bluuebunny/crossref_metadata_2025_split huggingface dataset:
EXTRACHROMOSOMAL ELEMENT DELTA IN DROSOPHILA MELANOGASTER. IX. INDUCTION OF DELTA-RETAINING CHROMOSOME LINES BY MUTATION AND GENE MAPPING
Authors: Minamori Sumio , Sugimoto Kinue 
Published: January 2021

ABSTRACT
[Delta b], symbolized as [δb], is retained by Sb chromosome lines and transmitted through the females to their progeny. Transmission through the males is not directly demonstrable (Minamori 1969a). [delta r], symbolized as [δr], is retained by Sr chromosome lines and transmitted biparentally (Minamori 1971). The multiplication of delta is suppressed at low temperature. All descendant lines derived from Sb-carrying or Sr-carrying flies in which the presence of delta cannot be demonstrated gradually accumulate their specific delta factors over many generations (Minamori 1969b, 1972). The delta factors and the sensitive chromosomes are inseparably associated. This observation led to the assumption that delta may be a copy of a chromosomal gene or a certain agent integrated into the chromosome (Minamori 1972). This assumption was examined in the present study by experiments designed to induce delta-retaining sensitive chromosomes, and to map the gene(s) responsible for delta-retention and/or for sensitivity to the killing action of delta factor. One sensitive chromosome which retained [δb] (Sb chromosome) was obtained in the presence of [δb] out of 2492 insensitive chromosomes which retained no delta; in addition one Sb chromosome was obtained in the presence of [δr] out of 2131 insensitives. The latter finding suggests that Sb might be induced by a mutation caused by [δb] or [δr], but not by integration of either delta into the chromosome. Four Sb chromosomes and one sensitive chromosome which retained [δr] (Sr chromosome) were obtained out of 1970 insensitives when males carrying the chromosome were fed an alkylating mutagen, ethyl methane sulfonate (EMS). The location of delta-retaining genes was examined by crossing-over experiments employing eight Sb and five Sr chromosomes. The genes on these chromosomes were found to be located in the same region or near one another. The gene for [δb], symbolized as Dab, and the gene for [δr], symbolized as Dar, are assumed to be multiple alleles of a locus at 2-24.9. The sensitivity of the chromosomes was modified appreciably by recombination; hence, the genes controlling this trait are assumed to be a polygenic system. The findings obtained in this study lead to the hypothesis that delta may be produced by a chromosomal gene (Da) and transmitted extrachromosomally.
GENETIC POLYMORPHISM AND EVOLUTION IN PARTHENOGENETIC ANIMALS. I. POLYPLOID CURCULIONIDAE
Authors: Suomalainen Esko , Saura Anssi 
Published: January 2021

ABSTRACT
The genetic variability at enzyme loci in different triploid and tetraploid parthenogenetic weevil populations has been elucidated by starch gel electrophoresis. The overall genotype of individual weevils belonging to different populations has been determined for over 25 loci. The results are compared with those obtained for diploid bisexual races of either the same or closely related species. The variation within a parthenogenetic population differs from that in diploid, sexually reproducing populations, i.e. the allele frequencies are not in a Hardy-Weinberg equilibrium. The results indicate that apomictic parthenogenetic populations can differentiate genetically. The genotypes within a population resemble each other more than genotypes belonging to different populations. It is evident that evolution still continues-even if slowed down—in parthenogenetic weevils. A comparison between the allele relationships in geographically isolated polyploid parthenogenetic populations and related diploid bisexual forms does not support the hypothetical hybrid origin of parthenogenesis and polyploidy in weevils. Parthenogenesis within a parthenogenetic weevil species is evidently monophyletic.
ISOLATION OF SUPPRESSIVE SENSITIVE MUTANTS FROM KILLER AND NEUTRAL STRAINS OF SACCHAROMYCES CEREVISIAE
Authors: Somers J M 
Published: January 2021

ABSTRACT
Dominant sensitive mutants were isolated from a killer and a neutral strain of Saccharomyces cerevisiae by treatment with nitrosomethylurethane. Genetic studies suggest that these sensitives arose by mutation of the wild-type cytoplasmic genetic determinants (k) or (n) to a mutant form (s). (s) determinants lack wild-type (k) and (n) activity but are retained in the cell and suppress the replication or activity of the wild-type determinants, converting killer and neutral cells to the sensitive phenotype. These mutants show an obvious similarity in behavior to suppressive petite mutants of yeast.
THE INHERITANCE OF ENZYME VARIANTS FOR TYROSINE AMINOTRANSFERASE, NADP-DEPENDENT MALATE DEHYDROGENASE, NADP-DEPENDENT ISOCITRATE DEHYDROGENASE, AND TETRAZOLIUM OXIDASE IN TETRAHYMENA PYRIFORMIS, SYNGEN 1
Authors: Borden D , Miller E T , Nanney D L , Whitt G S 
Published: January 2021

ABSTRACT
The isozymic patterns of tyrosine aminotransferase, NADP malate dehydrogenase, NADP isocitrate dehydrogenase, and tetrazolium oxidase were examined by starch-gel electrophoresis in Tetrahymena pyriformis, syngen 1. The genetics of the alleles controlling these enzymes was studied through a breeding program. Each enzyme locus was shown to assort vegetatively, as do other loci in this organism. A detailed analysis of the assortment process for the tyrosine aminotransferase locus indicated that the rate of stabilization of heterozygotes into pure types was essentially identical to previously-reported rates for other loci.
SELECTION FOR LINKAGE MODIFICATION II. A RECOMBINATION BALANCE FOR NEUTRAL MODIFIERS
Authors: Feldman Marcus W , Balkau Beverley 
Published: January 2021

ABSTRACT
A stable polymorphic equilibrium may be established at a selectively-neutral gene locus which controls the extent of recombination between two other selected loci. The condition for the existence of the stable polymorphism is analogous to heterozygous advantage. The heterozygote at the modifying locus should produce a recombination fraction allowing the greatest linkage disequilibrium. In the models treated this has the effect of producing the highest mean fitness. The relationship of these findings to general problems of coadaptation is discussed.
THE LAMBDA F MUTANTS BELONG TO TWO CISTRONS
Authors: Boklage Charles E , Wong Emery Chun-Te , Bode Vernon C 
Published: January 2021

ABSTRACT
Amber mutants previously mapped at seven sites in head gene F exhibit two contrasting phenotypes. Mutant F423, located in the right half of gene F, makes defective head particles with normal size λDNA. These particles are complemented by crude lysates of mutants in other head genes. Mutants F785, F471 and F730 map in three adjacent sites in the left half of gene F. They are not complemented by lysates of other head mutants and do not produce headlike particles. Their lysates complement the incomplete heads present in F423. In vivo all three mutants are complemented by F423 but not by each other.
AN EXPERIMENTAL COMPARISON OF INDIVIDUAL, FAMILY AND COMBINATION SELECTION
Authors: Wilson S P 
Published: January 2021

ABSTRACT
Two selection experiments comparing the relative efficiencies of individual, family, and combination selection were conducted. The expected results for larval weight of Tribolium (h 2 = 0.20) and for pupal weight (h 2 = 0.40) were that combination selection would be a more efficient method than family selection, and that family selection would exceed individual selection. In experiment I, individual selection produced more response (P &lt; 0.05) than did combination or family, which was not in agreement with expectation. There was confounding of inbreeding levels and random drift due to differential effective population sizes in the lines selected by different methods. Experiment II consisted of ten single-generation selection tests. An advantage of this approach is that it eleminates the inherent problems of differential inbreeding levels and differential rates of genetic drift due to unequal population sizes among the methods of selection. There were no statistically significant differences in efficiency among the three methods of selection for both traits. This was contrary to theoretical expectations but does suggest that with traits of 20% h2 or higher, and where feasible, one may be justified in basing selection decisions on the phenotype of the individual only. Other advantages of single generation testing are that it allows more precise testing of selection theory and unbiased standard errors for estimates of realized heritability.
COMPLEMENTATION ANALYSIS OF LATE LETHAL MUTANTS OF DROSOPHILA MELANOGASTER
Authors: Shearn Allen 
Published: January 2021

ABSTRACT
Late larval and pupal lethal mutants of Drosophila define those gene functions which are essential for the development of pupae (metamorphosis) but not for embryonic or larval development. In a previous report the isolation of a large number of such mutants was outlined, and a description of the imaginal disc defects in those mutants was described. This report concerns genetic analysis of those mutants. 3746 different pairwise combinations of mutants have been tested for complementation. Only 10 pairs fail to complement. In all of the cases tested, the lethal mutation in each member of a non-complementing pair has a similar map location. In addition to the non-complementing pairs one group of seven partially-complementing mutants has been identified.
Comparisons of the imaginal disc defects within the non-complementing pairs and the lethal hybrids formed by the respective pairs were made to test for uniformity of phenotype. No significant qualitative differences were detected between any non-complementing pairs or their respective hybrids.
RECIPROCAL RECURRENT SELECTION COMPARED TO WITHIN-STRAIN SELECTION FOR INCREASING RATE OF EGG LAY OF TRIBOLIUM UNDER OPTIMAL AND STRESS CONDITIONS
Authors: Orozco Fernando , Bell A E 
Published: January 2021

ABSTRACT
A replicated comparison of reciprocal recurrent selection (rrs) based on crossbred performance and within strain-selection (wss) based on purebred performance was made in three diverse environments over ten generations for the improvement of a heterotic trait, 4-day virgin egg lay of Tribolium castaneum. A selection intensity of 20% based on performance in either an optimum (33°), a mild stress (38°), or a severe stress (28°) environment was applied uniformly. Periodically, the performance of each population was measured in all three environments to provide both direct and correlated responses.—Heritability of egg lay in the base population ranged from 0.36 ± 0.03 in optimum to 0.26 ± 0.03 in severe stress. Estimates of dominance effects assumed significant proportions in severe stress only. Genetic correlations for egg lay in diverse environments were large and positive (.6 to .8) .—Only in severe stress did the rrs response significantly exceed that for wss. Quadratic adjustments fitted t3 response curves revealed that small initial genetic gains under rrs were followed by significantly increasing rates of gain in late generations of selection. The reverse was true for wss. This and evidence from realized heritabilities and genetic correlations suggested that rrs had utilized both additive and dominance effects, but wss response was limited to additive effects.—These results agree with selection theory in demonstrating that purebred selection is mwe efficient than crossbred selection in utilizing additive gene effects. The latter method has merit when non-additive effects assume significant proportions, and this is the more probable case for severe stress conditions.
THE DNA OF CAENORHABDITIS ELEGANS
Authors: Sulston J E , Brenner S 
Published: January 2021

ABSTRACT
Chemical analysis and a study of renaturation kinetics show that the nematode, Caenorhabditis elegans, has a haploid DNA content of 8 x IO7 base pairs (20 times the genome of E. coli). Eighty-three percent of the DNA sequences are unique. The mean base composition is 36% GC; a small component, containing the rRNA cistrons, has a base composition of 51% GC. The haploid genome contains about 300 genes for 4s RNA, 110 for 5s RNA, and 55 for (18 + 28)S RNA.
ENZYME VARIABILITY IN NATURAL POPULATIONS OF DAPHNIA MAGNA II. GENOTYPIC FREQUENCIES IN PERMANENT POPULATIONS
Authors: Hebert Paul D N 
Published: January 2021

ABSTRACT
In permanent habitats populations of the cyclical parthenogen, Daphnia magna, reproduce by continued parthenogenesis and are subject to only sporadic sexual recruitment. The genetic effects of this breeding system have been investigated by analyzing allozyme frequencies in thirteen populations of D. magna—Genotypic frequencies at polymorphic loci characteristically deviated markedly from Hardy-Weinberg proportions and gametic phase imbalance between loci was frequent. Genotypic frequencies were subject to violent, selectively determined oscillations over short periods of time. These observations suggest that permanent populations of D. magna ordinarily consist of a limited number of highly structured genotypes. The adaptational advantages offered by such structuring may have been a major selective factor favoring the evolution of cyclical Parthenogenesis.
REC-MEDIATED RECOMBINATIONAL HOT SPOT ACTIVITY IN BACTERIOPHAGE LAMBDA II. A MUTATION WHICH CAUSES HOT SPOT ACTIVITY
Authors: Lam Stephen T , Stahl Mary M , McMilin Kenneth D , Stahl Franklin W 
Published: January 2021

ABSTRACT
Crosses have been performed which identify phage mutants (chi) which cause recombinational hot spot activity in λ. The hot spot activity is found in crosses of red- gam- chi- strains in rec+ hosts; in the crosses reported here, both the chi- mutations and the hot spot are located near the right end of the chromosome. The hot spot occurs in standard crosses as well as under conditions which block DNA synthesis, and is dependent on a functional host recB gene.—The chi mutation is shown to be dominant, but the tests do not show whether chi is a gene or a site.
ANALYSIS OF GENES CONTROLLING F1 STERILITY IN RICE BY THE USE OF ISOGENIC LINES
Authors: Oka Hiko-Ichi 
Published: January 2021

ABSTRACT
In order to look into the genetic basis of intervarietal F1 sterility in rice (Oryza sativa L.), a series of backcrosses (up to B13) was carried out using Taichung 65 (Japonica type) as the recurrent parent and several Indica varieties as donor parents. A number of "isogenic F1-sterile lines" were isolated by test-crossing fertile F2 plants obtained from the selfing of partly pollensterile backcross segregants. Crossing experiments with the isogenic lines confirmed the author's previous hypothesis that there are sets of duplicate gametic lethals (s genes) and that gametes carrying a double recessive combination (s1s2) of these deteriorate during development, though in the present hypothesis the genes are considered to affect the development of microspores only. Assuming that Taichung 65 has the genotype s1/s1 + 2/+2 and a donor parent (like an isogenic F1-sterile line derived from it) has +1/+1s2/s2, pollen grains with +1s2 have shown a higher fertilizing capacity in the genetic background of Taichung 65 than those with s1 +2, while those with +1 +2 have a lower fertilizing capacity. This certational advantage of alien genes was considered to be an internal mechanism that helped the development of F1 sterility relationships among rice varieties. The isogenic F1-sterile lines derived from different donor parents each had a set of s genes at different loci. Linkage relations were detected between the s loci and three gene markers.
ON THE STRUCTURE OF GENE CONTROL REGIONS
Authors: Wallace Bruce , Kass Thomas L 
Published: January 2021

ABSTRACT
A model emphasizing the possible genetic role of tandem duplications of reverse repeats has been developed as an extension of Crick's (1971) general model for the chromosomes of higher organisms. Although developed initially (1) to explain why random differences in the control regions of individual gene loci might confer a selective advantage on heterozygous individuals as well as (2) to offer the species a means by which such differences might be effected without mutational harm, it seems that control regions built on a foundation of tandemly duplicated reverse repeats would exhibit many properties previously observed in studies on mutable loci in various organisms.
A NOTE ON THE BALANCE BETWEEN RANDOM SAMPLING AND POPULATION SIZE (ON THE 30TH ANNIVERSARY OF G. MALÉCOT'S PAPER)
Authors: Seneta E 
Published: January 2021

ABSTRACT
Wright's model for the effects of random fluctuations in gene frequency in a population of fixed size is generalized to randomly fluctuating population size, and treated from the viewpoint of G. Malécot, using a martingale convergence theorem. The gene frequency approaches a limit, whose value depends on the actual realization, or history, of the process; that is, convergence is with probability one (or: almost surely) in statistical language. The limit does not necessarily represent a state of fixation of either allele; in particular, the limiting probability distribution is not necessarily trivial. For the special case of deterministically varying population size, a necessary and sufficient condition for such non-triviality is given.
ISOLATION AND PROPERTIES OF SELENOMETHIONINE-RESISTANT MUTANTS OF NEUROSPORA CRASSA
Authors: Chen Gregory S , Metzenberg Robert L 
Published: January 2021

ABSTRACT
Mutants resistant to selenomethionine were isolated, and their properties studied. Mapping studies indicate that the mutation sites are located near the eth-1r locus in linkage group I, about ten map units away from the mating type locus. The sites of new mutation are either allelic to or very close to eth-1r. They are resistant not only to selenomethionine but also to ethionine, while the ethionine-resistant mutant, eth-1r, is sensitive to selenomethionine. The selenomethionine-resistant mutants are also temperature-sensitive mutants. However, they can grow at higher temperatures in medium containing 1 M glycerol.—It is very unlikely that the resistance is due to a change in the permeability of the membrane. Aryl sulfatase of se-metr mutants is not repressed by a high concentration of methionine (5 mM), although inorganic sulfate (2 mM) still can cause total repression. The γ-cystathionase levels of the mutants are normal, but the S-adenosylmethionine synthetase levels are only one-tenth of that observed in the wild-type strain. The heat-stability of this enzyme in the mutant is also different from that of the wild-type enzyme suggesting that the mutation might affect the structural gene of S-adenosylmethionine synthetase.
GENETIC ANALYSIS OF MUTATIONS AFFECTING GROWTH OF SACCHAROMYCES CEREVISIAE AT LOW TEMPERATURE
Authors: Singh Arjun , Manney T R 
Published: January 2021

ABSTRACT
A large number of genes control growth of the yeast Saccharomyces cerevisiae at low temperatures (&lt; 10°). Approximately 47 percent of the mutants selected for inability to grow at 4-5°C show increased sensitivity to cycloheximide. In 3 of 4 cases tested, supersensitivity to cycloheximide and inability to grow at the low temperature segregate together and thus appear to be effects of the same mutation. Since many cold-sensitive mutants of bacteria have been found to have altered ribosomes and since cycloheximide resistance in yeast can be caused by ribosomal changes, this suggests that the mutants having low-temperature-sensitive growth may be defective in ribosome-assembly processes at the low temperatures. Two of the lts loci, lts1 and lts3 have been located on chromosome VII and another two, lts4 and lts10 on chromosome IV. A mutation, cyh10, conferring cycloheximide resistance, but not cold sensitivity, has been located close to the centromere on chromosome II.
GENE DIFFERENCES BETWEEN THE SEX RATIO AND STANDARD GENE ARRANGEMENTS OF THE X CHROMOSOME AND LINKAGE DISEQUILIBRIUM BETWEEN LOCI IN THE STANDARD GENE ARRANGEMENT OF THE X CHROMOSOME IN DROSOPHILA PSEUDOOBSCURA
Authors: Prakash Satya 
Published: January 2021

ABSTRACT
The Standard and Sex Ratio gene arrangements of the X chromosome of D. pseudobscura differ from each other in allele frequencies at the four X chromosome loci, esterase-5, adult acid phosphatase-6, phosphoglucomutase-1 and octanol dehydrogenase-3. The Standard arrangement which is the common arrangement in all populations is polymorphic at these loci in varying degrees, the geographically less widespread Sex Ratio arrangement has little polymorphism and is genically predominantly E-51.04 AP-6- Pgm11.0 ODH-31.0. The Sex Ratio arrangement from different populations is alike at all of the four loci, the Standard arrangement shows some gene frequency differences among populations. The Standard and Sex Ratio arrangements differ from each other by three inversions which suggests that the two arrangements are "old". Gene differences between these two chromosome arrangements can be explained due to differential natural selection of alleles in the Standard and Sex Ratio arrangments.—The order and percent recombination among these four loci in the Standard arrangement are: E-5—.294—AP-6—.335—Pgm-1—.024—ODH-3. The Standard X chromosomes from four different wild populations were analyzed for evidence of linkage disequilibrium between pairs of loci at these four loci. No evidence of linkage disequilibrium between pairs of loci was obtained. However, when linkages involving simultaneously three loci, E-5, AP-6 and Pgm-1 are considered, then significant departure from linkage equilibrium is observed.
SEGREGATION AND RECOMBINATION OF NON-MENDELIAN GENES IN CHLAMYDOMONAS
Authors: Gillham Nicholas W , Boynton John E , Lee Robert W 
Published: January 2021

ABSTRACT
Non-Mendelian genes in Chamydomonas reinhardtii are inherited in a uniparental (UP) fashion. Most zygotes and their progeny receive UP genes only from the mt + or maternal parent. However, a few exceptional zygotes are also found in which the mt - or paternal UP genome is transmitted. Most of the exceptional zygotes are biparental in that their progeny segregate UP genes transmitted by both parents. As a result, biparental zygotes have been extensively used to study the rules governing UP inheritance.
The frequency of biparental zygotes can be greatly increased if the maternal parent is irradiated with ultraviolet light prior to mating. Based principally on studies with ultraviolet-induced biparental zygotes, Sager has argued that a vegetative cell contains two copies of the UP genome and that the progeny of a biparental zygote receive a copy derived from each parent. Results reported in this paper with spontaneous and ultraviolet-induced biparental zygotes do not support the two copy model, but argue for a mulitple copy model with most of the copies normally being transmitted by the maternal parent. A multiple copy model which accounts for both Sager's results and ours is presented.