bluuebunny/crossref_metadata_2025 huggingface dataset:
POPULATION DYNAMICS OF PURINE AND PYRIMIDINE ANALOG SENSITIVE AND RESISTANT MAMMALIAN CELLS GROWN IN CULTURE1
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Authors: Morrow John
Published: January 2021

The population dynamics of purine analog resistance have been studied. Two types of reconstruction experiments were performed: cloning numbers of azaguanine resistant, BUdR resistant, and sensitive cells were plated in the presence of a large number of the opposite genotype, which were made to act as a feeder layer by inactivating them with either the appropriate analog or the reverse selective HAT medium. These experiments demonstrate that there is no significant metabolic cooperation between drug resistant and drug sensitive cells, with the exception of BUdR sensitive cells, which at high densities inhibit the cloning ability of BUdR resistant cells in the presence of the drug. Thus the purine analog resistance system can be used for obtaining quantitative data concerning such parameters as mutation and selection, while at high cell densities the pyrimidine analog system appears to be unsatisfactory.——A second series of experiments indicates that, in artificial mixtures of sensitive and resistant cells grown in standard medium, the resistant cells are at a selective disadvantage and will be reduced eventually to the frequency which is observed in wild type populations.
A HISTIDINE OPERATOR-CONSTITUTIVE MUTATION DECREASES THE FREQUENCY OF RECOMBINATION WITHIN THE HISTIDINE OPERON OF SALMONELLA TYPHIMURIUM
Authors: Savic Dragutin J
Published: January 2021

A constitutive mutation in the histidine operon in Salmonella leads to a decrease in the recombinant recovery following transduction with P22 phage. This decrease appears to be a true decrease in recombination within the histidine operon and specific to that gene region. In addition, a strain with an unlinked mutation was isolated in which an operator-constitutive mutation is lethal.
THE T6 TRANSLOCATION IN THE MOUSE: ITS USE IN TRISOMY MAPPING, CENTROMERE LOCALIZATION, AND CYTOLOGICAL IDENTIFICATION OF LINKAGE GROUP III
Authors: Eicher Eva M , Green Margaret C
Published: January 2021

The occurrence of hairless piebald mice trisomic for the chromosome segments of the T6M chromosome has shown that the LG III loci hr and s are not located on T6M. The T6 breakpoint in LG III is therefore in the position hr—s—T6. T6M must carry the gene Fkl, which is located on the far side of the T6 breakpoint from hr in LG III.—T6 reduces recombination in the hr—s region.—Trisomy for the chromosome segments of the T6M chromosome appears to severely reduce viability.—The gene hr has been shown to lie between the centromere and the T6 breakpoint. The order of loci in LG III is therefore: centromere—hr—s—T6.—Equations are given for the relation between the frequency of adjacent-2 segregation and the frequency of recovery of complementation zygotes for the case in which the translocation heterozygote can form either quadrivalent or univalent-trivalent configurations at meiosis.—Linkage Group III is carried on chromosome 14. LG VI is the other linkage group involved in T6, and is carried on chromosome 15.
CYTOLOGICAL IDENTIFICATION OF THE CHROMOSOMES INVOLVED IN SEARLE'S TRANSLOCATION AND THE LOCATION OF THE CENTROMERE IN THE X CHROMOSOME OF THE MOUSE
Authors: Eicher Eva M , Nesbitt Muriel N , Francke Uta
Published: January 2021

The autosome in Searle's X-autosome translocation has been shown to be chromosome 16. The breakpoint in chromosome 16 is slightly proximal to the middle and in the X is slightly distal to the middle.—Available evidence indicates that either Linkage Group XV or Linkage Group XIX is carried on chromosome 16.—The centromere of the X chromosome is at the spf end of the linkage group.
SOMATIC SEGREGATION, RECOMBINATION, ASYMMETRICAL DISTRIBUTION AND COMPLEMENTATION TESTS OF CYTOPLASMICALLY-INHERITED ANTIBIOTIC-RESISTANCE MITOCHONDRIAL MARKERS IN S. CEREVISIAE
Authors: Rank G H , Bech-Hansen N T
Published: January 2021

Genetic analyses of 48-hr-old zygote-daughter-colony cells from crosses between chloramphenicol and erythromycin resistance markers located in mitochondrial DNA demonstrated homoplasmons of parental and recombinant genotypes, and heteroplasmons with recombinant and/or parental genotypes. Although the heteroplasmons were unstable and the homoplasmic components could be segregated by plating on selective media, the heteroplasmic state was often maintained beyond 19 cell divisions when grown on non-selective medium. Homoplasmons of recombinant genotype from repulsion crosses were observed with a frequency of 7.2, 9.0, 11.2 and 11.4 percent; two crosses with the resistance markers in coupling had 5.4 and 11.5 percent recombinants. Under non-selective conditions, the mitochondrial marker derived from the haploid parent of a mating type predominated in zygote-daughter-cells; this asymmetrical distribution could be reversed by selective pressure for the marker transmitted with low frequency. The challenge with chloramphenicol and erythromycin of zygotes from crosses of resistance-markers in repulsion revealed that inter-mitochondrial complementation was not occurring.
LONG-TERM SELECTION RESPONSE FOR 12-DAY LITTER WEIGHT IN MICE
Authors: Eisen E J
Published: January 2021

Long-term selection for increased 12-day litter weight in two replicate lines (W2, W3) of mice resulted in an apparent selection limit at about 17 generations. Quadratic polynomial and exponential models were fitted to the data in order to estimate the plateaued response and half-life of the selection process. Using the polynomial results, the half-life estimates were 4.5 and 8.6 generations for W2 and W3, respectively. The plateaued responses were 5.1 and 5.8 g which, when expressed in phenotypic standard deviation units, became 1.1 and 1.3. The exponential model provides similar estimates. A negative association between 12-day litter weight and fitness was not considered to be an adequate explanation for the plateau since there was no decrease in fertility of the selected lines. Evidence that exhaustion of genetic variability was not the cause of the plateau came from the immediate response to reverse selection. It was proposed that the plateau may be due to a negative genetic correlation between direct and maternal genetic effects, which would be expected to occur after many generations of selection. There were positive correlated responses in both replicates for adult body weight, which was in agreement with the positive genetic correlation between preweaning and postweaning body weight. The expected positive correlated response for number born was realized in only one of the replicates.
CLONAL VARIATION IN PARAMECIUM. I. PERSISTENT UNSTABLE CLONES
Authors: Finger Irving , Heller Carol , Dilworth Linda , Allmen Carolyn Von
Published: January 2021

Clones of Paramecium of identical serotype when cultured in test tubes may differ in their ability to give rise to subclones of this serotype. Characteristically, stable clones yield progeny indistinguishable from their parents, while from unstable clones diverse subclones with new serotypes can be isolated repeatedly. Stable lines are resistant to changes in culture medium and also are unaffected by most sera. In contrast, the numbers and kinds of serotypes displayed among subclones derived from unstable lines are often affected by these same agents. Stable and unstable clones are interconvertible when the medium from individual cultures is repeatedly and frequently replaced by fresh culture fluid. This effect is very likely a result of the removal of the initial exhausted medium with any cell products rather than the addition of fresh nutrient.
GENETIC ANALYSIS OF MUTATIONS INDIRECTLY SUPPRESSING recB AND recC MUTATIONS
Authors: Templin Ann , Kushner Sidney R , Clark Alvin J
Published: January 2021

Mutations in sbcB inactivate exonuclease I and suppress the UV-sensitive, mitomycin-sensitive, recombination-deficient phenotypes associated with recB and recC mutations. Mapping experiments have located sbcB about 0.4 minutes from the his operon at 38.0 on the standard map of E. coli. This places sbcB between supD and his. A four-point cross shows that sbcB lies between P2 attH and his. P2 eduction deleting the his operon beginning with P2 attH also deletes sbcB and produces the expected exonuclease I deficiency and suppression of recB  -. The occurrence of chemical-mutagen-induced and spontaneous mutations indirectly suppressing recB  - and recC  - is examined. Three lines of strains produce only sbcA mutations while only sbcB mutations occur in a fourth line. Explanations for this behavior are proposed in light of the ability of the first three lines to express sbcB mutations which they inherit by transduction.
NUCLEIC ACID HYBRIDIZATION STUDIES WITHIN THE GENUS CUCURBITA
Authors: Goldberg Robert B , Bemis William P , Siegel Albert
Published: January 2021

The DNAs of Cucurbita species were examined by several methods. All Cucurbita DNAs have a similar CsCl isopycnic banding pattern consisting of a major band at 1.695 g/cc and a well separated satellite band at 1.707 g/cc. Compared to other plant and animal genera, Cucurbita species have a large genomic proportion of rDNA; this value ranging from 1.4% to 3.1%. The genomic proportion of rDNA was found not to be useful as a characteristic indicating degree of relatedness of the various Cucurbita species. However, Cucurbita DNAs can be distinguished by the extent to which their repetitive sequences cross-hybridize to each other and an assessment of species relationships can be made on this basis.
THE RELATIVE INFLUENCE OF SEX OF PROGENY ON THE LETHAL EXPRESSION OF THE SONLESS GENE IN DROSOPHILA MELANOGASTER
Authors: Colaianne James J , Bell A E
Published: January 2021

The sex-linked maternally influenced lethal gene, sonless (snl), in D. melanogaster was shown to affect the survival of daughters as well as sons of snl/snl mothers but to a lesser degree. Interaction studies of sonless with the sex altering mutants transformer (tra) and doublesex (dsx) revealed that any alteration toward increased masculinity of progeny from snl/snl females reduced their zygotic viability, independent of snl dosage or Y chromosome presence or absence. Possible implications of these results are discussed and the original gene action hypothesis for snl is extended to incorporate these new findings.—Sonless is non-allelic but closely linked to rudimentary (r) and fused (fu), two mutants with similar sex-ratio patterns.
ENZYME EVOLUTION: I. THE IMPORTANCE OF UNTRANSLATABLE INTERMEDIATES
Authors: Koch Arthur L
Published: January 2021

The proportion of two allelic mutant forms of a haploid species can be calculated from six quantities, the original proportion, the two effective growth rate constants, the two mutation rate constants for the transition from one to the other, and the elapsed time. With a program for carrying out this calculation in a mini-computer, we set about investigating the rates of exploration of multiple intragene changes in populations of enormous numbers over a large number of cell generations. It seemed evident from the outset that unless in the past very different proportions of the different types of mutational changes occurred, then neither the numbers nor the times could have been of sufficient magnitude to account for enzyme evolution by multiple simultaneous changes within a gene to yield a superior protein. Rather, we propose that the more rapid path of enzyme evolution consisted of the sequence: 1) gene duplication, 2) inactivation of a gene copy by a chain-terminating mutation or other mutational change which suppresses transcription and/or translation, 3) multiple base-pair changes and/or small deletions and additions within the non-functioning gene, and finally, 4) reversion of the mutation which was suppressing translation. It is shown that this path will lead to faster advance, if the selective advantages of different forms are dependent on the function of the gene products at certain times in history, while at other times, although this function may be necessary, it is not limiting for growth.
MUTATION RATE AND DOMINANCE OF GENES AFFECTING VIABILITY IN DROSOPHILA MELANOGASTER
Authors: Mukai Terumi , Chigusa Sadao I , Mettler L E , Crow James F
Published: January 2021

Spontaneous mutations were allowed to accumulate in a second chromosome that was transmitted only through heterozygous males for 40 generations. At 10-generation intervals the chromosomes were assayed for homozygous effects of the accumulated mutants. From the regression of homozygous viability on the number of generations of mutant accumulation and from the increase in genetic variance between replicate chromosomes it is possible to estimate the mutation rate and average effect of the individual mutants. Lethal mutations arose at a rate of 0.0060 per chromosome per generation. The mutants having small effects on viability are estimated to arise with a frequency at least 10 times as high as lethals, more likely 20 times as high, and possibly many more times as high if there is a large class of very nearly neutral mutations.—The dominance of such mutants was measured for chromosomes extracted from a natural population. This was determined from the regression of heterozygous viability on that of the sum of the two constituent homozygotes. The average dominance for minor viability genes in an equilibrium population was estimated to be 0.21. This is lower than the value for new mutants, as expected since those with the greatest heterozygous effect are most quickly eliminated from the population. That these mutants have a disproportionately large heterozygous effect on total fitness (as well as on the viability component thereof) is shown by the low ratio of the genetic load in equilibrium homozygotes to that of new mutant homozygotes.
DIRECT INDUCTION IN WILD-TYPE NEUROSPORA CRASSA OF MUTANTS (qa-1C) CONSTITUTIVE FOR THE CATABOLISM OF QUINATE AND SHIKIMATE
Authors: Partridge C W H , Case Mary E , Giles Norman H
Published: January 2021

A color test has been developed for the selection and identification of mutants in Neurospora crassa, constitutive for the three normally inducible enzymes which convert quinate to protocatechuate. By this means seven such mutants have been recovered after ultra violet irradiation of wild type and have been shown to be allelic (or very closely linked) to the qa-1C mutants previously obtained by other means. Thus, the regulation of the synthesis of these three catabolic enzymes is indicated to be under the control of a single gene, qa-1+.
CHARACTERIZATION OF THE DNA IN DROSOPHILA MELANOGASTER
Authors: Travaglini E C , Petrovic J , Schultz J
Published: January 2021

DNA has been quantitatively extracted from Drosophila melanogaster at various stages of embryonic development and analyzed by isopycnic centrifugation in CsCl and by fractionation on methylated albumin columns. The DNA is composed of three main classes of DNA, as defined by their buoyant density, ρ, in CsCl: a bulk DNA, ρ = 1.699 g cm-3, and two satellite DNAs, ρ = 1.685 g cm-3 and ρ = 1.669 g cm-3. These three types of DNA persist throughout the development of the insect. In the unfertilized egg, 80% of the total DNA consists of the satellite DNAs; this amount decreases to 18% during the first three hours after fertilization and then remains constant through embryogenesis. There is a concomitant increase of the satellite DNA's with the bulk DNA after blastoderm formation.
THE EFFECT OF RADIATION-INDUCED MUTATIONS ON THE FITNESS OF DROSOPHILA POPULATIONS
Authors: Blaylock B G , Shugart H H
Published: January 2021

The change in frequencies of D. melanogaster and D. simulans in competition experiments was used to measure the effect of radiation on the fitness of a population. A dose of 250 or 500 rads given to the males of highly inbred lines of D. simulans at the beginning of competition and every three weeks thereafter increased the relative frequency of the irradiated population. If the dose was increased to 1000 rads, the deleterious effects of radiation became too great a burden on the population, and the frequency of the irradiated population decreased. From these results it was concluded that below certain doses the introduction of radiation-induced mutations into a highly homozygous population would increase the fitness of the population.
THE EFFECT OF SELECTION ON ESTERASE ALLOZYMES IN A BARLEY POPULATION
Authors: Allard R W , Kahler A L , Weir B S
Published: January 2021

Changes in gene and genotypic frequencies at four esterase loci were monitored over 25 generations in Composite Cross V, an experimental population of barley, to obtain experimental evidence concerning the balance of forces responsible for: (1) the marked differences in allelic frequencies among barleys from different ecogeographical regions of the world; and (2) the extensive allelic variation found within local populations of barley. Analyses of the highly significant changes in allelic frequencies which occurred in CCV showed they were due to directional selection favoring particular alleles and not to mutation, migration or genetic drift. The results show that intense balancing selection, featuring consistent excesses of heterozygotes, also occurred in CCV. It is concluded that among the factors of neo-Darwinian evolution, natural selection plays the predominant role in determining the observed patterns of allelic variation in the barley species as a whole.
STUDIES ON THE SAL LOCUS IN DROSOPHILA PSEUDOOBSCURA. II. MODES OF REGULATION OF THE SAL BANDING PATTERN
Authors: Gersh Eileen Sutton
Published: January 2021

From a consideration of genetic and chromosomal alterations which affect the banding pattern of a specific salivary chromosome region, it is concluded that (1) a regulator locus, sal, is closely linked with the region in question but separated from it spatially by a few bands; (2) either mutation of the sal locus or transfer of the region to a heterochromatic region affects the banding pattern similarly; and (3) the change probably consists of a compaction of DNA and a concomitant inactivation of genetic loci.
CHEMICAL SELECTION OF ALCOHOL DEHYDROGENASE NEGATIVE MUTANTS IN DROSOPHILA
Authors: Sofer William H , Hatkoff Mark A
Published: January 2021

We describe a selection procedure which utilizes the vapor from an unsaturated alcohol, 1-pentene-3-ol, for the detection and isolation of mutant flies with little or no alcohol dehydrogenase activity. ADH-negative flies are unaffected by exposure to the unsaturated alcohol, but ADH positives (wild-types) die after short exposure. The technique can be used to select rare ADH-negative individuals from large populations of wild-type flies.
CONGRESSION OF UNLINKED MARKERS AND GENETIC MAPPING IN THE TRANSFORMATION OF BACILLUS SUBTILIS 168
Authors: Erickson Robert J , Copeland James C
Published: January 2021

A thorough examination of cotransformation of two unlinked genetic markers in Bacillus subtilis 168 shows that the two recombinational events do not occur randomly. The cotransformation frequency is dependent on the distance between the two markers as well as on the order in which they replicate in the competent cell. These results indicate that uptake and/or integration of DNA molecules bearing these genetic markers is enhanced at the time these markers replicate in the competent cell.
RECOMBINATION AND DNA REPLICATION IN THE DROSOPHILA MELANOGASTER OOCYTE
Authors: Grell Rhoda F
Published: January 2021

A method is described that permits the recovery of a well-synchronized population of oocytes. Utilizing this pupal system, the heat-responsive period for increasing crossing-over in the Drosophila genome has been defined for the Χ chromosome and a portion of chromosome 2. The response is initiated close to the time of oocyte formation (premeiotic interphase) and is terminated after ~36 hr. During the 36-hr period different regions show characteristic responses, which vary in degree, in duration, and in initiation and termination points, so as to generate the beginning of a thermal recombination map for the Drosophila genome. Centromere regions exhibit the greatest increases in crossing-over for their respective chromosomes but are distinctly asynchronous in time; interstitial regions respond the least. Correlated autoradiographic studies have localized DNA replication in the oocyte to a ~24-hr period, which also begins close to oocyte formation (premeiotic interphase); late labeling in restricted regions, undetectable with the present method, could extend the period, as could prolonged synthesis in the oocyte. The results demonstrate that DNA replication and the heat-sensitive period for enhancement of crossing-over are coincident processes over most and possibly all of their length.
THE GENETIC SYSTEM CONTROLLING HOMOTHALLISM IN SACCHAROMYCES YEASTS
Authors: Harashima Satoshi , Nogi Yasuhisa , Oshima Yasuji
Published: January 2021

There are four types of life cycles in Saccharomyces cerevisiae and its related species. A perfect homothallic life cycle (the Ho type) is observed in the classic D strain. Two other types show semi-homothallism; one of them shows a 2-homothallic diploid:2α heterothallic haploid segregation (the Hp type) and another, a 2-homothallic:2a segregation (the Hq type). In the segregants from these Ho, Hp, and Hq diploids, each homothallic segregant shows the same segregation pattern as its parental diploid. The fourth type has a heterothallic life cycle showing a 2a:2α segregation and the diploids are produced by the fusion of two haploid cells of opposite mating types. The diploids prepared by the crosses of α Hp (an α haploid segregant from the Hp diploid) to a Hq (an a haploid from the Hq diploid) segregated two types (Type I and II) of the Ho type homothallic clone among their meiotic segregants. Genetic analyses were performed to investigate this phenomenon and the genotypes of the Ho type homothallic clones of Type I and Type II. Results of these genetic analyses have been most adequately explained by postulating three kinds of homothallic genes, each consisting of a single pair of alleles, HO/ho, HMα/hmα, and HMa/hma, respectively. One of them, the HMα locus, was proved to be loosely linked (64 stranes) to the mating-type locus. A spore having the HO hmα hma genotype gives rise to an Ho type homothallic diploid (Type I), the same as in the case of the D strain which has the HO HMα HMa genotype (Type II). A spore having the a HO hmα HMa or α HO HMα hma genotype will produce an Hp or Hq type homothallic diploid culture, respectively. The other genotypes, a HO HMα hma, α HO hmα HMa, and the genotypes combined with the ho allele give a heterothallic character to the spore culture. A possible molecular hypothesis for the mating-type differentiation with the controlling elements produced by the HMα and HMa genes is proposed.
REGULATION OF PHOSPHATE METABOLISM IN NEUROSPORA CRASSA: ISOLATION OF MUTANTS DEFICIENT IN THE REPRESSIBLE ALKALINE PHOSPHATASE
Authors: Gleason Mary K , Metzenberg Robert L
Published: January 2021

Mutants of Neurospora crassa have been isolated that lack the repressible alkaline phosphatase, but, unlike nuc-1 and nuc-2 mutants, are able to make the repressible acid phosphatase and the repressible phosphate permease under conditions of derepression (phosphate deprivation). The new mutants, called pho-2, map in Linkage Group V, and are unlinked to the putative control mutants, nuc-1, nuc-2-pconc, and pregc. Three of the pho-2 mutants do not make detectable amounts of repressible alkaline phosphatase, but the fourth makes about 1% of the level found in wild type. The small amount of alkaline phosphatase made by this strain appears to be qualitatively similar or identical to the wild-type enzyme, as judged by electrophoretic mobility, heat stability, and titration with specific antibody to the wild-type enzyme. Several revertants of this strain have been examined in the same way, and the alkaline phosphatase of these strains also appears to be qualitatively normal. Reversion events can occur at, or near, the pho-2 locus, but also occur in at least two unlinked sites (suppressor mutations). One suppressor maps very close to nuc-1.
RECONSTITUTION OF THE Rr COMPOUND ALLELE IN MAIZE
Authors: Dooner H K , Kermicle J L
Published: January 2021

The Rr:standard allele in maize, which conditions anthocyanin pigmentation in plant and seed tissues in the presence of appropriate complementary factors, is associated with a tandem duplication. The proximal member of the duplication carries P, the plant pigmenting determiner and the distal member member carries S, the seed pigmenting determiner. Derivatives from Rr that have lost S function are designated rr. They represent either losses of the distal member of the duplication (P derivatives) or mutations of S to s (P s). Derivatives that have lost P function are designated Rg, and represent either losses of the proximal member of the duplication (S derivatives) or mutations of P to p (p S).—All four possible types of rr/Rg heterozygotes were tested for their capacity to yield Rr reconstitution by crossing over. No Rr derivatives were obtained from P/S heterozygotes, a result consistent with the view that P and S occupy corresponding positions in homologous chromosome segments. Rr reconstitution was detected in both tandem duplication heterozygotes P s/S and P/p S, and was found to be about ten times more frequent in the latter. The ratio of Rr reconstitution in the two heterozygotes is a function of position of the anthocyanin marker within the duplicated segment. The data from these heterozygotes allow one to measure the distance between P and S, that is to say, the genetic length of the duplicated segment. This distance was found to be 0.16 map units. The highest frequency of Rr reconstitution was obtained from P s/p S heterozygotes, since direct pairing (see PDF) as well as the p//s type of displaced pairing have the potential to produce Rr derivatives. One of the Rg derivatives used in this study, Rg  6, was found to back-mutate in some sublines to Rr. The basis for this instability remains unknown.
GENETIC STRUCTURE OF A POPULATION OCCUPYING A CIRCULAR HABITAT
Authors: Nagylaki Thomas
Published: January 2021

The geographical structure of a finite population distributed continuously and homogeneously along a circular habit is explored. Selection is supposed to be absent, and the analysis is restricted to a single locus with discrete, non-overlapping generations. Assuming every mutant is new to the population, the rate of decay of genetic variability is obtained, and the probability that two homologous genes separated by a given distance are different alleles is calculated. If moments of the migration function higher than second are neglected, the eigenvalue equation is shown to be a simple trigonometric one, and the Fourier series giving the transient and stationary probabilities of allelism are summed in terms of elementary functions. The proportion of homozygotes, the effective number of alleles maintained in the population, and the amount of local differentiation of gene frequencies are discussed.
A MODEL FOR ANALYSIS OF POPULATION STRUCTURE
Authors: Rothman Edward D , Sing Charles F , Templeton Alan R
Published: January 2021

Arguments have been presented for the appropriateness of a multinomial Dirichlet distribution for describing single-locus genotypic frequencies in a subdivided population. This distribution is defined as a function of allele frequency, the average (over the entire population) inbreeding coefficient and the correlation between genotypes within a subdivision. Alternative parameterizations and their genetic interpretations are given.—We then show how information from a sample drawn from this subdivided population, in the absence of pedigrees, can be combined with the multinomial Dirichlet model to form a likelihood function. This likelihood function is then used as the basis for estimation and testing hypotheses concerning the genetic parameters of the model. Comparisons of this approach to the alternative procedure of COCKEXHAM (1969) and (1973) are made using human data obtained from Tecumseh, Michigan and Monte Carlo simulations.—Finally, implications of these results to statistical inference and to mutation rates are presented.
FURTHER EVIDENCE FOR SELECTIVE DIFFERENCES BETWEEN ISOALLELES IN DROSOPHILA
Authors: Wills Christopher , Phelps Julia , Ferguson Richard
Published: January 2021

A number of separate strains of Drosophila pseudoobscura were inbred for 38 generations of brother-sister mating with forced heterozygosity for two alleles of either the octanol dehydrogenase or esterase-5 locus. Crosses were set up within each of these inbred lines such that simple mendelian ratios were expected, and eggs from these crosses were placed on media with additions of simple chemicals likely to interact with alleles of the two loci—octanol and ethanol for the ODH locus and tributyrin and triacetin for the E-5 locus. Similar crosses were set up involving parental flies with normally heterozygous genetic background as a control.—Significant deviations from mendelian expectation were observed in inbred E-5 flies grown on tributyrin, inbred ODH males grown on octanol, and inbred ODH females grown on ethanol. There was also a strong effect of octanol medium on males of one of the inbred E-5 lines, and a weak effect of tributyrin medium on ODH inbred females.—The probability that these results reflect interactions between these loci and the environment is assessed in the light of differences between the present results and those obtained at earlier stages of inbreeding.
EVIDENCE FOR THE SINGLE PHASE PAIRING THEORY OF MEIOSIS
Authors: Novitski E
Published: January 2021

The segregation pattern of an attached X chromosome with several Y-autosome translocations conflicts with the expectations based on the distributive pairing hypothesis because the chromosomes segregating from the translocation configuration include both exchange and non-exchange chromosomes. The results of the second experiment involving three compound chromosomes go even further; they suggest that the essential association which determines the segregation of nonhomologous elements is in fact set up prior to the time of crossing over.
RECIPROCAL TRANSLOCATIONS AND TRANSLOCATION DISOMICS OF ASPERGILLUS AND THEIR USE FOR GENETIC MAPPING
Authors: Käfer Etta
Published: January 2021

Two new techniques are described for genetic mapping of reciprocal translocations in A. nidulans, which can be used to locate centromeres and meiotically unlinked markers. They both make use of unbalanced disomics from heterozygous translocation crosses. These are mainly hyperhaploids of two classes: either typical-looking n + 1 with a normal chromosome in addition to a haploid set containing the translocation, or translocation disomics. When large chromosome segments are involved, such disomics, as well as stable aneuploids and duplication types, show characteristic phenotypes and can be classified visually. The first method maps translocation breaks qualitatively, since translocated markers can be identified when translocation disomics are analyzed for heterozygous markers. The second method measures meiotic linkage of any marker to the translocation breaks when allele ratios in the balanced haploid sectors of either or both classes of disomics are determined: linked markers show reciprocal deviations from 1:1—In addition, it can be shown that frequencies of nondisjunction and recovery of specific translocation disomics both depend on the relative position of the break within a chromosome arm. Such information can provide a rough estimate of the positions of breaks for a new translocation.—Using these techniques, as well as mitotic mapping in homo- and heterozygous translocation diploids, four reciprocal translocations were mapped. From these results, information on the sequence and orientation of most of the "meiotic fragments" of the current maps (groups III, VI, VII and VIII) was obtained, and the position of the centromeres of groups VI and VII were identified. Translocation disomics are also used to map meiotically unlinked single genes, e.g. oliA of group VII, to specify chromosome segments.
CHEMICAL SELECTION OF MUTANTS THAT AFFECT ALCOHOL DEHYDROGENASE IN DROSOPHILA II. USE OF 1—PENTYNE—3—Ol
Authors: O'Donnell Janis , Gerace Larry , Leister Flora , Sofer William
Published: January 2021

We describe a procedure for the selection of alcohol dehydrogenase negative mutants in Drosophila. The method consists of exposing eggs and larvae to low concentrations of 1-pentyne-3-ol dissolved in the culture medium. Only those flies with greatly reduced levels of alcohol dehydrogenase activity survive. In addition, genotypically negative flies die if their mothers are alcohol dehydrogenase positive. Using this procedure and formaldehyde to generate mutants, we were able to detect seven alcohol dehydrogenase negative mutants out of 350,000 individuals subjected to selection. At least five of the mutants contain small deletions that include the alcohol dehydrogenase locus.
A NEW METHOD FOR MUTANT SELECTION IN SACCHAROMYCES CEREVISIAE
Authors: Henry Susan A , Horowitz Bernard
Published: January 2021

A new method for the selection of auxotrophic, antibiotic- and temperature-sensitive mutants in Saccharomyces cerevisiae is reported. The technique is based upon the observation that certain fatty acid auxotrophs of yeast die when deprived of fatty acid only under conditions supporting growth. When macromolecular synthesis is blocked, the fatty acid-starved cells survive. By appropriate manipulation of a fatty acid-requiring strain enrichment as great as 75-fold was achieved for certain classes of auxotrophic mutants. An enrichment of approximately 100-fold is possible for some antibiotic-sensitive mutants. Selection for temperature-sensitive mutants, however, resulted in less than a 2-fold increase in the frequency of such mutants, probably because of the heterogeneity of this mutant category. It is likely that only that fraction of temperature-sensitive mutations which rapidly and reversibly blocks macromolecular synthesis is selected by this technique.
A REVISION OF THE CYTOLOGY AND ONTOGENY OF SEVERAL DEFICIENCIES IN THE 3A1—3C6 REGION OF THE X CHROMOSOME OF DROSOPHILA MELANOGASTER
Authors: Kaufman T C , Shannon M P , Shen M W , Judd B H
Published: January 2021

The cytology and developmental attributes of 18 deficiency mutations in the 3A1-3C6 region of the salivary gland X chromosome of Drosophila melanogaster have been investigated. The cytological limits of several older deficiencies have been revised and clarified and several new deficiencies are characterized. The deficiency mutants, with one possible exception, show a lethal phase in the late embryonic period or the early first larval instar. In contrast, the earliest acting point mutation lethals exposed by these deficiencies generally exhibit a somewhat later, post-embryonic lethality, perhaps indicating that the deficiencies are having some cumulative or synergistic impact on development. However, even with this difference in time of lethality, it is still possible to conclude that it is not the absolute size of the deficiency but rather the character of the loci deleted that determines the impact on development. Observations on the morphology of lethal embryos shows that while this analysis is internally consistent, it does not agree with earlier work. None of the 3A1-3C6 deficiencies causes any major teratologies during embryogenesis. Furthermore, the "earliest acting" gene in this region does not lie in band 3C1 but is most likely associated with bands 3A8-10.
CLONAL AGE AND THE PROPORTION OF DEFECTIVE PROGENY AFTER AUTOGAMY IN PARAMECIUM AURELIA
Authors: Fukushima Shinichi
Published: January 2021

The relation of mortality and the proportion of progeny with reduced fission after autogamy to the clonal age in Paramecium aurelia was investigated. This relation is not linear but the proportion of defective progeny increases stepwise. The observations are in agreement with those expected from the calculations of the number of deleterious mutations in the micronucleus.
CROSSING OVER AND DIPLOID EGG FORMATION IN THE ELONGATE MUTANT OF MAIZE
Authors: Nel P M
Published: January 2021

Rhoades (1941) found recombination in the proximal regions of chromosome 5 to be higher in male than in female flowers. Two explanations were proposed to account for the lower female values, namely: (1) there is a basic difference in rates of crossing over in mega- and microsporocytes, or (2) selective orientation of the chromosome 5 bivalent on the meiotic spindle leads to the preferential segregation of noncrossover chromatids to the basal megaspore. These alternatives have been tested by carrying out a half-tetrad analysis of the diploid eggs produced by plants homozygous for the recessive elongate (el) allele. The A2—Bt crossover values determined from the diploid eggs of elongate plants were much lower than those calculated from haploid sperm of both El el and el el plants. Since male and female flowers should have similar cross-over values if the orientation hypothesis were correct, it was concluded that the amount of crossing over in the A2-Bt region of chromosome 5 is intrinsically higher in male than in female meiocytes. In the analysis of diploid eggs the use of the Bt locus, which marks the centric region of chromosome 5, provided information on the origin of diploid eggs. The genotypic constitution of 425 diploid eggs was ascertained. Of these, 20.4% were Bt bt. They could not be accounted for by failure of the second meiotic division or by replication during the interphase between the two meiotic divisions, but are expected if there is a single division with an equational separation of the centromere regions of chromosome 5. The Bt Bt and bt bt genotypes arise from a disjunctional separation. It is proposed that diploid eggs are produced by an abnormal meiosis in which there is one division with either disjunctional or equational separation. Disjunctional separation is more frequent but the ratio of the two types varies from ear to ear. Recombination in the A2-Bt-Pr region of chromosome 5 was found to be higher in the haploid gametes of elongate homozygotes than in El El and El el plants. On the other hand, crossing over was reduced in the Sh-Bz segment of chromosome 9 in elongate plants, but the adjacent Bz—Wx interval was unaffected.
EXPRESSION IN ORGAN CULTURE OF AGOUTI LOCUS GENES OF THE MOUSE
Authors: Knisely A S , Gasser David L , Silvers Willys K
Published: January 2021

Cleffmann (1963) reported that pigment cells of the lethal yellow (Ay/a) genotype change to black immediately upon cultivation, and continue to produce black pigment unless sulfhydryl reagents are added to the culture medium. We have attempted to repeat this observation and have not been able to do so. We also have been unable to induce the synthesis of yellow pigment by adding glutathione to cultures of agouti (A/A) skin. We therefore suggest that hypotheses which attempt to explain the action of agouti locus genes on the basis of effects of sulfhydryl compounds be considered with caution.
A GENETIC ANALYSIS OF PHOTOTACTIC BEHAVIOR IN DROSOPHILA MELANOGASTER I. SELECTION IN THE PRESENCE OF INVERSIONS
Authors: Markow Therese Ann
Published: January 2021

The effectiveness of selection for positive and negative phototactic behavior in populations of Drosophila melanogaster heterozygous for various multiple inversions was compared using the method of realized heritability. Selection in the presence of FM6, SM1 or TM3 alone was as effective as in populations carrying no inversions. However, the presence of FM6 and TM3 together reduced the effectiveness of selection for photopositive behavior and FM6 and SM1 and TM3 restricted the response to selection for negative phototactic behavior. The results are discussed in terms of the organization of genes influencing phototactic behavior in this species.
GENETIC CONTROL OF RADIATION SENSITIVITY IN SCHIZOSACCHAROMYCES POMBE
Authors: Nasim A , Smith B P
Published: January 2021

Genetic analysis of a large number of radiation-sensitive mutants of S. pombe, isolated in different laboratories, showed that these isolates represent 22 non-allelic loci. The mutants were shown to fall into three distinct classes concerning response to UV and ionizing radiation, including two mutants which are primarily sensitive to ionizing radiation but not to UV. Single-gene mutants were crossed to obtain supersensitive double mutants. Such double mutants showed a marked increase in sensitivity to a variety of inactivating agents as compared to the parental strains. The isolation of three classes of radiation-sensitive mutants and the construction of double mutants implies the presence of multiple pathways in S. pombe for repair of radiation-induced damage. The bearing of these data on cellular repair mechanisms in eukaryotes is discussed.
SEX CHROMOSOME MEIOTIC DRIVE SYSTEMS IN DROSOPHILA MELANOGASTER I. ABNORMAL SPERMATID DEVELOPMENT IN MALES WITH A HETEROCHROMATIN-DEFICIENT X CHROMOSOME (sc
4
sc
8)
Authors: Peacock W J , Miklos George L Gabor , Goodchild D J
Published: January 2021

The meiotic drive characteristics of the In(1)sc4Lsc8R/Y system have been examined by genetic analysis and by light and electron microscopy. sc4sc8/Y males show a direct correlation between nondisjunction frequency and meiotic drive. Temperature-shift experiments reveal that the temperature-sensitive period for nondisjunction is at meiosis, whereas that for meiotic drive has both meiotic and post-meiotic components. Cytological analyses in the light and electron microscopes reveal failures in spermiogenesis in the testes of sc  4  sc  8 males. The extent of abnormal spermatid development increases as nondisjunction becomes more extreme.
Resolution Status and Age as Moderators for Interpersonal Everyday Stress and Stressor-Related Affect
Authors: Witzel Dakota D , Stawski Robert S
Published: January 2021

Objectives

To examine stressor characteristics (i.e., stressor resolution) and individual differences (i.e., age) as moderators of affective reactivity and residue associated with everyday interpersonal stressors, including arguments and avoided arguments.

Method

A sample of 2,022 individuals participated in the second wave of the National Study of Daily Experiences (meanage = 56.25, range = 33–84). Over 8 consecutive evenings, participants completed the Daily Inventory of Stressful Experiences and self-report measures of stressor resolution status and daily negative affect (NA) and positive affect (PA). Using multilevel modeling, we examined whether increases in daily NA and decreases in daily PA associated with arguments and avoided arguments occurring on the same day (i.e., reactivity) or the day before (i.e., residue) differed depending on resolution of the interpersonal stressor. We further examined whether such stressor resolution effects were moderated by age.

Results

Resolution significantly dampened NA and PA reactivity and residue associated with arguments; NA reactivity associated with avoided arguments (ps < .05). Older age was associated with being more likely to resolve both arguments and avoided arguments (ps < .05) and did reduce reactivity associated with avoided arguments. Older age did not moderate PA reactivity or NA or PA residue associated with either arguments or avoided arguments (ps > .05).

Discussion

Unresolved everyday arguments and avoided arguments are differentially potent in terms of affective reactivity and residue, suggesting resolution may be crucial in emotional downregulation. Future work should focus on exploring resolution of other everyday stressors to garner a comprehensive understanding of what characteristics impact stressor–affect associations and for whom.
Coping of Older Adults in Times of COVID-19: Considerations of Temporality Among Dutch Older Adults
Authors: Verhage Miriam , Thielman Lucia , de Kock Lieke , Lindenberg Jolanda
Published: January 2021

Objectives

Globally, mitigation measures during the coronavirus disease 2019 (COVID-19) pandemic have focused on protecting older adults. Earlier disaster studies have shown the importance of including older peoples’ voices to prevent secondary stressors, yet these voices have received little attention during this pandemic. Here, we explore how Dutch older adults view this crisis and cope with measures to contribute to our understanding of coping of older adults in general and during disaster situations more specifically.

Method

Qualitative study using semistructured telephone interviews with 59 diverse older adults aged 54–95 throughout the Netherlands.

Results

Older adults typify this crisis as ungraspable, disrupting their daily and social lives. Despite filling their lives with activities, they experience loss or lack of purpose. They try to follow measures to decrease infection risk and gain control, and use problem- and emotion-focused coping strategies. Emotion-focused strategies used were interpreting their personal vulnerability, self-enhancing comparisons, acceptance, and distraction. In the latter 2 strategies, the temporary nature of measures was emphasized.

Discussion

Older adults describe this crisis consistently with earlier findings from disaster studies. They use known coping strategies, but emphasize the duration in relation to their expectation of temporality. This underscores a dynamic, processual approach toward coping that incorporates temporal dimensions such as duration and order. Our findings stress the importance of acknowledging heterogeneity among older adults and adjusting communication about mitigation measures to decrease insecurity and increase resonance. This may make COVID-19 mitigation measures more manageable and age-responsible and allow older adults to start living again.
A plasma metabolomic signature of Leber hereditary optic neuropathy showing taurine and nicotinamide deficiencies
Authors: Bocca Cinzia , Le Paih Victor , Chao de la Barca Juan Manuel , Kouassy Nzoughet Judith , Amati-Bonneau Patrizia , Blanchet Odile , Védie Benoit , Géromin Daniela , Simard Gilles , Procaccio Vincent , Bonneau Dominique , Lenaers Guy , Orssaud Christophe , Reynier Pascal
Published: January 2021

Leber’s hereditary optic neuropathy (LHON) is the most common disorder due to mitochondrial DNA mutations and complex I deficiency. It is characterized by an acute vision loss, generally in young adults, with a higher penetrance in males. How complex I dysfunction induces the peculiar LHON clinical presentation remains an unanswered question. To gain an insight into this question, we carried out a non-targeted metabolomic investigation using the plasma of 18 LHON patients, during the chronic phase of the disease, comparing them to 18 healthy controls. A total of 500 metabolites were screened of which 156 were accurately detected. A supervised Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA) highlighted a robust model for disease prediction with a Q2 (cum) of 55.5%, with a reliable performance during the permutation test (cross-validation analysis of variance, P-value = 5.02284e−05) and a good prediction of a test set (P = 0.05). This model highlighted 10 metabolites with variable importance in the projection (VIP) > 0.8. Univariate analyses revealed nine discriminating metabolites, six of which were the same as those found in the Orthogonal Projections to Latent Structures Discriminant Analysis model. In total, the 13 discriminating metabolites identified underlining dietary metabolites (nicotinamide, taurine, choline, 1-methylhistidine and hippurate), mitochondrial energetic substrates (acetoacetate, glutamate and fumarate) and purine metabolism (inosine). The decreased concentration of taurine and nicotinamide (vitamin B3) suggest interesting therapeutic targets, given their neuroprotective roles that have already been demonstrated for retinal ganglion cells. Our results show a reliable predictive metabolomic signature in the plasma of LHON patients and highlighted taurine and nicotinamide deficiencies.