bluuebunny/crossref_metadata_2025_split huggingface dataset:
SEX AND THE SINGLE CELL. I. ON THE ACTION OF MAJOR LOCI AFFECTING SEX DETERMINATION IN DROSOPHILA MELANOGASTER
Authors: Baker Bruce S , Ridge Kimberly A 
Published: April 2021

ABSTRACT
Sex determination in Drosophila melanogaster is under the control of the X chrom0some:autosome ratio and at least four major regulatory genes: transformer (tra), transformer-2 (tra-2), doublesex (dsx) and intersex (ix) . Attention is focused here on the roles of these four loci in sex determination. By examining the sexual phenotype of clones of homozygous mutant cells produced by mitotic recombination in flies heterozygous for a given recessive sex-determination mutant, we have shown that the tra, tra-2 and dsx loci determine sex in a cell-autonomous manner. The effect of removing the wild-type allele of each locus (by mitotic recombination) at a number of times during development has been used to determine when the wild-type alleles of the tra, tra-2 and dsx loci have been transcribed sufficiently to support normal sexual development. The wild-type alleles of all three loci are needed into the early pupal period for normal sex determination in the cells that produce the sexually dimorphic (in pigmentation) cuticle of the fifth and sixth dorsal abdominal segments. tra+ and tra-2+ cease being needed shortly before the termination of cell division in the abdomen, whereas dsx+ is required at least until the end of division. By contrast, in the foreleg, the wild-type alleles of tra+ and tra-2 + have functioned sufficiently for normal sexual differentiation to occur by about 24 to 48 hours before pupariation, but dsx+ is required in the foreleg at least until pupariation—A comparison of the phenotypes produced in mutant/deficiency and homozygous mutant-bearing flies shows that dsx, tra-2 and tra mutants result jn a loss of wild-type function and probably represent null alleles at these genes.—All passible homozygous doublemutant combinations of ix, tra-2 and dsx have been constructed and reveal a clear pattern of epistasis: dsx &gt; tra, tra-2 &gt; ix. We conclude that these genes function in a single pathway that determines sex. The data suggest that these mutants are major regulatory loci that control the batteries of genes necessary for the development of many, and perhaps all, secondary sexual characteristics.—The striking similarities between the properties of these loci and those of the homeotic loci that determine segmental and subsegmental specialization during development suggest that the basic mechanisms of regulation are the same in the two situations. The phenotypes and interactions of these sex-determination mutants provide the basis for the model of how the wild-type alleles of these loci act together to effect normal sex determination. Implications of these observations for the function of other homeotic loci are discussed.
EXPERIMENTAL AND THEORETICAL ANALYSIS OF THE "SEX-RATIO" POLYMORPHISM IN DROSOPHILA PSEUDOOBSCURA
Authors: Curtsinger James W , Feldman Marcus W 
Published: April 2021

ABSTRACT
The Sex-ratio chromosome (SR) is a widespread, multiply inverted rearrangement of the X chromosome present in several species of Drosophila. Male carriers transmit mostly X-bearing sperm. In the absence ofstrong counteracting selection, SR is expected to increase rapidly to fixation, causing extinction. The present study incorporates a selection-components analysis of SR in laboratory populations, using the closely linked Esterase-5 locus as a marker. Estimated fitnesses show directional viability selection against SR in both males and females, heterosis for fertility and no significant effects on virility, the male adult component of fitness. Estimated fitnesses satisfy conditions for protected polymorphism and accurately predict gene-frequency trajectories in experimental populations. A model of SR gene-frequency evolution is developed, which incorporates sex-linkage, meiotic drive, viability, fertility and virility selecton. We show that conditions for protected polymorphisms are not unduly restrictive and that differential fitness among males is not sufficient for protected polymorphism, irrespective of the degree ofmeiotic drive.
STRUCTURAL ANALYSIS OF THE dur LOCI IN S. CEREVISIAE: TWO DOMAINS OF A SINGLE MULTIFUNCTIONAL GENE
Authors: Cooper Terrance G , Lam Christine , Turoscy Vanessa 
Published: April 2021

ABSTRACT
In Saccharomyces cerevisiae, the degradation of urea to carbon dioxide and ammonia is catalyzed byurea carboxylase and albphanate hydrolase. The loci coding for these enzymes (dur1 and dur2) are very tightly linked an the right arm of chromosome II between pet11 and met8. Pleiotropic mutations that fail to complement mutations in either of the dur loci were found to be predominantly located in or near the dur2 locus. We interpret these data as suggesting that the two dur loci might in reality be domains of a single gene that codes fora multifunctional polypeptide. In view OIthis conclusion, we have renamed the dur loci as the durl,2 locus.
PREFERENTIAL OCCURRENCE OF NONSISTER SPORES IN TWO-SPORED ASCI OF SACCHAROMYCES CEREVISIAE: EVIDENCE FOR REGULATION OF SPORE-WALL FORMATION BY THE SPINDLE POLE BODY
Authors: Davidow Lance S , Goetsch Loretta , Byers Breck 
Published: April 2021

ABSTRACT
Yeast cells subjected to a reversible thermal arrest of meiosis yielded progressively fewer spores per ascus as the arrest was extended. Dissection of two-spored asci by a newly developed method that prevents selection of false asci revealed that the spores were not a random sample of the haploid meiotic products. Most, if not all, pairs of spores contain nonsister products of the reductional division. Electron microscopic examination of the meiotic cells revealed the cytological basis for this bias. All four spindle pole bodies (SPBs) present at the second meiotic division normally gain a structural modification (the outer plaque) upon which the initiation of the prospore wall occurs. In the formation of a two-spored ascus, only one spindle pole body on each meiosis I1 spindle was so modified. These observations suggest that the morphogenesis of spcires is regulated at meiosis 11 by limiting the number of SPBs gaining the outer plaque. The enhancement of spore yield upon addition of fresh medium suggests that this morphogenetic regulation responds more directly to nutrient deprivation arising during the thermal arrest, rather than to elevated temperature per se.
CHROMOSOMAL SITES NECESSARY FOR NORMAL LEVELS OF MEIOTIC RECOMBINATION IN DROSOPHILA MELANOGASTER. I. EVIDENCE FOR AND MAPPING OF THE SITES
Authors: Hawley R Scott 
Published: April 2021

ABSTRACT
Meiotic exchange was measured in females heterozygous for a normal sequence X chromosome and for each of eleven T(1;4)s and each of sixteen T(1;Y)s. The results indicate that the X chromosome can be divided into five intervals, such that heterozygosity for a breakFoint in one interval strongly suppresses exchange within that interval, but has little or no effect on exchange in other intervals. The boundaries between these intervals are identified and mapped to regions 3C4-6/7, 7A-7E, 11Aand proximal to 18Con the standard salivary map; each boundary is located at (or within a small region containing) a major constriction (i.e., a block of intercalary heterochromatin) .αExchange was examined in females heterozygous for translocations broken within the constriction at IIA.The results imply that a boundary occupies only a subregion of the entire constriction and issubdivisible by translocation breakpoints. Several other properties of boundaries have been elucidated. Finally, the relationship of these data to a simple model of meiotic pairing proposed by I. SANDLER(1956)and to the role of intercalary heterochromatin in the meiotic process is discussed.
GENETIC ANALYSIS OF AUDIOGENIC SEIZURE SUSCEPTIBILITY IN C57BL/6J x DBA/2J RECOMBINANT INBRED STRAINS OF MICE
Authors: Seyfried Thomas N , Yu Robert K , Glaser Gilbert H 
Published: April 2021

ABSTRACT
The inheritance of susceptibility to audiogenic seizures (ASS) was studied in the C57BW6J (B6) and DBA/2j (D2) progenitor strains, their reciprocal F1 hybrids, backcross generations and in 21 B6 × D2 recombinant inbred (RI) strams of mice at 21 days of age. All of the D2 mice tested experienced ASS, whereas none of the B6 mice responded to the sound. Although 23% of the F1 mice experienced wild running, they were generally as resistant to ASS as their B6 parents. Mice of the F1 × B6 backcross generation were also resistant to ASS. In the F1 × D2 backcross generation, however, a significant pre-ponderance (72%) of AS-susceptible mice was found. No significant association was observed between any of the four coat-color phenotypes that were segregating in this generation and susceptibility to ASS. A continuous distribution of mean seizure severity scores and several new audiogenic response phenotypes, distinctly different from the phenotypes of either progenitor strain, were found among the 21 RI strains. These and the results from the F1 × D2 backcross generation suggest that the difference in AS susceptibility between 21-day-old B6 and D2 mice cannot be under the control of a single locus. In addition, no association was found between AS susceptibility and the chromosome 4 markers Lyb-2, Mup-1 and b among the 21 RI strains. An association was observed, however, between AS susceptibility and the Ah locus. Several of the RI strains that were AS resistant at 21 days of age became AS susceptible as adults. One RI strain was susceptible to ASS at both young and adult ages. The B6, D2 and F, mice were completely resistant to ASS at adult ages. Genetic differences were found among the RI strains for the incidence, onset, duration, and type of severity of ASS. A remarkable amount of phenotypic variability in the audiogenic response, which can be attributed only to the influence of environmental factors, occurred within several of the RI strains. A multiple-factor mode of inheritance involving a physiological threshold can account for our observations.
THE THEORY OF SPECIATION VIA THE FOUNDER PRINCIPLE
Authors: Templeton Alan R 
Published: April 2021

ABSTRACT
The founder principle has been used to explain many instances of rapid speciation. Advances from theoretical population genetics are incorporated into MAYR'S original founder-effect genetic-revolution model to yield a newer model called the genetic transilience. The basic theoretical edifice lies upon the fact that founder event can sometimes lead to an accumulation of inbreeding and an induction of gametic disequilibrium. This, in turn, causes alleles to be selected more for their homozygous fitness effects and for their effects on a more stable genetic background. Selection occurring in multi-locus systems controlling integrated developmental, physiological, behavioral, etc., traits is particularly sensitive to these founder effects. If sufficient genetic variability exists in the founder population, such multilocus genetic systems can respond to drift and the altered selective forces by undergoing a rapid shift to a new adaptive peak known as the genetic transilience. A genetic transilience is, therefore, most likely to occur when the founder event causes a rapid accumulation of inbreeding without a severe reduction in genetic variability. The implications of this model are then examined for three aspects of the founder-effect genetic-transilience model: the attributes of the ancestral population, the nature of the sampling process used t o generate the founders and the attributes of the founder population. The model is used to explain several features of the evolution of the Hawaiian Drosophila, and experimental designs are outlined to test the major predictions of the theory. Hence, this theory of speciation can be tested in the laboratory, using systems and techniques that already exist—a rare attribute of most models of speciation.
ALCOHOL DEHYDROGENASE IN THE DIPLOID PLANT STEPHANOMERIA EXIGUA (COMPOSITAE): GENE DUPLICATION, MODE OF INHERITANCE AND LINKAGE
Authors: Roose M L , Gottlieb L D 
Published: April 2021

ABSTRACT
Study of the biochemical genetics of alcohol dehydrogenase (ADH) in the annual plant Stephanameria exigua (Compositae) revealed that the isozymes are specified by a small family of tightly linked structural genes. One set of ADH isozymes (ADH-1) was induced in roots by flooding, and was also expressed in thickened unflooded tap roots, stems, ovaries and seeds. As in other plants, the enzymes are dimeric and form homo- and heterodimers. An electrophoretic survey of ADH-1 phenotypes in two natural populations revealed seven different ADH-1 homodimers in various phenotypes having one to eight enzyme bands. Genetic anaIysis of segregations from crosses involving 59 plants showed that the ADH-1 isozymes are inherited as a single Mendelian unit, Adhl. Adhl is polymorphic for forms that specify one, two, or three different ADH-1 subunits (which combine to form homo- and heterodimers), and are expressed co-dominantly in all genotypic combinations. Staining intensity of enzymes extracted from various homozygous and heterozygous plants indicated that the different subunit types specified by Adhl are produced in approximately equal amounts. These observations suggest that Adhl is a compound locus consisting of one to several tightly linked (0 recombinants among 579 testcross progeny), coordinately expressed structural genes. The genes in the two triplications also occur in various duplicate complexes and thus could have originated via unequal crossing over. The ADH-2 isozyme found in pollen and seeds is apparently specified by a different gene, Adh2. Adhl and Adh2 are tightly linked (0 recombinants among 81 testcross progeny).
ALLOZYME FREQUENCY CHANGES ASSOCIATED WITH SELECTION FOR INCREASED GRAIN YIELD IN MAIZE (ZEA MAYS L.)
Authors: Stuber C W , Moll R H , Goodman M M , Schaffer H E , Weir B S 
Published: April 2021

ABSTRACT
Frequency changes of alleles at eight enzyme loci were monitored in four long-term maize selection experiments. The results indicate that changes in frequencies of the alleles at these loci are associated with changes due to selection for improved grain yield. The frequencies changed more than is consistent with the hyFothesis of selective neutrality. In addition, significant deviations from a random-drift model were nearly always accompanied by significant linear tiends as would result ii allozyme frequencies respond to directional selection. Evaluations of linkages aiid linkage disequilibria in the selected populations indicate that the eight enzyme loci responded independently as selection progressed.
INTERCONVERSION OF YEAST CELL TYPES BY TRANSPOSABLE GENES
Authors: Klar Amar J S 
Published: April 2021

ABSTRACT
The a and α cell types of budding yeast Saccharomyces cerevisiae are controlled by alternate alleles of the mating-type locus (MAT), MATa and MATα. The cell types can be interconverted by switching alleles of MAT. The loci HMRa and HMLα, which are loosely linked to MAT, are involved in mating-type switching. Experimental evidence for their role in MAT interconversion is presented. As a result of switching, the homothallic and heterothallic strains containing the amber and ochre mutations within the HMRa locus yield corresponding amber and ochre mutant mata loci. Similarly, the hmlα mutant strain generates mata mutant alleles. That is, specific mutations from HMRa and HMLα are transmitted to MAT. A replica of the mating-type coding information originating from these loci is transposed to MAT, where it replaces the existing information. Furthermore, "Hawthorne deletions" in strains containing hmra-ambe/ochre result in production of mata-ambedochre alleles, Therefore, genetic information for MATa resides at HMRa. The switches occur in a defined set of clonally related cells. Thus, the efficient interconversion of yeast cell types is mediated by an unidirectional transfer of genetic information between nonallelic sites in a nonrandom and programmed fashion. The results are inconsistent with the "flipflop" models, but satisfy a key prediction of the general controlling element and the specific cassette models proposed for mating-type interchange.
THE GENETICS OF DROSOPHILA SUBOBSCURA POPULATIONS. XIV. FURTHER DATA ON LINKAGE DISEQUILIBRIA
Authors: Loukas M , Krimbas C B , Morgan K 
Published: April 2021

ABSTRACT
Data coming from one natural population of D. subobscura, that of Crete, are presented in detail and examined for nonrandom associations of genes and gene arrangements. This population and four others previously studied are reanalyzed for the detection of higher than first-order interactions. Only firstorder interactions are important and statistically significant, especially those concerning genes and inversions in which these genes are included. The paucity of linkage disequilibria detected is remarkable, and we argue that it does not depend on the methods of study, rather it is genuine. We further argue that most of the disequilibria detected are probably due to mechanisms based on epistatic selection.
DEVELOPMENTAL STABILITY OF DROSOPHILA MELANOGASTER UNDER ARTIFICIAL AND NATURAL SELECTION IN CONSTANT AND FLUCTUATING ENVIRONMENTS
Authors: Bradley Brian P 
Published: April 2021

ABSTRACT
Populations of Drosophila melanogaster in constant 25λ and fluctuating 20/29λ environments showed increases in developmental stability, indicated by decreases in bilateral asymmetry of sterno-pleural chaeta number. In both environments, rates of decrease in asymmetry were greater under natural selection (control lines) than under artificial stabilizing selection. Overall mean asymmetry was greater in the fluctuating environment.—There was no evidence that decreased asymmetry was due to heterozygosity, and the decline in asymmetry was not explained by the decline in chaeta number in the lines under only natural selection. However, the decline was consistent with changes in total phenotypic variance and environmental variance.— The divergence between lines after 39 generations of selection was seen in differences in asymmetry and also in the genotype-environment interaction expressed in cross-culturing experiments.
ASSEMBLY OF THE MITOCHONDRIAL MEMBRANE SYSTEM: NUCLEAR SUPPRESSION OF A CYTOCHROME b MUTATION IN YEAST MITOCHONDRIAL DNA
Authors: Coruzzi Gloria , Tzagoloff Alexander 
Published: April 2021

ABSTRACT
In a previous study, a mitochondrial mutant expressing a specific enzymatic deficiency in co-enzyme QH2-cytochrome c reductase was described (Tzagoloff, Foury and Akai 1976). Analysis of the mitochondrially translated proteins revealed the absence in the mutant of the mitochondrial product corresponding to cytochrome b and the presence of a new low molecular weight product. The premature chain-termination mutant was used to obtain suppressor mutants with wild-type properties. One such revertant strain was analyzed genetically and biochemically. The revertant was determined to have a second mutation in a nuclear gene that is capable of partially suppressing the original mitochondrial cytochrome b mutation. Genetic data indicate that the nuclear mutation is recessive and is probably in a gene coding for a protein involved in the mitochondrial translation machinery.
THE EVOLUTION OF MULTIPLE MATING BEHAVIOR BY HONEY BEE QUEENS (APIS MELLIFERA L.)
Authors: Page Robert E 
Published: April 2021

ABSTRACT
A model is presented showing that natural selection operating at the individual level can adequately explain the evolution of multiple mating behavior by honey bee queens. Group selection need not be invoked. The fitness of a given female genotype is a function of the number of sex alleles in the population, the number of matings by an individual female and the specific parameters that determine the relationship of brood viability to individual fitness. Even though the exact relationship is not known, it is almost certainly not linear. A nonlinear relationship between worker brood viability and fitness and a significant genetic load associated with the sex-determination system in honey bees are the essential components of this model.
A NEW MAP LOCATION FOR THE ilvB LOCUS OF ESCHERICHIA COLI
Authors: Newman Thomas C , Levinthal Mark 
Published: April 2021

ABSTRACT
We isolated, in E. coli K12, new alleles of the ilvB locus, the structural gene for acetolactate synthase isoenzyme I, and showed them to map at or near the ilvB619 site. The map position of the ilvB locus was redetermined because plasmids containing the ilvC-cya portion of the chromosome did not complement mutations at the ilvB locus. Furthermore, diploids for the ilvEDAC genes formed with these plasmids in an ilvHI background facilitated the isolation of the new ilvB alleles. The ilvB locus was remapped and found to be located at 81.5 minutes, between the uhp and dnaA loci. This location was determined by two- and three-point transductional crosses, deletion mapping and complementation with newly isolated plasmids. One of the new alleles of the ilvB gene is a mu-1 insertion. When present in the donor strain, this allele interferes with the linkage of genes flanking the mu-1 insertion, as well as the linkage of genes to either side of the mu-1 insertion.
CHARACTERIZATION OF AN AUTOSOMAL RUDIMENTARY-SHAPED WING MUTATION IN DROSOPHILA MELANOGASTER THAT AFFECTS PYRIMIDINE SYNTHESIS
Authors: Lastowski Donna M , Falk D R 
Published: April 2021

ABSTRACT
A new autosomal mutation, rudimental (ral), which causes rudimentary-shaped wings in Drosophila melanogaster, has been isolated following ethyl methanesulfonate (EMS) mutagenesis. The wing phenotype of rudimental is identical to that of the X-linked rudimentary (r) mutation, which affects the first three enzymes in the pyrimidine biosynthetic pathway. The autosomal mutant maps very close to ebony (3—70.7) at 70.42 on the right arm of chromosome 3. Analysis of the enzyme activities of orotate phosphoribosyltransferase (OPRTase) and orotidylate decarboxylase (ODCase) indicates that the rala26a allele has less than wild-type activity for both enzymes. This result is discussed in light of the fact that the OPRTase and ODCase activities are part of an enzyme complex, as are the carbamyl phosphate synthetase (CPSase), aspartate transcarbamylase (ATCase) and dihydroorotase (DHOase) activities, which are encoded by the complex rudimentary locus. We suggest that rudimental is also a complex locus.
SMALL-SIZED MUTANTS OF SACCHAROMYCES CEREVISIAE
Authors: Carter Bruce L A , Sudbery Peter E 
Published: April 2021

ABSTRACT
The isolation of mutants of Saccharomyces cerevisiae that divide at approximately half the size of the wild type is described. Three mutants have been isolated in which the small size at bud initiation is due to a mutation in a single nuclear gene.
MORE SEX-DETERMINATION MUTANTS OF CAENORHABDITIS ELEGANS
Authors: Hodgkin Jonathan 
Published: April 2021

ABSTRACT
Sex determination in Caenorhabditis elegans is controlled by the X chromosome: autosome ratio, i.e. 2A;XX animals are hermaphrodite, and 2A;XO animals are male. A procedure for isolating 2A;XO animals that are transformed into hermaphrodites has been developed. Nine mutations causing this transformation have been obtained: eight are recessive, and all of these fall into a new autosomal complementation group, her-1 V. The remaining mutation (her-2) is dominant and has a genetic map location similar to that of tra-1 III. Recessive mutations of tra-1 cause the reverse transformation, transforming 2A;XX animals into males. Therefore, the her-2 mutation may result in constitutive expression of tra-1. Mutations in her-1 are without effect on XX animals, but the her-2 mutation prevents sperm production in both XX and XO animals, in addition to its effect on the sexual phenotype of XO animals. The epistatic relationships between tra and her genes are used to deduce a model for the action of these genes in controlling sex determination.