bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE TRANSPOSABLE ELEMENT Ds AFFECTS THE PATTERN OF INTRAGENIC RECOMBINATION AT THE bz AND R LOCI IN MAIZE
Authors: Dooner H K , Kermicle J L 
Published: January 2021

ABSTRACT
Insertion of the transposable element Ds into either the bz or R locus affects intragenic recombination in various ways. We have examined here one aspect of this problem; namely, the distribution of flanking markers among intragenic recombinations produced by different types of heterozygotes carrying Ds insertion mutations. Heteroallelic combinations of a Ds insertion mutation and a mutation borne on a structurally normal chromosome generate a majority of intragenic recombinants of a crossover type. In contrast to this, most intragenic recombinants obtained from heterozygotes between two different Ds insertion mutations have a parental arrangement of outside markers. Therefore, the resolution of the recombination intermediate would appear to depend on the nature of the mutations in the heterozygote.
SUPPRESSORS OF THE ras2 MUTATION OF SACCHAROMYCES CEREVISIAE
Authors: Cannon John F , Gibbs Jackson B , Tatchell Kelly 
Published: January 2021

ABSTRACT
Saccharomyces cerevisiae contains two members of the ras gene family. Strains with disruptions of the RAS2 gene fail to grow efficiently on nonfermentable carbon sources. This growth defect can be suppressed by extragenic mutations called sra. We have isolated 79 independent suppressor mutations, 68 of which have been assigned to one of five loci. Eleven additional dominant mutations have not been assigned to a specific locus. Some sra1 and SRA4 and all SRA3 mutations were RAS independent, allowing growth of yeast cells that lack a functional RAS gene. Mutations in sra1, SRA3, SRA4 and sra6 are linked to his6, ino1, met3 and ade6, respectively. Some sra mutants have pleitropic phenotypes that affect glycogen accumulation, sporulation, viability, respiratory capacity and suppression of two cell-division-cycle mutations, cdc25 and cdc35. The proposed functions of many of the suppressor genes are consistent with the model in which RAS activates adenylate cyclase.
THE UNDERLYING BASES OF GENE EXPRESSION DIFFERENCES IN STABLE TRANSFORMANTS OF THE ROSY LOCUS IN DROSOPHILA MELANOGASTER
Authors: Daniels Stephen B , McCarron Margaret , Love Carol , Clark Stephen H , Chovnick Arthur 
Published: January 2021

ABSTRACT
This report represents a continuation of our laboratory's effort to understand the major phenomena associated with P-M dysgenesis-mediated transformation in Drosophila. A group of stable transformants are characterized with respect to rosy gene expression. Stable, true-breeding, line-specific variants in gene expression are described. These are shown to be associated with single transposons present in each line, and the lines are free of functional P elements. The effects on expression are cis-acting, and there are no identifiable rosy DNA sequence lesions associated with these transposons. Evidence is presented that demonstrates that two features of the transformation experimental system are responsible for such variation. The first relates to the fact that the transposons insert at numerous genomic sites. Both heterochromatic and euchromatic position effects are characterized. The second relates to the fact that transformation involves dysgenic mobilization of a P-element transposon. This process is mutagenic, and such a mutation is characterized.
AUTOSOMAL MODIFIERS OF THE BOBBED PHENOTYPE ARE A MAJOR COMPONENT OF THE rDNA MAGNIFICATION PARADOX IN DROSOPHILA MELANOGASTER
Authors: Marcus Craig H , Zitron Anne E , Wright David A , Hawley R Scott 
Published: January 2021

ABSTRACT
rDNA magnification in Drosophila melanogaster is defined experimentally as the ability of bb/Ybb - males to produce exceptional progeny that are wild type with respect to rDNA associated phenotypes. Here, we show that some of these bobbed-plus progeny result not from genetic reversion at the bb locus but rather from variants at two or more autosomal loci that ameliorate the bobbed phenotype of rDNA deficient males in Drosophila. In doing so we resolve several aspects of a long-standing paradox concerning the phenomenon of rDNA magnification. This problem arose from the use of two genetic assays, which were presumed to be identical, but paradoxically, produced conflicting data on both the kinetics of reversion and the stability of magnified bb + chromosomes. We resolve this problem by demonstrating that in one assay bobbed-plus progeny arise primarily by genetic reversion at the bobbed locus, whereas in the other assay bobbed-plus progeny arise both by reversion and by an epistatic effect of autosomal modifiers on the bobbed phenotype. We further show that such modifiers can facilitate the appearance of phenotypically bobbed-plus progeny even under conditions where genetic reversion is blocked by magnification defective mutants. Finally, we present a speculative model relating the action of these modifiers to the large increases in rDNA content observed in males undergoing magnification.
PRECOCIOUS MEIOTIC CENTROMERE SEPARATION OF A NOVEL YEAST CHROMOSOME
Authors: O'Rear Jules , Rine Jasper 
Published: January 2021

ABSTRACT
In Saccharomyces cerevisiae, a reciprocal translocation between chromosome II and a linear plasmid carrying a centromere (CEN6) has split chromosome II into two fragments: one, approximately 530 kilobase pairs (kbp) in size, has the left arm and part of the right arm of chromosome II; the other, a telocentric fragment approximately 350 kbp in size, has CEN6 and the rest of the right arm of chromosome II. A cross of this yeast strain with a strain containing a complete chromosome II exhibits a high frequency of precocious centromere separation (separation of sister chromatids during meiosis I) of the telocentric fragment. Precocious centromere separation is not due to the position of the centromere per se, since diploids that are homozygous for both fragments of chromosome II segregate the telocentric fragment with normal meiotic behavior. The precocious centromere separation described here differs from previously described examples in that pairing and synapsis of this telocentric chromosome seem to be normal. One model of how centromeres function in meiosis is that replication of the centromere is delayed until the second meiotic division. Data presented in this paper indicate that replication of the centromere is complete before the first meiotic division. The precocious separation of the centromere described here may be due to improper synapsis of sequences flanking the centromere.
GENETIC STUDIES OF UNUSUAL LOCI THAT AFFECT BODY SHAPE OF THE NEMATODE CAENORHABDITIS ELEGANS AND MAY CODE FOR CUTICLE STRUCTURAL PROTEINS
Authors: Kusch Meredith , Edgar R S 
Published: January 2021

ABSTRACT
In Caenorhabditis elegans, four loci (sqt-1, sqt-2, sqt-3 and rol-8) in which mutations affect body shape and cuticle morphology have unusual genetic properties. (1) Mutant alleles of sqt-1 can interact to produce animals with a variety of mutant phenotypes: left roller, right roller, dumpy and long. At least three mutant phenotypes are specified by mutations in the sqt-3 locus. (2) Most alleles at these loci are either dominant or cryptic dominant (i.e., are dominant only in certain genetic backgrounds). (3) Most alleles of these loci exhibit codominance. (4) Two putative null alleles of the sqt-1 locus produce a wild-type phenotype. (5) Many alleles of these genes demonstrate unusual intergenic interactions that are not the result of simple epistasis: animals doubly heterozygous for mutations at two loci often display unexpected and unpredictable phenotypes. We suggest that these genetic properties might be expected of genes, such as the collagen genes, the products of which interact to form the animal's cuticle, and which are member genes of a gene family.
MUTATIONS WITH DOMINANT EFFECTS ON THE BEHAVIOR AND MORPHOLOGY OF THE NEMATODE CAENORHABDITIS ELEGANS
Authors: Park Eun-Chung , Horvitz H Robert 
Published: January 2021

ABSTRACT
We have analyzed 31 mutations that have dominant effects on the behavior or morphology of the nematode Caenorhabditis elegans. These mutations appear to define 15 genes. We have studied ten of these genes in some detail and have been led to two notable conclusions. First, loss of gene function for four of these ten genes results in a wild-type phenotype; if these genes represent a random sample from the genome, then we would estimate that null mutations in about half of the genes in C. elegans would result in a nonmutant phenotype. Second, the dominant effects of mutations in nine of these ten genes are caused by novel gene functions, and in all nine cases the novel function is antagonized by the wild-type function.
GENETIC CONTROLS OVER ACTIVITIES OF TYROSINASE AND DOPACHROME CONVERSION FACTOR IN MURINE MELANOCYTES
Authors: Lamoreux M Lynn , Woolley Catherine , Pendergast Phil 
Published: January 2021

ABSTRACT
We evaluated the three catalytic activities of tyrosinase and one activity of dopachrome conversion factor (DCF) in extracts made from skins of 6-day-old yellow and nonyellow mice. At least one of the catalytic activities of tyrosinase and of DCF correlate with the color of pigment being produced in the hair follicles of the mice. We use these data to evaluate existing hypotheses about the mechanism of the interacting genetic controls over melanogenesis.
GENETIC DIVERGENCE UNDER UNIFORM SELECTION. II. DIFFERENT RESPONSES TO SELECTION FOR KNOCKDOWN RESISTANCE TO ETHANOL AMONG DROSOPHILA MELANOGASTER POPULATIONS AND THEIR REPLICATE LINES
Authors: Cohan Frederick M , Hoffmann Ary A 
Published: January 2021

ABSTRACT
We have tested the hypothesis that genetic differences among conspecific populations may result in diverse responses to selection, using natural populations of Drosophila melanogaster. Selection for ethanol tolerance in a tube measuring knockdown resistance was imposed on five West Coast populations. In 24 generations the selected lines increased their mean knockdown times, on average, by a factor of 2.7. An initially weak latitudinal cline was steepened by selection. The two southernmost populations showed the same increases in the selected character, but differed consistently in their correlated responses in characters related to ethanol tolerance. This result indicates that the populations responded to selection by different genetic changes. Selection decreased female body weight and increased resistance to acetone, suggesting components of the response unrelated to ethanol metabolism. The Adhs allele was favored by selection in all populations at the onset, but increased in frequency only in the selected lines of the southernmost population. There was a correlation between latitude and Adh frequency changes, suggesting that fitnesses of the Adh alleles were dependent on the genetic background. Genetic background also had a large effect on the loss of fitness due to selection. Genetic drift between replicate lines caused more variation in selection response than initial genetic differences between populations. This result demonstrates the importance of genetic drift in divergence among natural populations undergoing uniform selection, since the effective population sizes approached those of small natural populations. Drift caused greater divergence between selected replicates than control replicates. Implications of this result for the genetic model of selection response are discussed.
ACTIVITY OF THE SEX-DETERMINING GENE tra-2 IS MODULATED TO ALLOW SPERMATOGENESIS IN THE C. ELEGANS HERMAPHRODITE
Authors: Doniach Tabitha 
Published: January 2021

ABSTRACT
In the nematode C. elegans, there are two sexes, the self-fertilizing hermaphrodite (XX) and the male (XO). The hermaphrodite is essentially a female that makes sperm for a brief period before oogenesis. Sex determination in C. elegans is controlled by a pathway of autosomal regulatory genes, the state of which is determined by the X:A ratio. One of these genes, tra-2, is required for hermaphrodite development, but not for male development, because null mutations in tra-2 masculinize XX animals but have no effect on XO males. Dominant, gain-of-function tra-2 mutations have now been isolated that completely feminize the germline of XX animals so that they make only oocytes and no sperm and, thus, are female. Most of the tra-2(dom) mutations do not correspondingly feminize XO animals, so they do not appear to interfere with control by her-1, a gene thought to negatively regulate tra-2 in XO animals. Thus, these mutations appear to cause gain of tra-2 function in the XX animal only. Dosage studies indicate that 5 of 7 tra-2(dom) alleles are hypomorphic, so they do not simply elevate XX tra-2 activity overall. These properties suggest that in the wild type, tra-2 activity is under two types of control: (1) in males, it is inactivated by her-1 to allow male development to occur, and (2) in hermaphrodites, tra-2 is active but transiently inactivated by another, unknown, regulator to allow hermaphrodite spermatogenesis; this mode of regulation is hindered by the tra-2(dom) mutations, thereby resulting in XX females.
GENETIC REGULATION OF SN-GLYCEROL-3-PHOSPHATE DEHYDROGENASE IN BROWN ADIPOSE TISSUE
Authors: Cook Jeffry R , Stadler Ulrike , Burkart Donna , Kozak Leslie P 
Published: January 2021

ABSTRACT
The levels of sn-glycerol-3-phosphate dehydrogenase (GPDH) were determined in the brown adipose tissue (BAT) of different inbred strains of mice. The BAT of the BALB/cJ strain contains twice as much enzyme activity per milligram protein as do other strains. The appearance of this difference is developmentally dependent, since it is not detected in BAT until 25-30 days postpartum. Genetic analysis of this strain difference has shown that the mechanism of inheritance involves at least two genes, one of which is linked to the Gdc-1 structural locus on chromosome 15. Determinations of GPDH synthesis by immunoprecipitation of GPDH protein labeled in vivo with [3H]leucine, and of GPDH mRNA by Northern blot analysis, establish that in BALB/cJ mice higher rates of enzyme synthesis are determined by elevated levels of GPDH mRNA. It was also found that cold stress increases GPDH mRNA levels in all the strains examined.
THE RELATIONSHIP BETWEEN THE FUNCTIONAL COMPLEXITY AND THE MOLECULAR ORGANIZATION OF THE ANTENNAPEDIA LOCUS OF DROSOPHILA MELANOGASTER
Authors: Abbott Michael K , Kaufman Thomas C 
Published: January 2021

ABSTRACT
The Antp locus is involved in the development of the thorax of the larval and adult Drosophila. The absence of Antp + function during embryogenesis results in the larval mesothorax exhibiting characteristics of the prothorax and an ensuing lethality; the loss of Antp + function in the development of the adult thorax causes specific portions of the leg, wing and humeral imaginal discs to develop abnormally. Every Antp mutation, however, does not cause all of these developmental defects. Certain mutant alleles disrupt humeral and wing disc development without affecting leg development, and they are not deficient for the wild-type function required during embryogenesis. Other Antp mutations result in abnormal legs, but do not alter dorsal thoracic development. Mutations of each type can complement to produce a normal adult fly, which suggests that there are at least two discrete functional units within the locus. This hypothesis is supported by the fact that each of the developmental defects arises from the alteration of a different physical region within the Antp DNA. These observations indicate that the complete developmental role of the Antp locus is defined by the spatial and temporal regulation of the expression of several individual functional units.
INHERITANCE OF MUTATOR ACTIVITY IN ZEA MAYS AS ASSAYED BY SOMATIC INSTABILITY OF THE bz2-mu1 ALLELE
Authors: Walbot Virginia 
Published: January 2021

ABSTRACT
Mutator lines of maize were originally defined by their high forward mutation rate, now known to be caused by the transposition of numerous Mu elements. A high frequency of somatic instability, seen as a fine purple spotting pattern on the aleurone tissue, is characteristic of Mu-induced mutable alleles of genes of the anthocyanin pathway. Loss of such somatic instability has been correlated with the de novo, specific modification of Mu element DNA. In this report the presence or loss of somatic instability at the bz2-mu1 allele has been monitored to investigate the inheritance of the Mutator phenomenon. The active state is labile and may become weakly active (low fraction of spotted kernel progeny) or totally inactive (no spotted kernel progeny) during either outcrossing to non-Mutator lines or on self-pollination. In contrast, the inactive state is relatively permanent with rare reactivation in subsequent crosses to non-Mutator lines. Cryptic bz2-mu1 alleles in weakly active lines can be efficiently reactivated to somatic instability when crossed with an active line. However, in reciprocal crosses of active and totally inactive individuals, strong maternal effects were observed on the inactivation of a somatically unstable bz2-mu1allele and on the reactivation of cryptic bz2-mu1 alleles. In general, the activity state of the female parent determines the mutability of the progeny.
Optimal Recombination Rate in Fluctuating Environments
Authors: Sasaki Akira , Iwasa Yoh 
Published: January 2021

ABSTRACT
The optimal recombination rate which maximizes the long-term geometric average of the population fitness is studied for a two-locus haploid model, assuming that the fitnesses of genotypes AB, Ab, aB and ab are 1 + s(t), 1 - s(t), 1 - s(t), and 1 + s(t), respectively, where s(t) follows various stationary stochastic processes with the average zero. With positive recombination, the polymorphism is stably maintained at both loci. After an initial transient phase, the dynamics are reduced to one dimension, and are analyzed for (i) weak selection limit, (ii) strong selection limit, and (iii) selection with two state Markovian jump. Results are: (1) If the environmental fluctuation has a predominant periodic component, r opt is approximately inversely proportional to the period irrespective of selection intensity. (2) If the fluctuation is a superposition of many periodic components, the one with the longest period is the most effective in determining r opt because the genetic dynamics cannot track very quick fluctuations (low pass filter effect). (3) If the power spectrum density is decreasing with the frequency, as in pink, or 1/f noises, r opt is small when selection is weak, and increases with the selection intensity. Numerical calculation of the genetic dynamics of a recombination modifier supports all these predictions for the evolutionarily stable recombination rate.
Behavioral and Cytogenetic Analysis of the cacophony Courtship Song Mutant and Interacting Genetic Variants in Drosophila melanogaster
Authors: Kulkarni Shankar J , Hall Jeffrey C 
Published: January 2021

ABSTRACT
The courtship song of a Drosophila melanogaster male consists of tone pulses interspersed with humming sounds. An X chromosomal mutation, cacophony (cac), causes the production of polycyclic pulses readily distinguishable from those in wild type, which are mono- or bicyclic. Yet, courtship hums and flight wing beats are normal in this mutant, suggesting a specific role of the cac gene in the neural program underlying one particular feature of the fly's wing vibrations. A precise cytogenetic localization of cac is presented; this was obtained by uncovering the song abnormality with deletions that are missing all or the distal part of region 11A; the flies tested were diplo-X adults that had been turned into males by the transformer mutation. Duplications including distal 11A covered cac. The possibility of behavioral specificity for cac's effects was examined by screening a variety of sexual and nonsexual behaviors; these experiments included tests of flies in which the mutation was uncovered by a small deletion. We conclude that cac causes only a limited array of well-defined defects: longer and louder tone pulses in the song and depressed locomotor activity. Further complementation tests involving cac and other closely linked genetic variants-the night-blind-A (nbA) visual mutation, l(1) L13 lethal mutations, and a series of X chromosomal breakpoints-suggested complex interactions among these factors: the breakpoints uncover all three types of mutations; cac and nbA appear to be alleles of l(1)L13, whereas the two behavioral mutations complement each other
Cytogenetics of Notch Mutations Arising in the Unstable X Chromosome Uc of Drosophila melanogaster
Authors: Johnson-Schlitz Dena , Lim J K 
Published: January 2021

ABSTRACT
A derivative of the unstable X chromosome, Uc, isolated in 1978 is still unstable and exhibits most of the genetic properties characteristic of the original Uc. This derivative, Df(1)cm-In, contains an inversion of the genes between bands 6F1-2 and 3D3-5 and a lethal deficiency between 6D5-7 and 6F1-2. This chromosome generated Notch mutations at a rate of 3.47 ± 0.32% during seven consecutive generations. Cytological analysis of 50 Notch mutations of independent origin in the Df(1)cm-In chromosome showed that all of the 50 had an apparently identical deletion involving the region between 3D3-5 and 3C7-8 of the X chromosome. The results of in situ hybridization indicated that the extent of deletion in all of the 20 Notch deficiencies sampled from the 50 mentioned above involves about 10 kb of the sequences from the 3′ end of the Notch locus. In addition to hypermutability and the accumulation of site-specific chromosome breaks, the Df(1)cm-In chromosome reinverts its inversion to the normal sequence and exhibits use of the existing chromosome breakpoints to generate new rearrangements.
On the Overdispersed Molecular Clock
Authors: Takahata Naoyuki 
Published: January 2021

ABSTRACT
Rates of molecular evolution at some loci are more irregular than described by simple Poisson processes. Three situations under which molecular evolution would not follow simple Poisson processes are reevaluated from the viewpoint of the neutrality hypothesis: (i) concomitant or multiple substitutions in a gene, (ii) fluctuating substitution rates in time caused by coupled effects of deleterious mutations and bottlenecks, and (iii) changes in the degree of selective constraints against a gene (neutral space) caused by successive substitutions. The common underlying assumption that these causes are lineage nonspecific excludes the case where mutation rates themselves change systematically among lineages or taxonomic groups, and severely limits the extent of variation in the number of substitutions among lineages. Even under this stringent condition, however, the third hypothesis, the fluctuating neutral space model, can generate fairly large variation. This is described by a time-dependent renewal process, which does not exhibit any episodic nature of molecular evolution. It is argued that the observed elevated variances in the number of nucleotide or amino acid substitutions do not immediately call for positive Darwinian selection in molecular evolution.