bluuebunny/crossref_metadata_2025_split huggingface dataset:
ESTERASE VARIATIONS BETWEEN THE 14 SYNGENS OF PARAMECIUM AURELIA UNDER AXENIC GROWTH
Authors: Allen S L , Farrow S W , Golembiewski P A 
Published: January 2021

ABSTRACT
Under axenic growth all 14 syngens of Paramecium aurelia have 4 types of esterases. The three major types (A, B and cathodal C) vary independently in electrophoretic mobility among the syngens. Using these three esterases, stocks can be keyed to a syngen, except for the groupings 1-3-5 and 7-13. Using 5 other enzymes only syngens 1 and 5 cannot be distinguished. Most syngens differ from each other in 6 out of the 8 enzymes. An axenically-grown stock of Paramecium multimicronucleatum collected in Costa Rica has the same types of esterases as P. aurelia. Two of the types (A and C) are similar in mobility to those found in syngens 7 and 13, but its B esterase differs in mobility from all the known syngens of P. aurelia.
RESOLVING THE ENIGMA OF MULTIPLE MUTANT SECTORS IN STAMEN HAIRS OF TRADESCANTIA
Authors: Mericle L W , Mericle R P 
Published: January 2021

ABSTRACT
Mutant sectors in stamen hairs of Clone 02 Tradescantia are designated as "multiple sectors" when two or more occupy the same hair, separated by nonmutant cells. Statistical analyses show that most multiple sectors do not arise as chance associations of independent events: when the frequency of stamens with two or more sectors is lowest, the probability that the sectors will be located in the same, rather than in different, hairs is highest. Ontogenetically, the ratio of sector pairs in different hairs to pairs in the same hair is highest in that period of response to acute irradiation prior to the appearance of entirehair sectors; thereafter, the ratio subsides, approaching that of spontaneous mutation and indicating that the initiating event takes place early in hair development. Most mononemic chromosome models will not account for the production of multiple mutant and non-mutant sectors, dispersed along a linear structure such as a stamen hair, following a single mutational event. Consideration is given to two models (one mononemic, and the other dinemic) which will readily provide the possibilities for either the immediate segregation of mutant and non-mutant cells, or for the perpetuation in daughter nuclei of a "heterozygous" chromosome capable of segregation at some later mitosis. The dinemic model is preferred because it affords operation of the mutation mechanism (including breakage and deletion) at either the DNA molecule or subunit level.
SELECTIVE SOMATIC ELIMINATION OF NICOTIANA GLUTINOSA CHROMOSOMES IN THE F1 HYBRIDS OF N. SUAVEOLENS AND N. GLUTINOSA
Authors: Gupta S B , Gupta Pratibha 
Published: January 2021

ABSTRACT
The F, hybrids of Nicotiana suaveolen (subgenus Petunioides, 2n = 32) and N. glutinosa (subgenus Tabacum, 2n = 24), were examined during their development, from seedlings to mature plants. It was observed that in the hybrids, there was a progressive change of dominant N. glutinosa morphological characteristics towards those of N. suaveolens, in leaf shape, stem, flower color and branching pattern. A study of mitotic chromosomes in the root-tips and in very young anthers of the mature plants indicated a significantly high average frequency of aberrant mitotic anaphases (bridges and fragments, 12% and 11 % respectively). As a consequence of this phenomenon, variability in the number and size of chromosomes was observed in the PMC's and in mitotic metaphases (29-24 chromosomes). In order to establish whether the N. glufinosa chromosomes were preferentially last, a karyological study of the parents and their F, hybrids was carried out and it was established that the F, hybrids were losing N. glutinosa chromosomes preferentially. A mechanism was suggested for the loss of these chromosomes by means of a chromatid type of breakage-fusion-bridge cycle (b-f-b cycle) and initiation of the b-f-b cycle in the hybrid due to an interaction of the regulatory mechanism of DNA replication in the haploid genomes of the parental species. However, loss of these chromosomes owing to interaction of certain genes from the two parental species cannot be ruled out.
MEIOTIC BEHAVIOR OF ASYMMETRIC DYADS IN THE MALE DROSOPHILA
Authors: Zimmering S , Bendbow E B 
Published: January 2021

ABSTRACT
Crossing over in the interstitial region of the heterozygous V4 translocation in Drosophila melanogaster generates asymmetric dyads each consisting of a shorter and a longer chromatid It was shown previously that in the female the shorter is recovered preferentially (ZIMMERING 1955); the present work suggests that the same occurs in the male as weI1. The mechanism in the female is envisioned as involving the non-random inclusion of the shorter chromatid into the functional egg (NOVITSK 1951); in the male, the two formal possibilities appear to be (1) that some proportion of sperm carrying the longer chromatid derived from an asymmetric dyad undergoes dysfunction, or (2) the longer chromatid is preferentially included into regularly-produced nonfunctional sperm, the nonfunctionality set up at the second division and distinguishing second division daughter cells.
INHERITANCE OF ALPHA-GLYCEROPHOSPHATE DEHYDROGENASE IN THE PINK SALMON, ONCORHYNCHUS GORBUSCHA (WALBAUM)
Authors: Aspinwall Nevin 
Published: January 2021

ABSTRACT
Genetic crosses of alpha-glycerophosphate dehydrogenase (alpha-GPDH) phenotypes in the pink salmon, Oncorhynchus gorbuscha (Walbaum), reveal that this enzyme is encoded by a single locus with two codominant alleles (Slow and Fast). The significance of single gene control of alpha-GPDH is discussed in relation to the purported tetraploid nature of the salmonids.
EVIDENCE FOR LINKAGE DISEQUILIBRIUM MAINTAINED BY SELECTION IN TWO NATURAL POPULATIONS OF DROSOPHILA SUBOBSCURA
Authors: Zouros E , Krimbas C B 
Published: January 2021

ABSTRACT
One island and one mainland population of Drosophila subobscura were found polymorphic at the XDH (xanthine dehydrogenase) and the A0 (aldehyde oxidase) loci. It was observed that one allele at the XDH locus, which has a low frequency in both populations, is nonrandomly associated with the alleles at the A0 locus. Two lines of evidence support the thesis that this linkage disequilibrium is due to epistasis rather than random drift: (I)D or r, measures of the disequilibrium, have the same sign and magnitude in both populations. (2) The linkage disequilibrium is not due to inversions. Inversions segregating on the chromosome carrying XDH and A0 have been separated into two classes, between which exchange of alleles at the two loci is suppressed. Linkage disequilibrium for XDH and A0 was observed within each class. In the absence of any exchange of alleles, these disequilibria must have arisen and been maintained independently. The suggestion is made that the epistatic disequilibrium results from the close structural and physiological relationship which exists between the tn-o enzymes.
THE ANALYSIS OF QUANTITATIVE TRAITS FOR SIMPLE GENETIC MODELS FROM PARENTAL, F1 AND BACKCROSS DATA
Authors: Elston R C , Stewart John 
Published: January 2021

ABSTRACT
The following models are considered for the genetic determination of quantitative traits: segregation at one locus, at two linked loci, at any number of equal and additive unlinked loci, and at one major locus and an indefinite number of equal and additive loci. In each case an appropriate likelihood is given for data on parental, F1 and backcross individuals, assuming that the environmental variation is normally distributed. Methods of testing and comparing the various models are presented, and methods are suggested for the simultaneous analysis of two or more traits.
TEMPERATURE-SENSITIVE MUTANTS FOR THE REPLICATION OF PLASMIDS IN ESCHERICHIA COLI II. PROPERTIES OF HOST AND PLASMID MUTATIONS
Authors: Kingsbury David T , Sieckmann Donna G , Helinski Donald R 
Published: January 2021

ABSTRACT
Host mutations in Escherichia coli K12 selected for the temperature-sensitive replication of the bacterial plasmid colicinogenic factor E1 (ColE1) exhibit a pleiotropic effect with respect to the effect of the mutation on other extrachromosomal elements. The mutations also vary with respect to the time of incubation of the cells at 43°C required for complete cessation of COlE1, DNA synthesis. While the synthesis of the bacterial chromosome appears unaffected, supercoiled ColE1 DNA replication stops immediately in some mutants and gradually decreases during several generations of cell growth before stopping in others. Mutations isolated in the ColE1 plasmid resulted in only a gradual cessation of ColE1 DNA synthesis over several generations of cell growth at 43°C. Conjugal transfer of the ColE1 and COlV factors occurs normally in the host mutants when the transfer is carried out at the permissive temperature; however, the presence of a group I mutation in the donor cell prohibited conjugal transfer of either plasmid DNA at 43°C to a normal recipient cell. Similarly, the presence of this mutation in the recipient prevented the establishment of COlE1 or COlV in the mutant recipient cell upon conjugation with a normal donor at 43°C. Various host COlE1, replication mutants carrying either ColE1 or ColE2 were also defective in the mitomycin Cinduced production of colicin E1 or colicin E2 at 43°C. The majority of the host mutations examined exhibited a temperature sensitivity to growth in deoxycholate in addition to the inhibition of plasmid DNA replication, suggesting a membrane alteration in these mutants when grown at the restrictive temperature.
THE TIMING OF TEMPERATURE SENSITIVITY OF LEAKY FERTILITY FACTOR MUTATIONS IN MALE DROSOPHILA MELANOGASTER
Authors: Frankel Anne W Koopmans 
Published: January 2021

ABSTRACT
Some of the mutations of the male fertility factors on the Y chromosome give rise to a small proportion of fertile males, each of which produces only a small number of progeny. Many of these mutations are temperature-sensitive, producing a larger proportion of fertile males at 25°C than at 19°C. One of these mutants was carefully analyzed and it was found that only sperm which mature in the first five days of adult life can effect fertilization, regardless of the temperature regimen. A unique temperature-sensitive period was localized to the mid-pupal stage by single twenty-four-hour 25°C treatments applied at various times in the life cycle to flies otherwise grown at 19°C. The temperature sensitivity associated with this pupal sensitive period is adequate to account for all of the difference in fertility between flies. grown continuously at the two temperatures. The timing of the temperature-sensitive process in combination with a cytological study of spermiogenesis indicates that temperature sensitivity occurs after the first meiotic metaphase during a spermatid stage. Thus it affects some post-transcriptional event in the expression of the phenotype of the fertility factor.
EFFECTS OF POPULATION SIZE AND SELECTION INTENSITY ON CORRELATED RESPONSES TO SELECTION FOR POSTWEANING GAIN IN MICE
Authors: Eisen E J , Hanrahan J P , Legates J E 
Published: January 2021

ABSTRACT
Correlated responses to selection for postweaning gain in mice were studied to determine the influence of population size and selection intensity. Correlated traits measured were three-, six- and eight-week body weights, litter size, twelve-day litter weight, proportion infertile matings and two indexes of reproductive performance. In general, the results agreed with observations made on direct response: correlated responses in the body weight traits and litter size increased as (1) selection intensity increased and (2) effective population size increased. Correlated responses in the body weight traits and litter size were positive in the large population size lines (16 pairs), as expected from the positive genetic correlation between these traits and postweaning gain. However, several negative correlated responses were observed at small population sizes (one and two pairs). Within each level of selection intensity, traits generally associated with fitness tended to decline most in the very small populations (one and two pairs) and in the large populations (16 pairs) for apparently different reasons. The fitness decline at the small effective population sizes was attributable to inbreeding depression. In contrast, it was postulated that the fitness decline at the large effective population size was due to selection moving the population mean for body weight and a trait positively correlated genetically with body weight (i.e., percent body fat) away from an optimum
TEMPERATURE-SENSITIVE MUTANTS FOR THE REPLICATION OF PLASMIDS IN ESCHERICHIA COLI I. ISOLATION AND SPECIFICITY OF HOST AND PLASMID MUTATIONS
Authors: Kingsbury David T , Helinski Donald R 
Published: January 2021

ABSTRACT
Temperature-sensitive mutants of Escherichia coli defective in the replication of the plasmid colicinogenic factor E1 (ColE1) were isolated following mutagenesis of E. coli K12 strain carrying the ColE1 factor. Following the mutagenic treatment an enrichment procedure utilizing the replacement of thymine with bromouracil in the ColE1 DNA duplicated at the restrictive temperature was used. The mutants isolated following this enrichment step were the result of a mutation event either in the host chromosome or in the ColE1 plasmid. The host mutants fell into three phenotypic classes based on the effect each mutation had on the maintenance of a variety of other extrachromosomal DNA elements. Phenotypic class I mutations affected all E. coli plasmids, both the I and F sex factor types as well as the ColE1 factor. Phenotypic class II mutations affected the maintenance of the ColE1 and the F sex factor type plasmids and not the I type, while phenotypic class III mutations affected only ColE1 replication. None of these mutations was found to have a significant effect on the replication of the E. coli chromosome. The plasmid-linked mutations fell into two phenotypic classes on the basis of the ability of the Flac episome to complement the mutation in the ColE1 plasmid.
MUTATIONAL ANALYSIS OF MATING TYPE INHERITANCE IN SYNGEN 4 OF PARAMECIUM AURELIA
Authors: Byrne Bruce C 
Published: January 2021

ABSTRACT
Six genic mutations restricting clones to mating type VII (O) were isolated in syngen 4, Paramecium aurelia. The only three extensively tested were neither allelic nor closely linked. A second type of mutation, allelic to one of the O restricted mutants, was also found. Clones homozygous for this mutant gene were selfers, producing both O and E (VIII) mating types, but only when they were progeny of mating type E parental clones. While all seven mutant genes behaved as recessives in monohybrid crosses, clones heterozygous at two different loci often demonstrated an unanticipated phenotype: selfing. The significance of the findings is discussed in relation to mating type determination and the evolution of mating type systems.
REGULATORY SEROTYPE MUTATIONS IN TETRAHYMENA PYRIFORMIS, SYNGEN 1
Authors: Doerder F P 
Published: January 2021

ABSTRACT
A method utilizing allelic exclusion has been developed to isolate mutants of Tetrahymena pyriformis, syngen 1, in which the normal pattern of expression of mutally exclusive surface antigens is altered. Cells homozygous for the recessive mutant allele R-1r do not express the L, H and T serotypes when grown under conditions appropriate for their expression. Rather, a new immobilization antigen, r, is expressed. Cells homozygous for the recessive mutant allele R-3r also express the r antigen instead of H serotypes, but are normal in their expression of T antigens. Genetic analyses show that R-1 and R-3 are not closely linked, that R-1 is linked to T by 9.3 units, and that R-3 may be loosely linked to the mt locus. Different linkage values were obtained, however, when different inbred laboratory strains were used, suggesting the possible existence of crossover modifying genes. The rates of assortment of R-1R/R-1r and R-3R/R-3r heterozygotes into pure sublines expressing either H or r serotypes are close to the values observed for the differentiation of heterozygotes at other loci. The data confirm the previous observation that genetic coupling relationships are not maintained in macronuclear phenotypes and are consistent with the hypothesis that the macronucleus contains 45 assorting subunits. The assortment of the double heterozygote R-1R/R-1r, R-3R/R-3r at Rf=0.0112 suggests that the units of assortment are not individual genetic loci or chromosome fragments, but that the units may be complete genomes.
TRANSPOSITION OF THE ARSENATE RESISTANCE LOCUS OF BACILLUS SUBTILIS STRAINS 23 AND 168
Authors: Adams Alice 
Published: January 2021

ABSTRACT
Wild-type Bacillus subtilis strains 23 and 168 are resistant to high concentrations of sodium arsenate. The genetic configurations of the arsenate resistance loci of these two related strains of B. subtilis have been characterized. The transformable 168 strain has a single resistance locus which maps between phe and aroD in the terminal third of the genome. In contrast, strain 23 is shown to have its single arsenate resistance locus between purB and thr in the first third of the bacterial chromosome. Moreover, in strain 23 the chromosomal segment equivalent to the phe-linked asa region of 168 strains is missing. DNA isolated from 23 strains is able to transform 168 arsenate-sensitive strains to resistance and the heterologous 23 DNA is found to preferentially establish a new purB linked asa locus in such transformed cells. Thus, the majority of phenotypically arsenate-resistant cells recovered after exposure of competent 168 sensitive mutants to 23 DNA are "heterozygous" and still retain their phe-linked mutated asa locus. The tolerance of several of these heterologously transformed hybrid strains to arsenate suggests that the 168 and 23 asa gene products are similar, and a transposition model for the evolution of arsenate resistance in B. subtilis is proposed.
SEGREGATION OF INDUCED FRAMESHIFT MUTATIONS AND THE SEQUENCE OF GENE REPLICATION IN ESCHERICHIA COLI K12
Authors: Hoess Ronald H , Herman Robert K 
Published: January 2021

ABSTRACT
We have constructed a strain of E. coli K12 carrying six mutations induced by the acridine half-mustard ICR-191. The mutations are widely spaced on the E. coli linkage map and are all easily reverted by ICR-191. Mapping of ten independent revertants for each of five markers indicated that the reversions induced by ICR-191 occurred near the original mutations. Exponentially and nonsynchronously growing cultures of this strain were exposed to ICR-191 for 0.85 generation, quickly washed free of mutagen, and resuspended in the original medium minus mutagen. Total viable cell number maintained its exponential increase both during and immediately after exposure to mutagen, whereas the number of revertants of any particular type remained constant for a characteristic period after removal of mutagen before finally assuming an exponential increase. Theoretically, the length of such a segregation lag should depend on the position of the particular reverted gene in the sequence of gene replication: the earlier a gene is replicated in the chromosome replication cycle, the longer its segregation lag should be. Our results are consistent with this prediction and fit a unidirectional, clockwise replication scheme with an origin between 55 and 74 min on the E. coli linkage map. The results also fit a very asymmetric bidirectional replication scheme.
THE INDUCTION OF MITOTIC GENE CONVERSION BY X-IRRADIATION OF HAPLOID SACCHAROMYCES CEREVISIAE
Authors: Campbell D A 
Published: January 2021

ABSTRACT
Mitotic recombination in Saccharomyces cerevisiae was examined by means of experiments in which one of the haploid parents was X-irradiated prior to zygote formation. By this method radiation-induced lesions are restricted to only one of the two non-sister chromatids that may be expected to undergo mitotic exchange in the diploid. The principal results of this work are: (1) X-irradiated haploid cells that are incapable of further vegetative growth (colony formation) are efficiently rescued into viable diploids by mating with unirradiated haploid cells. (2) X-rays delivered to only one of the two haploid parents are recombinogenic in the resultant diploid. The frequency of detected recombinational events increases as a probable linear function of the X-ray dose. (3) A majority of the induced recombinational events are nonreciprocal in nature (mitotic gene conversion). These results complement those obtained from X-irradiation of the vegetative diploid itself, where the induced genetic exchanges are principally reciprocal.
GENETIC CONTROL OF THE CELL DIVISION CYCLE IN YEAST: V. GENETIC ANALYSIS OF cdc MUTANTS
Authors: Hartwell Leland H , Mortimer Robert K , Culotti Joseph , Culotti Marilyn 
Published: January 2021

ABSTRACT
One hundred and forty-eight temperature-sensitive cell division cycle (cdc) mutants of Saccharomyces cerevisiae have been isolated and characterized. Complementation studies ordered these recessive mutations into 32 groups and tetrad analysis revealed that each of these groups defines a single nuclear gene. Fourteen of these genes have been located on the yeast genetic map. Functionally related cistrons are not tightly clustered.
Mutations in different cistrons frequently produce different cellular and nuclear morphologies in the mutant cells following incubation at the restrictive temperature, but all the mutations in the same cistron produce essentially the same morphology. The products of these genes appear, therefore, each to function individually in a discrete step of the cell cycle and they define collectively a large number of different steps.
The mutants were examined by time-lapse photomicroscopy to determine the number of cell cycles completed at the restrictive temperature before arrest. For most mutants, cells early in the cell cycle at the time of the temperature shift (before the execution point) arrest in the first cell cycle while those later in the cycle (after the execution point) arrest in the second cell cycle. Execution points for allelic mutations that exhibit first or second cycle arrest are rather similar and appear to be cistron-specific. Other mutants traverse several cycles before arrest, and its suggested that the latter type of response may reveal gene products that are temperature-sensitive for synthesis, whereas the former may be temperature-sensitive for function.
The gene products that are defined by the cdc cistrons are essential for the completion of the cell cycle in haploids of a and α mating type and in a/α diploid cells. The same genes, therefore, control the cell cycle in each of these stages of the life cycle.