bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-LINKAGE OF A HUMAN GENETIC LOCUS THAT CORRECTS THE DNA SYNTHESIS LESION IN tsC1AGOH MOUSE CELLS
Authors: Giles Richard E , Ruddle Frank H 
Published: April 2021

ABSTRACT
GM 126 human diploid fibroblasts were fused with a heat-sensitive mouse cell mutant defective in DNA synthesis, and primary hybrids were selected at permissive and nonpermissive temperatures in HAT medium. Primary hybrids, primary hybrid clones back-selected in 8-azaguanine at the permissive temperature, and subclones of heat-resistant primary hybrids isolated under nonselective conditions or after 8-azaguanine treatment were tested for heat sensitivity, the expression of 26 human enzymes assigned to 19 different human chromosomes, and the presence of human chromosomes. Only the human X chromosome and X-linked marker enzymes exhibited a clear pattern of concordant segregation with the heat-resistant phenotype. On the basis of these observations, we have defined the human genetic locus that corrects the heat-sensitive lesion in tsC1AGOH as hrC1AGOH and have assigned this locus to the X chromosome. This observation provides the first instance where two selectable markers (heat resistance and 8-azaguanine sensitivity) are found on a single human chromosome and suggests that these markers may prove to be a valuable push-pull selective system of use in determining the linear arrangement of genes on human chromosomes by somatic cell genetics.
GENIC HETEROGENEITY WITHIN ELECTROPHORETIC "ALLELES" AND THE PATTERN OF VARIATION AMONG LOCI IN DROSOPHILA PSEUDOOBSCURA
Authors: Singh Rama S 
Published: April 2021

ABSTRACT
An investigation, similar to our previously reported xanthine dehydrogenase study, was undertaken to examine the extent of hidden genic variation at nine loci (five larval proteins, three esterases and one aldehyde oxidase) by sequential application of various electrophoretic criteria employing pH, gel concentration and buffer variation. Polymorphic loci appear to fall into two distinct groups: weakly polymorphic, including larval protein 6, 7, 8, 10 and 13 and esterase-1 and -6; and highly polymorphic, including esterase-5, Xdh and possibly Ao. Monomorphic loci may belong to a third group different from all polymorphic lori. Bogota, a geographical isolate that is reproductively isolated from the mainland population, was found to be genetically distinct at four of the ten loci examined in detail so far, including Xdh, whereas previously it was found to be genetically distinct at none. These results are discussed in the light of balancing selection, neutral and mutation-selection hypotheses of genic variation in natural populations.
THE GENETIC COVARIANCE BETWEEN CHARACTERS MAINTAINED BY PLEIOTROPIC MUTATIONS
Authors: Lande Russell 
Published: April 2021

ABSTRACT
A statistical genetic model of a multivariate phenotype i s derived to investigate the covariation of pleiotropic mutations with additive effects under the combined action of phenotypic selection, linkage and the mating system. Equilibrium formulas for large, randomly mating populations demonstrate that, when selection on polygenic variation is much smaller than twice the harmonic mean recombination rate between loci with interacting fitnesses, linkage disequilibrium is negligible and pleiotropy is the main cause of genetic correlations between characters. Under these conditions, approximate expressions of or the dynamics of the genetic covariances due to pleiotropic mutations are obtained. Patterns of genetic covariance between characters and their evolution are discussed with reference to data on polygenic mutation, chromosomal organization and morphological integration.
DIRECTIONALITY AND NONRECIPROCALITY OF CHI-STIMULATED RECOMBINATION IN PHAGE Λ
Authors: Stahl Franklin W , Stahl Mary M , Malone Robert E , Crasemann Jean M 
Published: April 2021

ABSTRACT
Chi's are genetic elements that stimulate generalized recombination in their locale in phage λ. All Chi's, wherever located on λ's chromosome, act asymmetrically in crosses blocked in DNA replication: (1) They stimulate exchange primarily to their left on the conventional λ map, and (2) the stimulated exchange is frequently nonreciprocal, the recombinant carrying the Chi element being produced less often than the complementary product.
A COMPARISON OF TWO-POINT, THREE-POINT AND DELETION MAPPING IN THE C CISTRON OF RHIZOBIOPHAGE 16–3, WITH AN EXPLANATION FOR THE RECOMBINATION PATTERN
Authors: Orosz LÁszlÓ , RostÁs Katalin , Hotchkiss Rollin D 
Published: April 2021

ABSTRACT
A general tendency for additivity prevailed in recombination frequencies for two-point fine-structure mapping of 14 mutants in the C cistron of Rhizobium meliloti phage 16-3, with little evidence of any marker effect. Intracistronic three-point mapping indicated that double crossovers are rare. Deletion mapping indicated that the two- and three-point mapping data gave the correct order of the mutations. A high frequency (5 to 8%) of c/c+ heterozygotic phage progenies was observed in standard crosses. This pattern implies formation of a relatively long region of heterozygosity. Together with the results of the three-point tests, it suggests certain properties of the branch migration and resolution steps envisioned in current mechanisms of recombination.
A CIS-ACTING MUTATION WITHIN THE MAT
a LOCUS OF SACCHAROMYCES CEREVISIAE THAT PREVENTS EFFICIENT HOMOTHALLIC MATING-TYPE SWITCHING
Authors: Mascioli Deborah Wygal , Haber James E 
Published: April 2021

ABSTRACT
Homothallic strains of Saccharomyces cerevisiae are able to switch from one mating-type to the other as frequently as every cell division. We have identified a cis-dominant mutation of the MATa locus, designated MATa-inc, that can be converted to MATα at only about 5% of the normal efficiency. In homothallic MATa-inc/mata* diploids, the MATa-inc locus switched to MATα in only one of 30 cases, while the mata* locus switched to MATα in all 30 cases. The MATa-inc mutation can be "healed" by a series of switches, first to MATα and then to a normal allele of MATa. These data are consistent with the "cassette" model of HICKS, STRATHERN and HERSKOWITZ (1977), in which mating conversions involve the transposition of wild-type copies of a or α information from silent genes elsewhere in the genome. The MATa-inc mutation appears to alter a DNA sequence necessary for the replacement of MATa by MATα. The MATa-inc mutation has no other effect on MATa functions. In heterothallic backgrounds, the mutation has no effect on the sensitivity to α-factor, synthesis of a-factor, expression of barrier phenotype or ability to mate or sporulate.—The MATa-inc allele does, however, exhibit one pleiotropic effect. About 1% of homothallic MATa-inc cells become completely unable to switch mating type because ofmutations at HMa, the locus proposed to carry the silent copy of α information.—In addition, we have isolated a less efficient allele of the HO gene.
REGION-SPECIFIC RECOMBINATION IN PHAGE T4. II. STRUCTURE OF THE RECOMBINANTS
Authors: Levy Jack N , Goldberg Edward B 
Published: April 2021

ABSTRACT
In this paper, we present results of crosses designed to elucidate the structure of recombinants in the tail-fiber region of bacteriophage T4, in which a glucosylation-dependent recombination mechanism is operative, and the cause of this "special" recombination in glucosylated crosses is discussed. We present evidence that, when phage are nonglucosylated, recombination in the tail-fiber region proceeds via long heteroduplex overlaps. Mismatched bases within such regions (in nonglucosylated phage) are repaired efficiently (as contrasted to those of glucosylated phage), bnt asymmetrically; that is, there may not be an equal probability of resolving the mismatch to mutant or wild type.
GENETIC ANALYSIS OF THE DUMPY COMPLEX LOCUS IN DROSOPHILA MELANOGASTER: COMPLEMENTATION, FINE STRUCTURE AND FUNCTION
Authors: Grace Dale 
Published: April 2021

ABSTRACT
An extensive genetic analysis of the dumpy locus is presented. This study includes complementation, fine structure mapping and allelic interaction. A number of complementing recessive lethals of the dp complex have been genetically mapped. Two alleles of the ol(v) type that complement l alleles map to the left portion of the locus. A number of olv alleles that complement both l and lv lethals map within the right portion of the locus.—Fine-structure analysis demonstrated that both olv and o alleles are distributed among various subloci. Evidence for spacer regions between subloci is presented.—An extensive discussion of the data considers whether the locus is unicistronic or multicistronic. The conclusion reached is that the locus is not a single functional cistron. The possibility of a single cistron encoding a multifunctional polypeptide is discussed.—The hypothesis is proposed that the left portion of the map and the l mutations function as regulatory sequences and that the right portion of the map encodes structural sequences.
GENETIC MAPPING OF A GROUP OF TEMPERATURE-SENSITIVE dna INITIATION MUTANTS IN BACILLUS SUBTILIS
Authors: Imada Sumi , Carroll Lynn E , Sueoka Noboru 
Published: April 2021

ABSTRACT
Recombination frequencies among temperature-sensitive dna mutants from various laboratories were analyzed, and eleven dna mutants were found to be closely linked. They are classified as group B dna mutants, since these are closely linked with dnaB19, originally isolated and approximately mapped near leuA8 by KARAMATA and GROSS (1970). However, the dnaB19 mutation itself has relatively high recombination frequencies with the other mutations, thus, we propose to subdivide the dnaB group into two subgroups—dnaBI, including ten mutants (dna-I, dna-3, dna-5, dna-17, dna-27, dna-51, dna-60, dna-62, dna-103 and dna-134) and dnaBII, including dnaB19. The map order of dnaB and markers in the vicinity was determined to be argA-citH-citC- phoP-phoR-polA-dnaBI-dnaBII-cilF-leuA-pheA.
MITOTIC RECOMBINATION IN YEAST: ISOLATION AND CHARACTERIZATION OF MUTANTS WITH ENHANCED SPONTANEOUS MITOTIC GENE CONVERSION RATES
Authors: Maloney Daniel H , Fogel Seymour 
Published: April 2021

ABSTRACT
Semi-dominant mutants displaying greatly elevated (up to 200-fold above control) levels of spontaneous mitotic recombination have been isolated in a disomic haploid strain of yeast heteroallelic at the arg4 locus. They are designated by the symbol MIC. The mutants variously exhibit associated sensitivity to UV and ionizing radiation and to methyl methanesulfonate, enhanced UV-induced mitotic recombination, and enhanced spontaneous forward mutation rates. Possible enzyme defects and involvement in repair and editing of DNA are discussed. The mutants are expected to simplify the analysis of recombination pathways in yeast.
DUPLICATED GENES PRODUCING TRANSPOSABLE CONTROLLING ELEMENTS FOR THE MATING-TYPE DIFFERENTIATION IN SACCHAROMYCES CEREVISIAE
Authors: Oshima Takehiro , Takano Isamu 
Published: April 2021

ABSTRACT
Mutation of the two homothallic genes, HMLα/HMLa and HMRa/HMRα, in homothallic strains of Saccharomyces cereuisiae was studied. Of 11 mutants of the HMLa gene, eight were due to a phenotypic mutation from HMLα to HMLa, i.e., a mutation causing a change in function of the original HML allele to that of the other HML allele (functional mutation), and three were due to a defective mutation at the HMLα gene, i.e., a mutation causing a non-functional allele (nonfunctional mutation). All 14 mutants of the HMRa gene, on the other hand, were due to a phenotypic mutation from HMRa to HMRα i.e., a functional mutation. Phenotypic reverse mutations, i.e., HMLa to HMLα and HMRα to HMRa, were also observed in the cultivation of EMS (ethyl methanesulfonate) treated spores having the HO HMRα HMLa genotype. Mutation from heterothallic cells to homothallism was observed in a nonfunctional mutant of the HMLα gene, by mutagenesis with EMS, but not in the functional mutants of the HMLα and HMRa genes or in the authentic strains having the α HO HMRα HMLα (α Hp) and a HO HMRa HMLa (a Hq) genotypes. These observations suggest that the functional mutation is not caused by the direct mutation from a homothallic allele to the opposite, but by replacement of a transposable genic element produced from a homothallic locus with a region of a different homothallic locus. These observations also support the controlling-element model and the cassette model, which have been proposed to explain the mating-type differentiation by the homothallic genes.
DEPENDENCE ON MATING TYPE FOR THE OVERPRODUCTION OF ISO-2-CYTOCHROME c IN THE YEAST MUTANT CYC7–H2
Authors: Rothstein Rodney J , Sherman Fred 
Published: April 2021

ABSTRACT
The CYC7-H2 mutation causes an approximately 20-fold overproduction of iso-2-cytochromo c in a and α haploid strains of the yeast Saccharomyces cerevisiae due to an alteration in the nontranslated regulatory region that is presumably contiguous with the structural region. In this investigation, we demonstrated that heterozygosity at the mating type locus, a /α or a/a/α/α, prevents expression of the overproduction, while homozygosity, a/a and α/α and hemizygosity, a/O and α/O, allow full expression of the CYC7-H2 mutation, equivalent to the expression observed in a and α haploid strains. There is no decrease in the overproduction of iso-2-cytochrome c in a/α diploid strains containing either of the other two similar mutations, CYC7-H1 and CYC7-H3. It appears as if active expression of one or another of the mating-type alleles is required for the overproduction of iso-2-cytochrome c in CYC7-H2 mutants.
GENETIC ANALYSIS OF MATING TYPE DIFFERENTIATION IN PARAMECIUM TETRAURELIA. II. ROLE OF THE MICRONUCLEI IN MATING-TYPE DETERMINATION
Authors: Brygoo Y , Sonneborn T M , Keller A M , Dippell R V , Schneller M V 
Published: April 2021

ABSTRACT
The two complementary mating types, 0 and E, of Paramecium tetrauretia are normally inherited cytoplasmically. This property has generally been interpreted to indicate the presence of cytoplasmic factors that determine macronuclear differentiation towards 0 or E . In these macronuclear-cytoplasmic interactions, the micronuclei were held to be unbiased and the determination to be established in the course of macronuclear development. In order to ascertain whether the micronuclei were actually neutral, amicronucleate clones were needed and a method to produce them was developed. In crosses between amicronucleate clones and normal micronucleate clones, we have observed regular deviations from cytoplasmic inheritance: the commonest deviation is that most 0 amicronucleate cells become E when they receive a micronucleus from an E partner. The data can be interpreted by assuming that the micronuclei are predetermined and that the apparent "cytoplasmic" inheritance of the two mating types is due, in E cells, to E-determining factors present in the cytoplasm and in the nucleus; and, in 0 cells, to 0-determining factors present only or mainly in the nucleus.
A SIMULATION STUDY OF TRUNCATION SELECTION FOR A QUANTITATIVE TRAIT OPPOSED BY NATURAL SELECTION
Authors: Minvielle Francis 
Published: April 2021

ABSTRACT
A quantitative character controlled at one locus with two alleles was submitted to artificial (mass) selection and to three modes of opposing natural selection (directional selection, overdominance and underdominance) in a large random-mating population. The selection response and the limits of the selective process were studied by deterministic simulation. The lifetime of the process was generally between 20 and 100 generations and did not appear to depend on the mode of natural selection. However, depending on the values of the parameters (initial gene frequency, selection intensity, ratio of the effect of the gene to the environmental standard deviation, fitness values) the following outcomes of selection were observed: fixation of the allele favored by artificial selection, stable nontrivial equilibrium, unstable equilibrium and loss of the allele favored by artificial selection. Finally, the results of the simulation were compared to the results of selection experiments.
FUNCTIONAL EQUIVALENCE AND CO-DOMINANCE OF HOMOTHALLIC GENES HMα/hmα AND HM
a/hm
a IN SACCHAROMYCES YEASTS
Authors: Harashima Satoshi , Oshima Yasuji 
Published: April 2021

ABSTRACT
The specificity of mating type in Saccharomyces yeasts is controlled by a pair of alleles, a and α, on chromosome III. They are mutually interconverted by the function of three kinds of homothallic genes, each consisting of a single pair of alleles, HO/ho, HMα/hmα and HMa/hma. For the a to α conversion, HO HMα HMa, HO hmα HMa and HO hmα hma genotypes are effective; whereas, the α to a conversion occurs in HO HMα HMa, HO HMα hma and HO hmα hma cells. To explain these observations, Naumov and Tolstorukov (1973) and Harashima, Nogi and Oshima (1974) suggested that hma and HMα are functionally equivalent and effective for the α to a conversion in combination with HO; whereas, hmα and HMa are functionally equivalent and effective for the a to α conversion with the function of HO. To test this idea and to compare it with two other possible mechanisms, some of the tetrad segregants from four kinds of a/a/α/α tetraploids homozygous for the HO allele and for one of the HMα/hmα and HMa/hma loci, while heterozygous for the other one with +/+/-/- configuration, were investigated with respect to their thallism by self-sporulation. Results indicated the functional equivalence of both the HMα and hma alleles and the hmα and HMα alleles in mating-type conversion, and the co-dominance of the alleles of each locus. From these findings and other data, we agree with the revision of the nomenclature of the HMα/hmα and HMa/hma genes to HMRa/HMRα and HMLα/HMLa, respectively.
TECHNIQUES AND MARKER GENES FOR USE IN MACROCYST GENETICS WITH POLYSPHONDYLIUM PALLIDUM
Authors: Francis David 
Published: April 2021

ABSTRACT
Previous work has shown that genetic exchange occurs in the macrocyst of Polysphondylium pallidum, as in species of Dictyostelium. These studies are extended here. Mutants resistant to six different poisons have been isolated for use as genetic markers. A replica-plating technique has been engineered whereby 14 progeny clones growing on a master plate may be simultaneously transferred to test plates containing individual poisons. Germination percent of macrocysts has been greatly increased by the presence of a growing fungus during the resting stage. These means have been used to analyze crosses showing that: (1) Vegetative amebae are haploid, at least at the three marker loci tested. (2) Amebae emerging from a single macrocyst are identical about 90% of the time. (3) Any single combination of parental markers may emerge from a given macrocyst, and all combinations appear in approximately equal frequencies. These findings suggest that normally one of four nuclei produced by meiosis survives in every macrocyst and that all markers examined are unlinked. (4) About 10% of the macrocysts germinate to give two or more classes of progeny. These may result from the presence of a second zygote in the macrocyst or from the survival of two nuclei after meiosis. (5) If genetic exchange occurs during spore formation or microcyst formation, its frequency is low (&lt;0.01%).
unc-93(e1500): A BEHAVIORAL MUTANT OF CAENORHABDITIS ELEGANS THAT DEFINES A GENE WITH A WILD-TYPE NULL PHENOTYPE
Authors: Greenwald Iva S , Horvitz H Robert 
Published: April 2021

ABSTRACT
The uncoordinated, egg-laying-defective mutation, unc-93(e1500) III, of the nematode Caenorhabditis elegans spontaneously reverts to a wild-type phenotype. We describe 102 spontaneous and mutagen-induced revertants that define three loci, two extragenic (sup-9 II and sup-10 X) and one intragenic. Genetic analysis suggests that e1500 is a rare visible allele that generates a toxic product and that intragenic reversion, resulting from the generation of null alleles of the unc-93 gene, eliminates the toxic product. We propose that the genetic properties of the unc-93 locus, including the spontaneous reversion of the e1500 mutation, indicate that unc-93 may be a member of a multigene family. The extragenic suppressors also appear to arise as the result of elimination of gene activity; these genes may encode regulatory functions or products that interact with the unc-93 gene product. Genes such as unc-93, sup-9 and sup-10 may be useful for genetic manipulations, including the generation of deficiencies and mutagen testing.
MEIOTIC BEHAVIOR OF COMPOUND AUTOSOMES IN FEMALES OF DROSOPHILA MELANOGASTER: INTERCHROMOSOMAL EFFECTS AND THE SOURCE OF SPONTANEOUS NONSEGREGATION
Authors: Harger Hideh , Holm David G 
Published: April 2021

ABSTRACT
In females of Drosophila melanogaster, compound autosomes enter the repulsion phase of meiosis uncommitted to a particular segregation pattern because their centromeres are not restricted to a bivalent pairing complex as a consequence of crossing over. Their distribution at anaphase, therefore, is determined by some meiotic property other than exchange pairing, a property that for many years has been associated with the concept of nonhomologous pairing. In the absence of heterologous rearrangements or a free Y chromosome, C(3L) and C(3R) are usually recovered in separate gametes, that is as products of meiotic segregation. Nevertheless, there is a regular, albeit infrequent, recovery of reciprocal meiotic products (the nonsegregational products) that are disomic and nullosomic for compound thirds. The frequency of these exceptions, which is normally between 0.5 and 5.0%, differs for the various strains examined, but remains constant for any given strain. Since previous studies have not uncovered a cause for this base level of nonsegregation, it has been referred to as the spontaneous frequency. In this study, crosses between males and females whose X chromosomes, as well as compound autosomes, are differentially marked reveal a highly significant positive correlation between the frequency of compound-autosome nonsegregation and the frequency of X-chromosome nondisjunction. However, an inverse correlation is found when the frequency of nondisjunction is related to the frequency of crossing over in the proximal region of the X chromosome. These findings have been examined with reference to the distributive pairing and the chromocentral models and interpreted as demonstrating (1) that nonsegregational meiotic events arise primarily as a result of nonhomologous interactions, (2) that forces responsible for the segregation of nonhomologous chromosomes are properties of the chromocentral region, and (3) that these forces come into expression after the exchange processes are complete.
RECOMBINATION AND CHROMOSOME SEGREGATION DURING THE SINGLE DIVISION MEIOSIS IN SPO12–1 AND SPO13–1 DIPLOIDS
Authors: Klapholz Sue , Esposito Rochelle Easton 
Published: April 2021

ABSTRACT
This paper reports a study of chromosome segregation and recombination during sporulation of spo12—1 and spo13–1 diploid strains of S. cerevisiae. These strains undergo a single division to form asci containing two diploid or near-diploid spores. The segregation of centromere-linked markers in the two-spored (dyad) products indicates that the division is generally equational. However, in a small percentage of the spo12–1 and spo13–1 cells, it appears that a meiosis I-like division occurs. Aberrant segregation of the MAT locus on chromosome III, yielding a monosomic and a trisomic spore pair, occurs in 12% of all dyads. The segregation patterns of markers at various distances from their centromeres and several pairs of markers on the same chromosome indicate that recombination takes place in both strains at nearly standard meiotic levels.