading response, indicating that cold requirement is the major attribute differentiating the heading behavior of true spring and true winter wheats.—Inheritance of growth habit in the F1 generation of a five-parent diallel cross showed dominance of the spring character in all spring × winter crosses. Depending on the cross, one or two duplicate major genes governing growth habit were detected in F2, F3 and backcross generations grown in the field under long days in the absence of vernalizing temperatures. In some spring × winter crosses most of the variation in heading time among spring segregates could be attributed to the effects of major genes conditioning growth habit. In other crosses the heading patterns appeared more complex, indicating that genes with smaller effects are also involved in the control of heading response under spring or summer environments.—Evidence was presented supporting the hypothesis that the cultivar Pitic 62 carries a different allele at one of the two major loci governing its spring habit. This allele was associated with some response to vernalization and acted as a dominant gene determining earliness under low temperature vernalization, but as a partially recessive gene determining lateness in the absence of vernalizing temperatures. Genotypes were assigned to five cultivars as follows: S, CC DD; P, CC D'D'; J, cc DD; B and EE, cc dd.—The presence of major and minor genes and of multiple alleles governing response to photoperiod and vernalization was discussed in relation to the genetic manipulation of the heading response and to breeding wheat cultivars with specific or broad adaptation.
INTERACTION BETWEEN NATURAL SELECTION FOR HETEROZYGOTES AND DIRECTIONAL SELECTION
Authors: Verghese Margrith Wehrli 
Published: January 2021

ABSTRACT
When directional selection for an additively inherited trait is opposed by natural selection favoring heterozygous genotypes a selection plateau may be reached where genetic variance is present. The amount of response when this plateau is reached is a simple function of the selection response in the first generation and the intensity of natural selection. When selection is practiced in small populations, the sizes of the initial equilibrium gene frequencies are at least as important as the intensity of natural selection in determining the probability of fixing desirable alleles.
RIBOSOMAL RNA CISTRON MULTIPLICITY AND NUCLEOLAR ORGANIZERS IN HEXAPLOID WHEAT
Authors: Mohan Jag , Flavell Richard B 
Published: January 2021

ABSTRACT
The ribosomal DNA (DNA complementary to ribosomal RNA) content of twelve different wheat genotypes has been studied. Some of these genotypes are aneuploids with deletions or additions of chromosomes bearing nucleolar organisers. The rDNA contents of these genotypes provide several examples of a clear departure from a correlation between the number of rRNA cistrons and the number of nucleolar organisers. Thus the number of rRNA cistrons per nucleolar organiser is not constant in wheat. Wheat DNA was found to have a mean buoyant density of approximately 1.702 g/cc for all genotypes studied and rRNA hybridized selectively to DNA of buoyant density approximately 1.710 g/cc. The thermal stabilities of all the rRNA/DNA hybrids were essentially identical.
α-HYDROXYACID OXIDASE GENETICS IN THE MOUSE: EVIDENCE FOR TWO GENETIC LOCI AND A TETRAMERIC SUBUNIT STRUCTURE FOR THE LIVER ISOZYME
Authors: Duley John , Holmes Roger S 
Published: January 2021

ABSTRACT
We have examined a polymorphism for liver GOX in inbred strains of the mouse Mus musculus. Genetic studies demonstrated that the two phenotypes for this enzyme present in BALB/C and NZC parental strains segregated as though they were controlled by codominant alleles at a single autosomal locus (GOX) which mapped closely to the agouti locus in linkage group V. Kidney HAOX activity is invariant in these inbred strains and is encoded by a separate genetic locus designated HAOX. BALB/C × NZC F1 hybrid mice exhibited three intermediate forms of liver GOX activity, in addition to the parental enzymes, which is consistent with a tetrameric subunit structure.
MUTATIONS AFFECTING SEXUAL CONJUGATION AND RELATED PROCESSES IN SACCHAROMYCES CEREVISIAE. I. ISOLATION AND PHENOTYPIC CHARACTERIZATION OF NONMATING MUTANTS
Authors: Mackay Vivian , Manney Thomas R 
Published: January 2021

ABSTRACT
Nonmating mutants were also isolated from haploid strains of yeast of both mating types. The mutants were characterized with respect to their ability to produce and respond to specific yeast sex factors, their ability to mate at low frequencies, and the ability of the low-frequency diploids to sporulate. Loss of the ability to mate by either mating type was invariably accompanied by the loss of one or more, and in some cases, all, of the above capabilities. The results strongly indicate that the sex factors are functionally involved in the conjugation process.
INTRACISTRONIC MAPPING OF ELECTROPHORETIC SITES IN DROSOPHILA MELANOGASTER: FIDELITY OF INFORMATION TRANSFER BY GENE CONVERSION
Authors: McCarron Margaret , Gelbart William , Chovnick Arthur 
Published: January 2021

ABSTRACT
A convenient method is described for the intracistronic mapping of genetic sites responsible for electrophoretic variation of a specific protein in Drosophila melanogaster. A number of wild-type isoalleles of the rosy locus have been isolated which are associated with the production of electrophoretically distinguishable xanthine dehydrogenases. Large-scale recombination experiments were carried out involving null enzyme mutants induced on electrophoretically distinct wild-type isoalleles, the genetic basis for which is followed as a nonselective marker in the cross. Additionally, a large-scale recombination experiment was carried out involving null enzyme rosy mutants induced on the same wild-type isoallele. Examination of the electrophoretic character of crossover and convertant products recovered from the latter experiment revealed that all exhibited the same parental electrophoretic character. In addition to documenting the stability of the xanthine dehydrogenase electrophoretic character, this observation argues against a special mutagenesis hypothesis to explain conversions resulting from allele recombination studies.
SEGMENTAL ANEUPLOIDY AND ENZYME ACTIVITY AS A METHOD FOR CYTOGENETIC LOCALIZATION IN DROSOPHILA MELANOGASTER
Authors: Stewart Barbara R , Merriam John R 
Published: January 2021

ABSTRACT
A method of mapping genes which specify enzymes without the necessity of obtaining genetic variants has been explored. Three enzymes whose structural genes have known genetic positions were chosen to see if the relationship between gene dosage and enzyme activity could be used as a tool in cytological localization. Zw, the gene specifying G6PD, is located in the X chromosome region, 18D-18F. The structural gene for 6PGD, Pgd, maps in the X chromosome bands 2C1-2E1. Idh-NADP, the gene which specifies IDH-NADP, is found on the third chromosome, in bands 66B-67C.
POPULATION STUDIES IN MICROORGANISMS I. EVOLUTION OF DIPLOIDY IN SACCHAROMYCES CEREVISIAE
Authors: Adams Julian , Hansche Paul E 
Published: January 2021

ABSTRACT
The relative adaptation of isogenic haploid and diploid strains of yeast was investigated in different sets of physiological conditions. When all nutrients were present in excess, no difference in the reproductive rates of isogenic haploid and diploid strains of yeast was detected in both optimal and non-optimal growth conditions. Competition between haploid and diploid strains of yeast was observed when growth was limited by the concentration of a single nutrilite. Under certain conditions when fitness (reproductive rate) is determined by transport of an essential nutrilite that exists in very low concentrations, diploid cells were selected against. These environmental conditions are similar to those found in offshore marine environments where nutrients are often present in extremely low concentrations. The fitness of diploid cells was estimated to be.93 ±.02 (haploid fitness = 1). The reduced fitness of diploid cells in this environment can be explained by the reduced surface area/volume ratio possessed by diploid cells in comparison to haploid cells. The fitnesses of haploid and diploid cells in these environments are closely correlated with geometric variations in these strains. These results are consistent with the hypothesis that diploid cells are simply double haploids, and diploidy per se does not confer any direct adaptive advantage. The mechanism of the evolution of diploidy as a dominant phase in the life cycle of higher plants and animals remains obscure.
THE a2m(r-pa-pu) ALLELE OF THE En-CONTROLLING ELEMENT SYSTEM IN MAIZE
Authors: Fowler Robert , Peterson Peter A 
Published: January 2021

ABSTRACT
The Enhancer (En) controlling element system in maize includes numerous alleles, one of which, a2m(r-pa-pu), was recovered as a derivative of the a2m(1 1511) allele. The behavior and composition of this allele is described. In the presence of the independently inherited regulatory element, En, the a2m(r-pa-pu) allele mutates and expresses in the aleurone purple, pale and colorless sectors within a colorless background. In the absence of En, the pigmentation is uniformly pale. Colored and colorless germinal mutations of the a2m(r-pa-pu) allele were recovered, although the derivative alleles tested did not respond to En. Uniformly colored derivatives, designated A2', arise only from states of a2m(r-pa-pu) that respond to an active En at relatively early stages in plant development, suggesting that somatic and germinal mutations may arise through similar events. Mutations to A2-expressing alleles appear to occur relatively late in plant development, that is, at or near meiosis, since recognizable mutant sectors do not appear on testcross ears. Kernels exhibiting such mutants are randomly distributed over the ear. The resulting A2' alleles express pigmentation ranging in a continual sequential series from dark pale to intense purple.
GENETIC DISSECTION OF SEGREGATION DISTORTION. I. SUICIDE COMBINATIONS OF SD GENES
Authors: Hartl Daniel L 
Published: January 2021

ABSTRACT
Two major loci in the Tft–cn region of an SD chromosome have been separated by recombination and identified. The allele at the left-hand locus on an SD chromosome is called Sd; the allele at the right-hand locus is called Rsp. Both Sd and Rsp are necessary to bring about a distortion of the segregation ratio in heterozygous SD males, although the particular degree of distortion exhibited by an SD chromosome is influenced by the constellation of polygenic modifiers of SD in the genome. The coupling phase of the alleles, Sd Rsp/Sd + Rsp +, produces about 89-90% of Sd Resp-bearing progeny. The repulsion phase, Sd Rsp +/Sd + Rsp, produces 10-20% of Sd Rsp +-bearing progeny. No coupling-repulsion effects between Sd and Rsp are apparent.