bluuebunny/crossref_metadata_2025_split huggingface dataset:
RIBOSOMAL DNA AMOUNTS IN PISUM SATIVUM
Authors: Cullis C A , Davies D Roy 
Published: April 2021

ABSTRACT
Different varieties of peas have different proportions of rDNA in their genomes; there is no obvious correlation between the proportions and seed or leaf size. The rDNA proportions in root tips, seedlings, leaves and in the cotyledon cells of high DNA content, were compared in four varieties. In three, there was no difference between tissues; the fourth showed an amplification of rRNA genes in the cells of high DNA content of the seed cotyledon, and also in the cells of young but not of older leaves. The fourth variety was the one that had the lowest proportion of rDNA of all those examined. Studies of the tissues of hybrids between genotypes with "low" and "high" proportions of rDNA showed that heterozygotes had the "high" value, showing again the occurrence of an amplification phenomenon.
INTEGRATION, AT HAG OR ELSEWHERE, OF H2 (PHASE-2 FLAGELLIN) GENES TRANSDUCED FROM SALMONELLA TO ESCHERICHIA COLI
Authors: Enomoto Masatoshi , Stocker Bruce A D 
Published: April 2021

ABSTRACT
A fla mutant of E. coli K12 was given fla + and H1-i by phage P1kc cotransduction from S. typhimurium, then made Fla- by transduction of ah1 from S. typhimurium. Motile clones expressing a Salmonella phase-2 antigen, e,n,x or 1,2, were obtained from the K12 i ah1 (therefore Fla-) line by P1kc transduction of flagellin-specifying genes, H2-e,n,x or H2–1,2, from Salmonella donors. Of eighteen such transductants sixteen failed to show phase variation, and on transduction back to Salmonella each structural gene for a phase-2 flagellin (or at least for its antigenically determinant part) now behaved as an allele of H1, presumably in consequence of incorporation in the hag region of the K12 recipient, in place of H1-i ah1 . The e,n,x- and 1,2-specifying genes were shown to have been integrated in the K12 chromosome without the linked H1-repressor gene or the adjacent vh2 gene (controlling rate of phase-variation) and they responded to the repressing activity of an H2 allele elsewhere in the cell, in this respect resembling H1 alleles of Salmonella or hag alleles of E. coli. Two K12 e,n,x transductants had flagellin-specifying genes which when transduced back to Salmonella were integrated at H2; they are inferred to have resulted from integration of H2-e,n,x in the K12 chromosome elsewhere than the hag region. These two clones showed phase variation, between a Fla+ phase, with antigen e,n,x, and a Fla- phase (with e,n,x determinant in the nonactive state and the determinant of antigen i inactivated by ah1). The two integrated e,n,x genes when in the "active" state retained the ability to repress expression of exogenote H1 alleles, which indicates that the closely linked H1-repressor gene also was integrated. One of the two exceptional transductants derived its e,n,x gene from a Salmonella donor with the linked vh2 - gene, which in Salmonella almost entirely prevents change of phase, and transduction of this e,n,x gene back to Salmonella recipients proved that vh2 - had been incorporated into the E. coli chromosome along with the e,n,x determinant and the H1-repressor gene. The high frequency of change of phase (Fla+↔Fla-) in the K12 e,n,x vh2 - transductant concerned suggests that vh2 - fails to prevent frequent change of state of the phase-determinant part of H2 when vh2 - and H2 are incorporated in the E. coli chromosome.
POPULATION DIFFERENTIATION UNDER THE CHARGE STATE MODEL
Authors: Brown A H D , Marshall D R , Weir B S 
Published: April 2021

ABSTRACT
The extent of divergence between partially isolated sub-populations for electrophoretically detectable alleles was formulated assuming the island model of migration and the charge state model of mutation. At equilibrium the ratio of the variance of charge between the means of k different islands to the average within-island variance of charge was shown to be approximately 4Nemk 2/(k-1)2 where Ne is the effective size of each island population and m is the migration rate. This ratio was calculated from published data for eight polymorphic loci in six island populations of Drosophila willistoni . Under the assumption that all variants are selectively neutral, migration rates of greater than 10 adults per generation per island are required to explain the observed similarity of the allelic profiles in D. willistoni . Since the islands studied appear to be virtually completely isolated it was concluded either that the observed protein variants are adaptive and maintained in populations by some form of balancing selection or that the observed variants themselves are neutral but natural selection acts to restrict the appearance of more extreme variants in the charge carried.
GENE FLOW AND SELECTION IN A TWO-LOCUS SYSTEM
Authors: Slatkin Montgomery 
Published: April 2021

ABSTRACT
A model of gene flow and selection in two linked loci is analyzed. The problems considered are the effects of linkage on the clines in frequencies at the two loci and the role of gene flow in producing linkage disequilibrium between the loci. Also, the possible significance of linkage as a mechanism for permitting a population of "track" spatial changes in the environment is considered. The results are that when the recombination fraction between the loci is of the same order of magnitude as the selection coefficients or smaller, then linkage is important in determining the gene frequencies and a substantial amount of linkage disequilibrium is present in the cline. Depending on the spatial pattern of selection on the two loci, linkage can either decrease or increase a population's response to local selection.
ISOLATION AND GENETIC ANALYSIS OF MUTANT STRAINS OF CHLAMYDOMONAS REINHARDI DEFECTIVE IN GAMETIC DIFFERENTIATION
Authors: Goodenough Ursula W , Hwang Carol , Martin Howard 
Published: April 2021

ABSTRACT
Impotent mutant strains of Chlamydomonas reinhardi, mating-type (mt) plus, are described that have normal growth and motility but fail to differentiate into normal gametes. Procedures for their isolation and their genetic analysis are described. Five of the imp strains (imp-2, imp-5, imp-6, imp-7, and imp-8) exhibit no flagellar agglutination when mixed with mt - or mt + gametes; these strains have been induced to form rare zygotes with mt - gametes and the mutations are shown to be unlinked to the mt locus (with the possible exception of imp-7). Two of the strains (imp-3 and imp-4) carry leaky mutations that affect cell fusion; neither mutation is found by tetrad analysis to be linked to mt or to the other. Cells of the imp-1 strain agglutinate well with mt - gametes and active agglutination continues for up to 48 hours, but cell fusion occurs only very rarely. Analysis of these rare zygotes indicates that imp-1 is closely linked to the mt + locus, and fine-structural studies reveal that imp-1gametes produce a mutant mating structure involved in zygotic cell fusion. The development of sexuality in C. reinhardi therefore appears amenable to genetic dissection.
CHROMOSOME STUDIES IN WILD POPULATIONS OF D. MELANOGASTER
Authors: Stalker Harrison D 
Published: April 2021

ABSTRACT
Chromosome studies of wild D. melanogaster populations from Missouri, Mississippi, Louisiana and Texas uncovered 58 inversions. Six were common and cosmopolitan; 52 were new, rare and generally endemic. In one of two Missouri populations tested, structurally heterozygous females carried significantly more sperm at capture than did the homozygotes. In both populations comparisons of wild sperms with the females carrying them indicated significant positive assortative mating and an excess production of homozygotes among the F1 progeny. Wild females structurally heterozygous in up to three major autosomal arms showed no associated nondisjunctional egg lethality; those heterozygous in all four arms produced from 0% to 24% dead eggs, suggesting the presence of intrapopulational gene modifiers of meiosis. Texas populations supported on windfall citrus fruit showed a slight but significant difference in inversion frequencies between flies breeding on oranges and those breeding on grapefruit. Within these populations inversions were not distributed at random among individuals; rather there was an observed excess of individuals carrying intermediate numbers, and a deficiency of those carrying very few or very many inversions. While there was no significant linkage disequilibrium associated with this central tendency, there was a significant interchromosomal interaction: flies carrying inversions in chromosome 2 tended not to carry them in chromosome 3, and vice versa.
MUTANTS OF SACCHAROMYCES CEREVISIAE RESISTANT TO THE α MATING-TYPE FACTOR
Authors: Manney Thomas R , Woods Verna 
Published: April 2021

ABSTRACT
Mutants that are resistant to α-factor have been isolated from a mating-type haploid strains of yeast by direct selection on agar medium containing partially purified α-factor. All resistant mutants isolated were found to be sterile. They were characterized and compared with mutants previously isolated as nonmating. Among 93 able to mate at low frequency and to sporulate, none showed linkage to the mating-type locus. The results support the hypothesis that the response to α-factor by cells of mating-type a is essential for mating.
SELECTION IN REFERENCE TO BIOLOGICAL GROUPS. VI. USE OF EXTREME FORMS OF NONRANDOM GROUPS TO INCREASE SELECTION EFFICIENCY
Authors: Griffing B 
Published: April 2021

ABSTRACT
The strategy of using non-random groups to increase the efficiency of truncation selection is discussed. The present study, which considers extreme forms of non-random groups, complements a previous study involving full-sib groups. It is shown that of the two kinds of non-randomness, i.e. that due to homozygosity or that due to homogeneity (as represented by cloning), the latter is the most effective. This suggests that with those plant crops in which intense competition among plants exists, use of clonal propagation to produce non-random groups should be investigated.
ALCOHOL DEHYDROGENASE-NEGATIVE MUTANTS IN DROSOPHILA: DEFECTS AT THE STRUCTURAL LOCUS?
Authors: Schwartz Marcia , Sofer William 
Published: April 2021

ABSTRACT
Sixteen Adh-negative mutants (induced by ethyl methanesulfonate) were examined for the presence of inactive alcohol dehydrogenase (ADH) protein. Four techniques were utilized in an effort to detect this protein: hybrid enzyme formation, intra-cistronic complementation, sodium dodecyl sulfate electrophoresis and antibody precipitation. Eleven of the sixteen negative strains showed evidence of inactive ADH protein and are presumably mutations in the structural element. These results are discussed in light of some recent models of gene organization in higher organisms.
NEW MAP LOCATION OF ilvO IN ESCHERICHIA COLI
Authors: Cohen Bruce M , Jones Elizabeth W 
Published: April 2021

ABSTRACT
Mutations in ilvO, the operator site for operon A of the ilv region of E. coli K-12, are reported to cause a cis dominant derepression of the operon A gene products and to map between ilvC and ilvA. Studies reported here demonstrate that the F25 episome which does not carry the region between ilvC and ilvAbut only ilvE, ilvD and a part of ilvA, can transfer ilvO genetic material. Also, genes of operon A on the F25 episome respond normally to a derepression signal. It is proposed that ilvO is on the F25 episome. Five-point crosses demonstrate that mutations in ilvOmap nearer to ilvE than to ilvA. Considering this and other evidence, it is proposed that the gene order in the ilv region is CADEO, not COADE, with transcription and translation in operon A being from ilvE to ilvA not ilvA to ilvE. It is confirmed that mutations in ilvO cause a cis dominant derepression of the operon A gene products but it is also noted that mutations in ilvO lead to the appearance of an AHAS activity more resistant to inhibition by valine than that of the present O+ strain.
MATING-TYPE MUTATIONS IN SCHIZOSACCHAROMYCES POMBE: ISOLATION OF MUTANTS AND ANALYSIS OF STRAINS WITH AN h
- or h
+ PHENOTYPE
Authors: Meade James H , Gutz Herbert 
Published: April 2021

ABSTRACT
Mutants defective in various steps of the sexual cycle have been isolated from homothallic strains of Schizosaccharomyces pombe by Bresch, Müller and Egel (1968). These mutants include heterothallic h + and h - strains. We have isolated additional h + and h -mutants from homothallic strains. Those mutants which are due to mutations in the mating-type region were analyzed in detail. Our results show that the mating-type gene mat2 not only has a function in copulation and meiosis, but that it also regulates the formation of the map1 gene product (map1 is a mating-type auxiliary gene). Some of the h - mutants have lost only one of the three functions while others are defective in at least two, and perhaps all three, functions. Further, we show that the mat1 - allele of h90 strains can mutate to mat1 + but that mutations in mat2 appear to affect the mutational behavior of mat1. Finally, we describe a new inactive mating-type allele, mat2*, which is different from mat2 0 in that it can mutate to mat2 +.
GENETIC ANALYSIS OF SUSCEPTIBILITY TO ISONIAZID-INDUCED SEIZURES IN MICE
Authors: Taylor Benjamin A 
Published: April 2021

ABSTRACT
Four sets of recombinant inbred lines of mice have been used to analyze genetic differences in acute toxicity of the drug, isonicotinic acid hydrazide. Standard inbred strains, their F1 hybrids and recombinant inbred strains were all challenged with a single dose of the drug. The percent mortality of the different groups was analyzed to estimate heritability and the number of genes affecting resistance. The data indicated that resistance factors were dominant, heritability was moderate (.25-.37), and more than one gene was involved in each of four different sets of recombinant inbred lines. Possible approaches for identifying and mapping individual genes affecting resistance are discussed.
MUTATIONS AFFECTING CELL DIVISION IN TETRAHYMENA PYRIFORMIS. I. SELECTION AND GENETIC ANALYSIS
Authors: Frankel Joseph , Jenkins Leslie M , Doerder F Paul , Nelsen E Marlo 
Published: April 2021

ABSTRACT
Fourteen nitrosoguanidine-induced mutations that bring about temperature-sensitive morphological abnormalities resulting from a specific effect on cell division have been isolated as heterozygous phenotypic assortants in Tetrahymena pyriformis syngen 1. Genetic analysis revealed all to be single-gene recessives. Detailed analysis of the kinetics of assortment for one of the mutated alleles revealed a rate (0.0104 pure lines per fission) consistent with that previously observed at other loci in this organism. The mutations fall into six complementation groups (mo1, mo2, mo3, mo6, mo8, and mo12). Homozygotes of mo2 are unconditionally expressed, while all alleles of mo1, mo6, mo8, and mo12 are heat sensitive for division arrest. At the mo3 locus two alleles are heat sensitive, one is primarily cold sensitive, while two are sensitive to both heat and cold. Two out of three combinations of different mo3alleles show conventional Mendelian segregation of conditions of expression. Different alleles of mo1, mo3, mo8, and mo12 also manifest differences in penetrance at the restrictive temperature. Despite these differences involving expression, the abnormal phenotypes themselves are locus-specific and distinctive; in the one case (mo1a and mo1b) in which two alleles manifest somewhat different phenotypes, the F1 between them is intermediate. One additional recessive mutation (fat1) brings about a nonconditional lengthening of the cell cycle, with some arrest of cell division at the restrictive temperature. These findings demonstrate that selection of heterozygotes undergoing phenotypic assortment can be an effective method for obtaining substantial numbers of a desired class of temperature-sensitive mutations in T. pyriformis.
POLYMORPHISM IN A CYCLIC PARTHENOGENETIC SPECIES: SIMOCEPHALUS SERRULATUS
Authors: Smith M Yao , Fraser Alex 
Published: April 2021

ABSTRACT
A survey of sixteen isozyme loci using electrophoretic techniques was conducted for three isolated natural populations and one laboratory population of the cyclic parthenogenetic species, Simocephalus serrulatus. The proportion of polymorphic loci (33%-60%) and the average number of heterozygous loci per individual (6%-23%) in the three natural populations were found to be comparable to those found in most sexually reproducing organisms. Detailed analyses were made for one of these populations using five polymorphic loci. The results indicated that (1) seasonal changes in genotypic frequencies took place, (2) apomictic parthenogenesis does not lead to genetic homogeneity, and (3) marked gametic disequilibrium at these five loci was present in the population, indicating that selection acted on coadapted groups of genes.
SOME GENETIC CONSEQUENCES OF CHANGES IN THE LEVEL OF recA GENE FUNCTION IN ESCHERICHIA COLI K-12
Authors: Lloyd Robert G , Low Brooks 
Published: April 2021

ABSTRACT
Genetic recombination was studied in E. coli mutants that carry lesions in the recA gene but retain some capacity for generating recombinant progeny. We observed that recombination was detectable only at a very low level during the incubation of leaky RecA- merozygotes in broth. However, recombination appeared to occur at much higher frequencies when recombinant progeny were assayed by selection on minimal agar. Analysis of the recombinants obtained with Hfr donors revealed a deficiency of multiple exchanges per unit length of DNA in leaky RecA- strains. In many of these crosses recombinants that inherited donor alleles close to the transfer origin were much reduced in frequency, except when the recipient was also RecB-.
A SEX-SPECIFIC, TEMPERATURE-SENSITIVE MATERNAL EFFECT OF THE DAUGHTERLESS MUTATION OF DROSOPHILA MELANOGASTER
Authors: Cline Thomas W 
Published: April 2021

ABSTRACT
Every aspect of the phenotype of the daughterless (2-41.5) maternal effect mutation was found to be strongly temperature sensitive. Above 22°, da/da mothers produced no daughters; however female progeny did survive the da maternal effect if the last 60 hours of oogenesis and the first three hours of embryonic development took place at 18°. The females which survived under these conditions displayed morphological abnormalities in a variety of adult cuticular structures, characteristic of cell death during development. In contrast, their male siblings were morphologically normal. Upon prolonged exposure to 29°, da/da females became sterile but continued to lay eggs. Some sexually mosaic progeny from da/da mothers survived even at 25°, but the distribution and development of the female tissue in these mosaics were abnormal. It is suggested that there are multiple functions of the da + gene during oogenesis, one of which may be required specifically for the subsequent survival of female cells throughout the embryo. In addition to and distinct from its effect during oogenesis, the da mutation acted in both sexes of progeny as a recessive temperature-sensitive lethal mutation with a TSP during the first half of embryonic development.
GENETICS OF CORTISONE-INDUCED CLEFT PALATE IN THE MOUSE—EMBRYONIC AND MATERNAL EFFECTS
Authors: Biddle F G , Fraser F C 
Published: April 2021

ABSTRACT
Differences between mouse strains in frequency of embryonic, cortisone-induced cleft palate were examined. Probit analysis demonstrated a family of linear and parallel dose-response curves for different inbred and hybrid embryos. Since the differences between genotypes were not in the slopes of the response curves but rather in their location, it is proposed that the median effective dose (ED50) of cortisone required to induce cleft palate (or the tolerance) provides a more appropriate definition of the response trait and its difference than a frequency statement. The tolerance of C57BL/6J is dominant to that of A/J. A maternal effect of A/J relative to C57BL/6J dams caused a two-fold reduction in the embryonic tolerance of cortisone. Cortisone-induced cleft palate and mortality were separate response traits.—In these and previous studies on cortisone- and other glucocorticoid-induced cleft palate in the mouse, the nature of the cleft-palate-response curve appeared to be the same for all glucocorticoids, and within-strain differences in tolerance could be used as measures of potency or bioassays for a particular effect of the glucocorticoids.
A GENETIC FINE STRUCTURE ANALYSIS OF THE SUPPRESSOR 3 LOCUS IN SACCHAROMYCES
Authors: Rothstein Rodney J 
Published: April 2021

ABSTRACT
A meiotic fine structure map of a yeast tyrosine-inserting ochre suppressor, SUP3-o, was constructed. This was accomplished by examining ten intragenic suppressor-inactive revertants for their relationship to each other and to the original SUP3-o mutation. The second-site revertants map on both sides of the SUP3-o mutation. The meiotic map length based on the summation of short intervals is 45+/105 asci.
LINKAGE OF GENETIC DETERMINANTS FOR MOUSE β-GALACTOSIDASE ELECTROPHORESIS AND ACTIVITY
Authors: Breen Gail A M , Lusis Aldons J , Paigen Kenneth 
Published: April 2021

ABSTRACT
An electrophoretic polymorphism for β-galactosidase has been identified among common inbred strains of mice. It is inherited as a single Mendelian factor with two alleles showing codominant expression. This structural gene, Bge, is closely linked (0/163 recombinants) with the Bgs site on chromosome 9 which regulates systemic levels of β-galactosidase. The distribution of electrophoretic and activity phenotypes among inbred strains is not concordant, indicating that they result from separate mutations. Three aspects of β-galactosidase realization, its structure, systemic regulation and developmental program, are now known to be organized in close proximity on chromosome 9. Considered in conjunction with evidence from other mammalian systems, this suggests that the mammalian genome, like Drosophila, is organized into large functional units in which relevant regulatory and developmental information is closely associated with individual structural genes.
CORTISONE-INDUCED CLEFT PALATE IN THE MOUSE. A SEARCH FOR THE GENETIC CONTROL OF THE EMBRYONIC RESPONSE TRAIT
Authors: Biddle F G , Fraser F C 
Published: April 2021

ABSTRACT
The cause of the difference in the mean tolerance (ED50) to cortisone-induced cleft palate between the embryos of the A/J and C57BL/6J strains appears to be due to a small number of genes. A single major gene effect and a polygenic model, in the sense of many equal and additive genes, have been ruled out. The embryonic tolerance of C57BL/6J is greater than and dominant to that of A/J; two or three loci, possibly with independent effects, appear to explain the variability. A component of the variation in embryonic response may be associated with or linked to the major histocompatibility locus (H-2). No evidence was found to support the hypothesis of X-chromosome linked susceptibility to cortisone-induced cleft palate.
THE EFFECT OF A SELECTED LOCUS ON LINKED NEUTRAL LOCI
Authors: Thomson Glenys 
Published: April 2021

ABSTRACT
The effects produced on linked neutral loci as a selected locus evolves towards its equilibrium value are considered. Significant effects on the neutral loci arise if the recombination fraction between the neutral and selected loci is smaller than the order of magnitude of the selective differences at the selected locus. The effect on gene frequencies at the neutral loci, that is, the hitchhiking effect, is determined, as well as the linkage disequilibrium generated by this hitchhiking effect. One of the more important findings is that significant disequilibrium can be generated between two neutral loci by the evolution of a linked selected locus. Consideration is given to the problem of determining how the effect of selection operating in natural populations can be detected, the question of the establishment of inversions in populations, and also to the nonequilibrium properties of populations.