bluuebunny/crossref_metadata_2025_split huggingface dataset:
DISTRIBUTION AND FREQUENCY OF TANDEM DUPLICATIONS OF THE rII REGION OF BACTERIOPHAGE T4D
Authors: Parma David H , Heath G Thomas , Che Chia-Chung , Annest J L 
Published: April 2021

ABSTRACT
Genetic analyses of 49 duplications of the rII region of bacteriophage T4D suggests that there is a non-random relationship between the end points of duplicated segments, that relaxed packaging restrictions have little if any effect on the distribution of duplications, that segregation is 3-4 times more frequent than normal recombination for the same interval, and that non-tandem duplications are rare. Extrapolation of the r1231x rJ101 cross data suggests that the minimum frequency of duplications/genome is 1.7 x 10-6, but possibly 3.4 x 10-4.
CONTEXT EFFECTS ON NONSENSE CODON SUPPRESSION IN ESCHERICHIA COLI
Authors: Feinstein Sheldon I , Altman Sidney 
Published: April 2021

ABSTRACT
The influence of mRNA context on nonsense codon suppression has been studied by suppression measurements at one site in the Escherichia coli trpE gene and at two sites in the trpA gene. The ratio of suppression efficiencies of amber and ochre codons at each site (homotopic pairs) has been compared using ochre suppressing derivatives of tRNA1 Tyr. This ratio is independent of differential effects of the inserted amino acid on enzyme function. We have found that mRNA context can change the ratio of suppression efficiencies of homotopic nonsense codons at the three sites in the trp gene system over a ten-fold range. The causes of such variation, and, in particular the effect of certain adjacent nucleotides on nonsense codon suppression are considered.
FINE-STRUCTURE ANALYSIS AND GENETIC ORGANIZATION AT THE BASE OF THE X CHROMOSOME IN DROSOPHILA MELANOGASTER
Authors: Lifschytz Eliezer 
Published: April 2021

ABSTRACT
Genetic organization at the base of the X chromosome was studied through the analysis of X-ray-induced deficiencies. Deficiencies were recovered so as to have a preselected right end "anchored" in the centric heterochromatin to the right of the su(f) locus. "Free" ends of deficiencies occurred at any of 22 intervals in Section 20 and in the proximal portion of Section 19 of Bridges' (1938) polytene chromosome map. The distribution of 130 such free ends of deficiencies induced in normal, In(1)sc 8, and In(1)wm4 chromosomes suggests that on the single section level, genes are flanked by "hot" or "cold" sites for X-ray-induced breaks, and that occurrence of the hot spots is dependent on their interaction with the fixed-end sites in the centric heterochromatin. In the light of these results, it is argued that long heterochromatic sequences separate the relatively few genes in Section 20, and thus endow it with several characteristics typical of heterochromatic regions. Section 20 is considered to be a transition region between the mostly heterochromatic and mostly euchromatic regions of the X chromosome; the differences between them are suggested as being merely quantitative.
THEORETICAL POPULATION GENETICS OF REPEATED GENES FORMING A MULTIGENE FAMILY
Authors: Ohta Tomoko 
Published: April 2021

ABSTRACT
The evolution of repeated genes forming a multigene family in a finite population is studied with special reference to the probability of gene identity, i.e., the identity probability of two gene units chosen from the gene family. This quantity is called clonality and is defined as the sum of squares of the frequencies of gene lineages in the family. The multigene family is undergoing continuous unequal somatic crossing over, ordinary interchromosomal crossing over, mutation and random frequency drift. Two measures of clonality are used: clonality within one chromosome and that between two different chromosomes. The equilibrium properties of the means, the variances and the covariance of the two measures of clonality are investigated by using the diffusion equation method under the assumption of constant number of gene units in the multigene family. Some models of natural selection based on clonality are considered. The possible significance of the variance and covariance of clonality among the chromosomes on the adaptive differentiation of gene families such as those producing antibodies is discussed.
A SEX-LINKED GENE CONTROLLING THE ONSET OF SEXUAL MATURITY IN FEMALE AND MALE PLATYFISH (XIPHOPHORUS MACULATUS), FECUNDITY IN FEMALES AND ADULT SIZE IN MALES
Authors: Kallman Klaus D , Borkoski Valerie 
Published: April 2021

ABSTRACT
A sex-linked gene, P, controls the onset of sexual maturity in the platyfish, Xiphophorus maculatus. The activity of this gene is correlated with the age and size at which the gonadotropic zone of the adenohypophysis differentiates and becomes physiologically active. Immature fish of all genotypes grow at the same rate; however, as adults, males with "early" genotypes are significantly smaller than males of "late" genotypes, since growth rate declines strongly under the influence of androgenic hormone. Five alleles, P1… P5, have been identified from natural populations that under controlled conditions cause gonad maturation between eight and 73 weeks. P1P1 males become mature at eight weeks and 21 mm, P2P2 and P3P3 males between eleven and 13.5 weeks and 25 to 29 mm, and P4P4 males at 25 weeks and 37 mm. Since P5 is X-linked, no males homozygous for P5 could be produced. The difference between P2 and P3 is largely based upon their interaction with P5. P3P5 males mature at 17.5 weeks and 33.5 mm and P2P5 males at 28 weeks and 38 mm. The rate of transformation of the unmodified anal fin into a gonopodium, which is under androgenic control, is directly related to the age at initiation of sexual maturity, ranging from 3.2 weeks in P1P1 males to seven weeks in P2P5 males. These differences may reflect different levels of circulating gonadotropic and androgenic hormones.—In two genotypes of females, initiation of vitellogenesis was closely correlated with size and this critical size was independent of age (e.g., 21 mm for P1P1). In a third genotype (P1P5) the minimum size for vitellogenesis decreased with increasing age, so that females would mature as early as eleven weeks, provided they had attained at least 29 mm, but at 25 weeks even females as small as 23 mm possessed ripe gonads. For P5P5 females, which become mature between 34 and 73 weeks of age, there is no correlation between size and initiation of vitellogenesis. In all four genotypes of females examined, egg number is strongly correlated with size, but the regression of egg number on standard length is distinct for each genotype. Late maturation of P5P5 females is not offset by an increased number of eggs; for this genotype there is a strong negative correlation between age and number of eggs. Heterozygous fish always mature later than those homozygous for the "earlier" allele. The site of action of the P locus could be the pituitary gland, the hypothalamus or higher centers of the brain where peripheral information is transduced into an appropriate signal required for the activation of the hypothalamus-pituitary-gonadal axis. The P gene could also control the peripheral information. The platyfish may be a useful model to test theories concerning the evolution of life history strategies.
ERYTHROMYCIN RESISTANCE AND THE CHLOROPLAST RIBOSOME IN CHLAMYDOMONAS REINHARDI
Authors: Davidson Jeffrey N , Hanson Maureen R , Bogorad Lawrence 
Published: April 2021

ABSTRACT
Five classes of erythromycin-resistant mutants of Chlamydomonas reinhardi have been identified. Each class corresponds to a different genetic locus, three nuclear and two chloroplast. The three nuclear loci appear to be unlinked, while Conde et al. (1975) have shown that the two chloroplast loci are linked, but not allelic. Mutants in each class have a unique pattern of cross-resistance in vivo to other antibiotics (lincomycin, carbomycin, and cleocin) that affect chloroplast protein synthesis. The chloroplast ribosomes from each class have a distinctive erythromycin-binding reaction in vitro.—Haploid and diploid strains containing combinations of different genes affecting the chloroplast ribosome were constructed to probe ribosome structure. New phenotypes were obtained by such combinations, demonstrating interactions between the gene products of a number of loci specifying ribosome components.
PARTIAL DOMINANCE OF EMS-INDUCED MUTATIONS AFFECTING VIABILITY IN DROSOPHILA MELANOGASTER
Authors: Temin Rayla Greenberg 
Published: April 2021

ABSTRACT
More than 700 EMS-treated second chromosomes marked with either cn (cinnabar) or bw (brown), and derived from long-inbred stocks, were measured for their heterozygous effects on viability in both isogenic (homozygous) and nonisogenic (heterozygous) backgrounds. Each test was replicated five times. When the background was homozygous, flies heterozygous for a treated chromosome were an average of 2.1% less viable, per 0.005 m EMS, than flies heterozygous for an untreated chromosome. Classified according to their homogous effect in an accompanying series of crosses, the lethal-bearing chromosomes (L), which carry genes of less drastic effects as well, reduced the viability of their heterozygous carriers by 3.3%, severe detrimentals (Ds) by 2.2%, and mild detrimentals (Dm) by 1.2% at this dose. In the heterozygous background, the mean heterozygous disadvantage for the entire group was 1%, or about half as large.——When computed separately for each count from a single mating, the heterozygous disadvantage was consistently greatest for the earliest counts (4.8%), next highest for the middle count (0.8%), and lowest in the latest count (0.5%), in the homozygous background, indicating that mutant heterozygotes were delayed in time of emergence. The figures in the heterozygous background were, again, reduced, but in the same direction.—The relative viability disadvantage of the cn marker was about 2½ times greater in the homozygous than in the heterozygous background, further supporting the conclusion that the homozygous background can accentuate differences. The enhancement of treatment and marker effects could be a direct result of the level of background heterozygosity per se or attributable to the reduced vigor of the inbred strain.—Dominance, a measure of the heterozygous effect of a mutant relative to its homozygous effect, is greater for genes with small homozygous disadvantage than for more drastic genes. In the homozygous background the average dominance for lethals was 0.019 in contrast to 0.183 for mild detrimentals, supporting other published results suggesting that genes with milder effect, because they occur more frequently, have a greater impact on a population.—The homozygous D:L ratio of EMS mutations was 0.266 and the Dm: L ratio, 0.092, which are lower than comparable load ratios for spontaneous mutations, but greater than for X-ray induced mutations.
MULTIPLE ALLELE APPROACH TO THE STUDY OF GENES IN DROSOPHILA MELANOGASTER THAT ARE INVOLVED IN IMAGINAL DISC DEVELOPMENT
Authors: Shearn Allen , Hersperger Grafton , Hersperger Evelyn , Pentz Ellen Steward , Denker Paul 
Published: April 2021

ABSTRACT
The phenotypes of five different lethal mutants of Drosophila melanogaster that have small imaginal discs were analyzed in detail. From these results, we inferred whether or not the observed imaginal disc phenotype resulted exclusively from a primary imaginal disc defect in each mutant. To examine the validity of these inferences, we employed a multiple-allele method. Lethal alleles of the five third-chromosome mutations were identified by screening EMS-treated chromosomes for those which fail to complement with a chromosome containing all five reference mutations. Twenty-four mutants were isolated from 13,197 treated chromosomes. Each of the 24 was then tested for complementation with each of the five reference mutants. There was no significant difference in the mutation frequencies at these five loci. The stage of lethality and the imaginal disc morphology of each mutant allele were compared to those of its reference allele in order to examine the range of defects to be found among lethal alleles of each locus. In addition, hybrids of the alleles were examined for intracistronic complementation. For two of the five loci, we detected no significant phenotypic variation among lethal alleles. We infer that each of the mutant alleles at these two loci cause expression of the null activity phenotype. However, for the three other loci, we did detect significant phenotypic variation among lethal alleles. In fact, one of the mutant alleles at each of these three loci causes no detectable imaginal disc defect. This demonstrates that attempting to assess the developmental role of a gene by studying a single mutant allele may lead to erroneous conclusions. As a byproduct of the mutagenesis procedure, we have isolated two dominant, cold-sensitive mutants.
ABSENCE OF INTERFERENCE IN ASSOCIATION WITH GENE CONVERSION IN SORDARIA FIMICOLA, AND PRESENCE OF INTERFERENCE IN ASSOCIATION WITH ORDINARY RECOMBINATION
Authors: Kitani Y 
Published: April 2021

ABSTRACT
From the analysis of large samples of gene conversion asci in the g locus of Sordaria fimicola, it was found that neither the conversion event itself nor conversion-associated recombination of flanking markers cause either chiasma or chromatid interference with crossing over in a neighboring interval. The presence of more than one kind of crossover event, one causing interference the other not, is considered. The existence of two kinds of gene loci, one of single-cistron composition and the other of multiple-cistron composition, is discussed in relation to reciprocal recombination within a locus.
DELETIONS OF THE ISO-1-CYTOCHROME c AND ADJACENT GENES OF YEAST: DISCOVERY OF THE OSM1 GENE CONTROLLING OSMOTIC SENSITIVITY
Authors: Singh Arjun , Sherman Fred 
Published: April 2021

ABSTRACT
Some of the deletions in the yeast Saccharomyces cerevisiae that encompass the CYC1 gene, which determines iso-1-cytochrome c, extend into the OSM1 gene, causing inhibition of growth on hypertonic media, and into the RAD7 gene, causing sensitivity to UV light. Two deletions (cyc1-363 and cyc1-367) encompass only the CYC1 gene, two deletions (cyc1-366 and cyc1-368) encompass the CYC1 and OSM1 genes, three deletions (cyc1-1, cyc1-364 and cyc1-365) encompass the CYC1, OSM1 and RAD7 genes, while none of the deletions extend into the closely linked SUP4 gene.
INTERNUCLEAR GENETIC TRANSFER IN DIKARYONS OF SCHIZOPHYLLUM COMMUNE. II. DIRECT RECOVERY AND ANALYSIS OF RECOMBINANT NUCLEI
Authors: Leonard Thomas J , Gaber Richard F , Dick Stanley 
Published: April 2021

ABSTRACT
The recessive gene, mound (mnd), allows the appearance of globose masses of compacted hyphae. Dikaryons of Schizophyllum commune that are heteroallelic for mnd [(mosaic dikaryons: (mnd+ mnd +)] have been successfully dedikaryotized in cholate-containing medium in order to recover the component nuclear types directly. The relative proportion of the two recovered monokaryotic types shows in all cases a marked deviation from 1:1. Hyphae from nonmound mycelial regions yield monokaryotic types identical to those originally used to form the dikaryons. In hyphae from mound-forming regions, however, homoallelism of the mnd allele has been demonstrated; the nuclear type that formerly contained the mnd + allele acquired a mnd allele.—The process of internuclear transfer or recombination is unaccompanied by the simultaneous alteration of any additional genetic markers carried by the recipient nucleus. The newly acquired mnd allele segregates in Mendelian fashion in subsequent outcrosses and appears to be chromosomally located. A novel process of somatic recombination, with several features distinct from classical parasexual mitotic recombination, appears to be in operation.
STUDIES OF LINKAGE IN POPULATIONS. IX. THE EFFECT OF ALTITUDE ON X-CHROMOSOMAL ARRANGEMENT COMBINATIONS IN DROSOPHILA ROBUSTA
Authors: Levitan Max 
Published: April 2021

ABSTRACT
Data are presented concerning the gene arrangements in both arms of the X-chromosome of Drosophila robusta in eight altitudinal transects. The major change appears to be the increase of gene arrangement XL-1 (and decrease in XL, sometimes also XL-2) with increasing altitude. In each transect only one combination of XL-1 with a right arm arrangement seems primarily responsible for the increases with altitudinal change, and only one combination of XL for the decreases. In four of the transects the increasing combination appears to be XL-1.XR, XL-1.XR-2 in the other four. A substantial decrease with elevation in XL-2.XR-2 occurs only in the four areas where XL-1.XR exhibits the major increase. These results indicate that interactions between arrangements play a significant role in the adaptation of this species to altitude. The interactions appear related to the X-chromosomal linkage equilibriums in these regions. The data also suggest that the species employs its inversions in different methods of adaptation in the Appalachian Mountains from those it uses in other parts of the range.
MAINTENANCE OF GENETIC VARIABILITY UNDER THE JOINT EFFECT OF MUTATION, SELECTION AND RANDOM DRIFT
Authors: Li Wen-Hsiung 
Published: April 2021

ABSTRACT
Formulae are developed for the distribution of allele frequencies (the frequency spectrum), the mean number of alleles in a sample, and the mean and variance of heterozygosity under mutation pressure and under either genic or recessive selection. Numerical computations are carried out by using these formulae and Watterson's (1977) formula for the distribution of allele frequencies under overdominant selection. The following properties are observed: (1) The effect of selection on the distribution of allele frequencies is slight when 4Ns ≤ 4, but becomes strong when 4Ns becomes larger than 10, where N denotes the effective size and s the selective difference between alleles. Genic selection and recessive selection tend to force the distribution to be U-shaped, whereas overdominant selection has the opposite tendency. (2) The mean total number of alleles in a sample is much more strongly affected by selection than the mean number of rare alleles in a sample. (3) Even slight heterozygote advantage, as small as 10-5, increases considerably the mean heterozygosity of a population, as compared to the case of neutral mutations. On the other hand, even slight genic or recessive selection causes a great reduction in heterozygosity when population size is large. (4) As a test statistic, the variance of heterozygosity can be used to detect the presence of selection, though it is not efficient when the selection intensity is very weak, say when 4Ns is around 4 or less. A model, which is somewhat similar to Ohta's (1976) model of slightly deleterious mutations, has been proposed to explain the following general patterns of genic variation: (i) There seems to be an upper limit for the observed average heterozygosities. (ii) The distribution of allele frequencies is U-shaped for every species surveyed. (iii) Most of the species surveyed tend to have an excess of rare alleles as compared with that expected under the neutral mutation hypothesis.
ORGANIZATION OF THE ROSY LOCUS IN DROSOPHILA MELANOGASTER: FURTHER EVIDENCE IN SUPPORT OF A CIS-ACTING CONTROL ELEMENT ADJACENT TO THE XANTHINE DEHYDROGENASE STRUCTURAL ELEMENT
Authors: McCarron M , O'Donnell J , Chovnick A , Bhullar B S , Hewitt J , Candido E P M 
Published: April 2021

ABSTRACT
The present report summarizes our recent progress in the genetic dissection of an elementary genetic unit in a higher organism, the rosy locus (ry: 3-52.0) in Drosophila melanogaster. Pursuing the hypothesis that the rosy locus includes a noncoding control region, as well as a structural element coding for the xanthine dehydrogenase (XDH) peptide, experiments are described that characterize and map a rosy locus variant associated with much lower than normal levels of XDH activity. Experiments are described that fail to relate this phenotype to alteration in the structure of the XDH peptide, but clearly associate this character with variation in number of molecules of XDH per fly. Large-scale fine-structure recombination experiments locate the genetic basis for this variation in the number of molecules of XDH per fly to a site immediately to the left of the XDH structural element within a region previously designated as the XDH control element. Moreover, experiments clearly separate this "underproducer" variant site from a previously described "overproducer" site within the control region. Examination of enzyme activity in electrophoretic gels of appropriate heterozygous genotypes demonstrates the cis-acting nature of this variation in the number of molecules of XDH. A revision of the map of the rosy locus, structural and control elements is presented in light of the additional mapping data now available.
HETEROCHROMATIC EFFECTS ON THE BEHAVIOR OF REVERSED ACROCENTRIC COMPOUND-X CHROMOSOMES IN DROSOPHILA MELANOGASTER
Authors: Sandler L , O'Tousa Joseph 
Published: April 2021

ABSTRACT
Previous studies of reversed acrocentric compound-X chromosomes suggested peculiar influences of heterochromatin on both the synthesis and meiotic behavior of such compounds. It seemed, with respect to synthesis, that the long arm of the Y chromosome on an X.YL chromosome was necessary in order for the heterochromatic exchange giving rise to reversed acrocentrics to occur, even though YL itself did not participate in the compound-generating event. With respect to behavior, the resulting compounds appeared, presumably as a consequence of their singular generation, to contain an interstitial heterochromatic region that caused the distribution of exchanges between the elements of the compound to be abnormal (many zero and two-exchange tetrads with few, if any, single-exchange tetrads). Removing the interstitial heterochromatin (or, curiously, appending YL as a second arm of the compound) eliminated the recombinational anomalies and resulted in typical tetrad distributions.—We provide evidence that these peculiarities, while presumably real, were likely the consequence of a special X.YL chromosome that was used to synthesize the reversed acrocentrics examined in the early studies and are not general properties of either reversed acrocentric compounds or of interstitial heterochromatin. However, we show that specific heterochromatic regions do, in fact, profoundly influence the behavior of (apparently all) reversed acrocentric compound-X chromosomes. In particular, we demonstrate that specific portions of the Y chromosome and of the basal X-chromosome heterochromatin, when present as homologs for reversed acrocentric compounds, markedly and coordinately increase bath the frequency of exchange between the elements of the compound and the fertility (egg production) of compound-bearing females. It is, we suppose, some aspect of this heterochromatic effect, produced by the% special X.YL chromosome, that caused the earlier-analyzed compounds to exhibit the observed anomalies.
SELECTION ON RECOMBINATION IN CLINES
Authors: Charlesworth D , Charlesworth B 
Published: April 2021

ABSTRACT
Computer runs have been done to examine SLATKIN'S (1975) model for selection on recombination rates in linear sets of populations with environmental changes affecting two loci. In order to determine whether the suggested selection pressures on recombination do, in fact, exist, we follow the changes in frequency at a third locus that is polymorphic for alleles affecting the recombination rate between the two selected loci. With haploid or diploid selection models, there can be selection for increased recombination if the parameter values are chosen suitably, but changes in parameter values often lead to changes in the direction of selection, so that decreased recombination is favored, The selection for increased recombination is usually weak, while that for decreased recombination is frequently much stronger. Weaker selection on the selected loci often leads to increasing selection for decreased recombination.