bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE MANIFESTATION OF CHROMOSOME REARRANGEMENTS IN UNORDERED ASCI OF NEUROSPORA
Authors: Perkins David D 
Published: January 2021

ABSTRACT
Rapid, effective techniques have been developed for detecting and characterizing chromosome aberrations in Neurospora by visual inspection of ascospores and asci. Rearrangements that are detectable by the presence of deficient, nonblack ascospores in test crosses make up 5 to 10% of survivors after UV doses giving 10-55% survival. Over 135 rearrangements have been diagnosed by classifying unordered asci according to numbers of defective spores. (These include 15 originally identified or analyzed by other workers.) About 100 reciprocal translocations (RT's) have been confirmed and mapped genetically, involving all combinations of the seven chromosomes. Thirty-three other rearrangements generate viable nontandem duplications in meiosis. These consist of insertional translocations (IT's) (15 confirmed), and of rearrangements that involve a chromosome tip (10 translocations and 3 pericentric inversions). No inversion has been found that does not include the centromere. A reciprocal translocation was found within one population in nature. When pairs of RT's that involve the same two chromosome arms were intercrossed, viable duplications were produced if the breakpoints overlapped in such a way that pairing resembled that of insertional translocations (27 combinations).—The rapid analytical technique depends on the following. Deficiency ascospores are usually nonblack (W: "white") and inviable, while nondeficient ascospores, even those that include duplications, are black (B) and viable. Thus RT's typically produce 50% black spores, and IT's 75% black. Asci are shot spontaneously from ripe perithecia, and can be collected in large numbers as groups of eight ascospores representing unordered tetrads, which fall into five classes: 8B:0W; 6B:2W, 4B:4W, 2B:6B, 0B:8W. In isosequential crosses, 90-95% of tetrads are 8:0. When a rearrangement is heterozygous, the frequencies of tetrad classes are diagnostic of the type of rearrangement, and provide information also on the positions of break points. With RT's, 8:0 (alternate centromere segregation) = 0:8 (adjacent-1), 4:4's require interstitial crossing over in a centromere-break point interval, and no 6:2's or 2:6's are expected. With IT's, duplications are viable, 8:0 = 4:4, 6:2's are from interstitial crossing over, 0:8's or 2:6's are rare. Tetrads from RT's that involve a chromosome tip resemble those from IT's, as do tetrads from intercrosses between partially overlapping RT's that involve identical chromosome arms.—Because viable duplications and other aneuploid derivatives regularly occur among the offspring of rearrangements such as insertional translocations, care must be taken in selecting stocks, and original strains should be kept for reference.
DILUTION KINETIC STUDIES OF YEAST POPULATIONS: IN VIVO AGGREGATION OF GALACTOSE UTILIZING ENZYMES AND POSITIVE REGULATOR MOLECULES
Authors: Tsuyumu Shinji , Adams Bruce G 
Published: January 2021

ABSTRACT
By use of a selective medium containing ethidium bromide, population analyses of yeast galactose long-term adaptation mutants (gal3) in the process of deadaptation in the absence of galactose have been performed. The analysis of diploid strains homozygous for the gal3 locus but heterozygous for different combinations of the other mutant galactose loci, which thus have reduced amounts of the gene products of those loci, have demonstrated that, in addition to the two permease units determined in a previous study, a cell requires one complex of the Leloir pathway enzymes and two complexes specified by the Gal4 locus to be readily induced. From the consideration of these complexes as being aggregated molecules which are diluted out as units (i.e., if such a molecule were a dimer, it would not dissociate into monomers) during cell growth, the in vivo aggregation of these enzymes and the Gal4 gene product could be studied. The data indicate that the function of the Gal4 gene product is to activate a Leloir enzyme complex. It is postulated that the gal3 phenotype is the result of such strains' inability to actively synthesize an endogenous co-inducer which allows wild-type cells to be readily induced upon exposure to galactose
SELECTION BY FERTILITY IN DROSOPHILA PSEUDOOBSCURA
Authors: Anderson Wyatt W , Watanabe Takao K 
Published: January 2021

ABSTRACT
Fertility, the component of selection due to female fecundity and male mating success, differed significantly among the ST/ST, ST/AR, and AR/AR karyotypes in experimental populations and varied with karyotypic frequency. In relation to ST/AR, ST/ST females and males had higher fertilities at low frequency; AR/AR males and females were at a significant fertility disadvantage at intermediate frequency, while at low and at high frequencies their fertilities matched or exceeded that of the heterokaryotype. These fertility differences were comparable in size to viability differences previously reported for D. pseudoobscura karyotypes. Differential fertility seems likely to be an important element, perhaps just as important as differential viability, in the balancing selection that maintains the chromosomal polymorphism in this species.
GENETIC LOAD IN NATURAL POPULATIONS: IS IT COMPATIBLE WITH THE HYPOTHESIS THAT MANY POLYMORPHISMS ARE MAINTAINED BY NATURAL SELECTION?
Authors: Tracey Martin L , Ayala Francisco J 
Published: January 2021

ABSTRACT
Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.
SUPPRESSION OF TWO MISSENSE ALLELES OF THE TRP5 LOCUS OF SACCHAROMYCES CEREVISIAE
Authors: Singh Arjun , Manney T R 
Published: January 2021

ABSTRACT
A suppressor SUP101 of alleles trp5-67 and trp5-18 of the trp5 locus of Saccharomyces cerevisiae is described. The two suppressible mutations have been previously classified as missense. The suppression does not result from a physiological bypass of the tryptophan synthetase-catalyzed reaction, since the suppression is allele-specific. IU alleles trp5-70, tryp5-95, and trp5-102; IA alleles trp5-81, trp5-101, and trp5-103; and the ochre alleles trp5-33 and trp5-48 are not suppressed by SUP101. SUP101 does not suppress ochre alleles ade2-1, his5-2, arg4-17, lys1-1, amber alleles trp1-1, tyr7-1, or unclassified alleles at a number of other loci. These results indicate SUP101 is a missense suppressor. Growth on tryptophanless media is dependent upon gene dosage of both the suppressor and the suppressible alleles. Only the diploids homozygous both for the suppressor and suppressible alleles produce growth equivalent to growth of the haploids bearing a suppressible allele and the suppressor. Suppressor-bearing strains grow poorly even on tryptophan-supplemented media. In more than 100 asci analyzed partial growth inhibition on the complete medium always segregated with the suppressor.
MOVEMENT OF MODULATOR IN MAIZE: A TEST OF AN HYPOTHESIS
Authors: Greenblatt Irwin M 
Published: January 2021

ABSTRACT
A model of Modulator movement (Greenblatt 1968) from one chromosomal site to another requires that all movements produce potential twin mutations within the affected cell lineage. From this model the prediction would be that (1) untwinned red and untwinned light-variegated sectors within the pericarp of medium-variegated maize must occur in equal frequency even though partners become lost, during ear morphogenesis, to the final pericarp tissue, and that (2) among the backcross progeny of a homozygous PrrMp individual mated with Pwr/Pwr pollen, red offspring and light-variegated offspring would occur in equal frequency. Both expectations have been realized and herein reported.
REPAIR REPLICATION AND PHOTOREPAIR OF DNA IN LARVAE OF DROSOPHILA MELANOGASTER
Authors: Boyd James B , Presley Jack M 
Published: January 2021

ABSTRACT
Repair replication of DNA has been studied in first instar larvae of Drosophila melanogaster with isopycnic centrifugation techniques. Larvae were fed BUdR, FUdR, streptomycin, penicillin, and Fungazone for two to four hours prior to exposure to UV, X-rays, MMS, or EMS. Feeding was continued for four hours in the presence of 3HBUdR and DNA was isolated from whole larvae. Repair replication is stimulated by each of these agents. MMS is about 10 times as potent as EMS in stimulating repair synthesis. A dose of 200 ergs/mm2 largely saturates the level of repair replication observed after UV irradiation. Repair replication rises between 0 and 80,000 R of X-rays before falling off. Semiconservative synthesis is seriously inhibited above a dose of 40,000 R of X-rays. Photorepair has been detected as a reduction in repair synthesis resulting from post-irradiation exposure to photoreactivating light. The same treatment has no detectable effect on X-ray-stimulated repair replication. Repair replication is insensitive to the presence of caffeine or hydroxyurea during the final incubation, although semiconservative synthesis is strongly inhibited by these agents. A mixture of BUdR and 3HTdR can be used to replace 3HBUdR in detecting repair replication.
ANALYSIS OF THE CHROMOSOME ABERRATIONS INDUCED BY X-RAYS IN SOMATIC CELLS OF DROSOPHILA MELANOGASTER
Authors: Gatti M , Tanzarella C , Olivieri G 
Published: January 2021

ABSTRACT
A technique has been perfected for enabling good microscope preparations to be obtained from the larval ganglia of Drosophila melanogaster. This system was then tested with X-rays and an extensive series of data was obtained on the chromosome aberrations induced in the various stages of the cell cycle.—The analysis of the results obtained offers the following points of interest: (1) There exists a difference in radio-sensitivity between the two sexes. The females constantly display a greater frequency of both chromosome and chromatid aberrations. They also display a greater frequency of spontaneous aberrations. (2) In both sexes the overall chromosome damage is greater in cells irradiated in stages G2 and G1. These two peaks of greater radiosensitivity are produced by a high frequency of terminal deletions and chromatid exchanges and by a high frequency of dicentrics, respectively. (3) The aberrations are not distributed at random among the various chromosomes. On the average, the Y chromosome is found to be more resistant and the breaks are preferentially localized in the pericentromeric heterochromatin of the X chromosome and of the autosomes. (4) Somatic pairing influences the frequency and type of the chromosome aberrations induced. In this system, such an arrangement of the chromosomes results in a high frequency of exchanges and dicentrics between homologous chromosomes and a low frequency of scorable translocations. Moreover, somatic pairing, probably by preventing the formation of looped regions in the interphase chromosomes, results in the almost total absence of intrachanges at both chromosome and chromatid level.
GENETIC MANIPULATION OF AN ABNORMAL JUMP RESPONSE IN DROSOPHILA
Authors: Kaplan W D , Trout W E 
Published: January 2021

ABSTRACT
The hyperkinetic mutants, Hk1 and Hk2, jump and fall over when an object moves near them. This behavior, the kinetogenic response, has been measured by the experimenter moving his hand above a vial containing a single fly and scoring the number of positive responses in fifty trials. The response is higher in Hk1 than in Hk2 and has remained so over a period of several years and in different genetic backgrounds. The Hk1/Hk2 heterozygote also responds to movements, establishing the allelism of the two mutants.—When Sh5, a shaker mutant at another locus on the X chromosome, is introduced into the same chromosome as Hk1 or Hk2, the response is reduced in proportion to the number of Sh5 mutant genes added.—When Hk1 or Hk2 is heterozygous with a deficiency for the hyperkinetic region of the X chromosome, the expression is more abnormal than the respective Hk1 or Hk2 homozygote. This shows that the mutant genes are producing an altered gene product, or less of the normal, since one mutant gene by itself has a more abnormal expression than two. A tentative explanation has been offered for the observed mutant behaviors.
EFFECTS OF DOSE ON THE INDUCTION OF DOMINANT-LETHAL MUTATIONS AND HERITABLE TRANSLOCATIONS WITH ETHYL METHANESULFONATE IN MALE MICE
Authors: Generoso W M , Russell W L , Huff Sandra W , Stout Sandra K , Gosslee D G 
Published: January 2021

ABSTRACT
Genetic damage by ethyl methanesulfonate (EMS) in male mice was measured at doses ranging from 50 to 300 mg/kg with dominant-lethal mutations and reciprocal translocations as endpoints. No appreciable increase in dominant-lethal mutations was detected following a dose of 100 mg/kg. Dominant lethals induced by EMS were convincingly detected only after a dose of 150 mg/kg, but in the translocation experiment an increase in the genetic effect was detectable at the 50 mg/kg dose. It is likely that dominant lethals had also been induced at the 50 and 100 mg/kg doses, but were not detected due to the relative insensitivity of the dominant%lethal procedure. Thus, for detection of low levels of EMS-induced chromosome breakage, translocations are a much more reliable endpoint than are dominant-lethal mutations. A procedure for large-scale screening of induced translocations is described.—The dominant-lethal dose-response curve, plotted on the basis of living embryos as a percentage of the control value, is clearly not linear as it is markedly concave downward. Similarly, the translocation dose-response curve showed a more rapid increase in the number of translocations with dose than would be expected on the basis of dose-square kinetics. It is clear for both of these endpoints that the effectiveness of EMS in inducing chromosome breakage is proportionately much lower at low doses.
GEOGRAPHICAL PATTERNS OF FOUR POLYMORPHISMS IN ZOARCES VIVIPARUS AS EVIDENCE OF SELECTION
Authors: Christiansen Freddy Bugge , Frydenberg Ove 
Published: January 2021

ABSTRACT
Two unlinked polymorphisms of a marine teleost, one in hemoglobin and one in esterase, show parallel clines through Danish waters, while two unlinked phosphoglucosemutase polymorphisms maintain constant gene frequencies. It is argued that the clinal and the constant polymorphisms cannot be accounted for simultaneously by random genetic drift of selectively neutral genes. It is therefore concluded that selection is responsible for at least one of the two classes of geographical patterns, be it the clinal, the constant, or both.
THE GENETIC STRUCTURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. XII. LINKAGE DISEQUILIBRIUM IN A LARGE LOCAL POPULATION
Authors: Muki Terumi , Watanabe Takao K , Yamaguchi Osamu 
Published: January 2021

ABSTRACT
Seven hundred and three second chromosomes were extracted from a Raleigh, North Carolina population of Drosophila melanogaster in 1970. Additionally, four hundred and eighty-nine third chromosomes were extracted from a large cage population founded from the flies in the 1970 Raleigh collection. The α glycerol-3-phosphate dehydrogenase-1, malate dehydrogenase-1, alcohol dehydrogenase, and α amylase loci were studied from the second chromosomes, and the esterase-6, esterase-C, and octanol dehydrogenase loci were analyzed from the third chromosomes. Inversions, relative viability and fecundity were studied for both classes of chromosomes. The following significant findings were obtained: (1) All loci examined were polymorphic or had at least two alleles at appreciable frequencies. Analysis of the combined data from this experiment with that of Mukai, Mettler and Chigusa (1971) revealed that the frequencies of the genes in the second chromosomes collected in early August were approximately the same over three years. (2) Linkage disequilibria between and among isozyme genes inter se were not detected except in a few cases which can be considered due to non-random sampling. (3) Linkage disequilibria between isozyme genes and polymorphic inversions were detected when the recombination values between the breakage points of the inversions and the genes in question were small. In only a few cases, were second and third order linkage disequilibria including polymorphic inversions detected. (4) Evidence for either variation among genotypes within loci or cumulative effects of heterozygosity was found for viability and fecundity. As a result of these findings, it was tentatively concluded that although selection might be perceptibly operating on some polymorphic isozyme loci, most of the polymorphic isozyme genes are selectively neutral or near-neutral in the populations studied.
THE SURVIVAL OF MUTANTS AT VERY LOW FREQUENCIES IN TRIBOLIUM POPULATIONS
Authors: Sokal Robert R , Kence Aykut , McCauley David E 
Published: January 2021

ABSTRACT
Forty population cages, each with 499 adult T. castaneum of the wild-type UPF strain, received a bb female newly mated with UPF males. Half of the immigrants had a Chicago Black genetic background, the other half a UPF background. These conditions simulate, respectively, the fate of a rare, genetically differing immigrant or the fate of a mutation in populations of considerable size. Adults were censused for 11 discrete generations. The semi-dominant autosomal black gene survived in 26 out of 40 cultures by the end of the experiment, demonstrating its selective advantage at these very low frequencies. The gene increased from an initial frequency of 0.002 to 0.055 (at generation 11) in at least one replicate. Although frequency-dependent fitness has been shown for black at higher frequencies, no such dependence could be demonstrated at the low frequencies of this study. The cultures simulating mutations (immigrants with native backgrounds) had a higher average gene frequency, different distribution of gene frequencies across replicates, and a lower extinction rate of black than did the cultures with alien background immigrants. The observations only partially fitted expectation based on a branching process model. The data show a tendency for the persistence of a few heterozygotes in cultures and for a deficiency of cultures that lost the mutant or those with many heterozygotes. The increase in frequency of black cannot be attributed to increased reproductive success of heterozygotes. The advantage of heterozygotes appears due to delayed developmental period as a result of tactile stimulation and probable differential cannibalism among pupae.
SOME RADIATION EFFECTS ON SEGREGATION IN DROSOPHILA
Authors: Parker D R , Williamson J H 
Published: January 2021

ABSTRACT
Translocation induced in the immature oocyte, in meiotic prophase, affects division I orientation and segregation, the usual result being that the two halves of translocations are directed to opposite poles. Since interchange is usually (if not exclusively) between chromatids, this is to be expected from the creation of illegitimate conjunctions. Good agreement is obtained between patterns of segregations deduced from recovered half-translocation bearing exceptions and the kinds of disomic gametes expected as alternative recoveries from the same division I configurations. Inferences drawn from the study of compound-X females have been found to apply as well in the case of females of normal karyotype. Numerical errors occur predominantly, possibly exclusively, in division I. The rate of induced nondisjunction of specific chromosome pairs varies in relation to the structure of the entire complement, as required if radiation-induced nondisjunction is interchange dependent, but which would be unexpected if the mechanism involved effects on individual spindle fibers, chromosomes, or chromosomal bivalents.
NATURE AND CONSEQUENCES OF INDUCED CHROMOSOME DAMAGE IN MAMMALS
Authors: Searle A G 
Published: January 2021

ABSTRACT
There are marked qualitative and quantitative differences in the patterns of chromosomal damage observed after irradiation of spermatogonia, spermatozoa and oocytes of mice. These differences often result from reduced or zero transmission of particular classes of abberration arising in pre-meiotic germ cells. Probably this is the reason why the level of X-chromosomal and autosomal monosomy is not increased after spermatogonial irradiation. Similarly, the reduced transmission of certain d-se deficiencies may help to explain their low F1 frequency after pre-meiotic as compared with later irradiation. Spermatozoal irradiation has revealed no Robertsonian translocations, but has produced some types of reciprocal translocations which apparently are not transmitted to the F1 after spermatogonial treatment because they prevent maturation of the male pre-meiotic germ cell. Thus they cause sterility in males, but not in females. They include X-autosome and Y-autosome translocations, those giving a metacentric or sub-metacentric chromosome (with reciprocal product present) and those in which one break-point is in or near the centromeric heterochromatin while the other is more distally placed. This last group (which grades into male sub-fertile conditions) gives a preponderance of chain configurations (often with one separate univalent) in heterozygotes of both sexes at meiosis and a high incidence of somatic marker chromosomes. Nondisjunction associated with the univalent generates tertiary trisomics, which are usually male-sterile also and may show phenotypic abnormalities. Sterile males with complete separation of X and Y chromosomes have also been reported after mutagenic treatment of meiotic and post-meiotic germ cells. Such separation seems to prevent a primary spermatocyte from forming a secondary one. The usual derivation (in mouse and man) of tertiary trisomics from mothers rather than from fathers may be due to a similar block, together with a general tendency for male heterozygotes for the parental balanced translocation to be sterile or sub-fertile. Mature oocytes tend to resemble spermatoza in the types of aberration produced by irradiation, which include the male-sterile translocation, but more data are needed. Many of the aberrations described contribute to the human cytogenetic load and can be studied in the mouse from this point of view.
THE USE OF HYBRID SOMATIC CELLS AS AN APPROACH TO MITOCHONDRIAL GENETICS IN ANIMALS
Authors: Dawid Igor B , Horak Ivan , Coon Hayden G 
Published: January 2021

ABSTRACT
We have studied the fate of parental mitochondrial DNA (mtDNA) in hybrid somatic cells derived by Sendai virus-induced fusion of human cells and mouse or rat cells. Many hybrid cell strains were obtained which contained sequences from both human and rodent mtDNA after 40 to 60 population doublings. Some strains were subcloned and cultured further for up to 150 doublings; a large fraction of these strains contained both parental mtDNA sequences at that time.
The relation between human and rodent mtDNA sequences was tested in some of the hybrid cell strains. In a high fraction of strains tested the human and rodent mtDNA sequences were linked to each other by what are most likely covalent bonds. This linkage may be described as "recombination" of mtDNA sequences from two different animals.