bluuebunny/crossref_metadata_2025_split huggingface dataset:
LINKAGE RELATIONSHIPS OF NINE ENZYME LOCI IN SUNFISHES (LEPOMIS; CENTRARCHIDAE)
Authors: Pasdar Manijeh , Philipp David P , Whitt Gregory S 
Published: January 2021

ABSTRACT
Linkage relationships of nine enzyme loci; aconitase (Acon), esterase (Est), glucosephosphate isomerase A and B (Gpi), glycerate-2-dehydrogenase (G2dh), malic enzyme (Me), phosphoglycerate kinase (Pgk), phosphoglucomutase (Pgm) and superoxide dismutase (Sod), were investigated in sunfishes (Lepomis, Centrarchidae). Reciprocal F1 hybrids produced from crosses between green sunfish (Lepomis cyanellus) and redear sunfish (L. microlophus) were backcrossed with each of the two parental species. A three-point linkage map comprising G2dh, Pgk and Sod is reported. The frequencies of recombination between G2dh and Pgk and between Pgk and Sod are estimated as 45.3 and 24.7%. The remaining six loci assort independently. Possible linkage conservation and homology of this linkage group with those of other vertebrate species are discussed.
GENETICS OF CHLAMYDOMONAS REINHARDTII DIPLOIDS. II. THE EFFECTS OF DIPLOIDY AND ANEUPLOIDY ON THE TRANSMISSION OF NON-MENDELIAN MARKERS
Authors: Eves Eva M , Chiang Kwen-Sheng 
Published: January 2021

ABSTRACT
The transmission of two non-Mendelian drug resistance markers has been studied in crosses of Chlamydomonas reinhardtii involving diploids and aneuploids with different mating type genotypes. Under normal laboratory conditions for gametogenesis, mating and zygote maturation, the transmission pattern of the non-Mendelian markers sr-u-1 (resistance to streptomycin) and spr-u-1-27-3 (resistance to spectinomycin) is primarily determined by the mating type genotypes of the parental cells. Our results confirm and expand an earlier observation suggesting that an apparent codominant function of the female (mt +) allele in regulating chloroplast gene transmission in meiosis appears to be distinct and separate from its recessive function in regulating mating behavior. The chloroplast DNA complement (as indexed by the number of extranuclear DNA-containing bodies) may exert a secondary effect on the transmission of these markers. Within a mating type group (mt+/mt- or mt-/mt-) a cell line with more chloroplast DNA tended to transmit its non-Mendelian markers more frequently than a cell line with less chloroplast DNA.
DEVIATIONS FROM HARDY-WEINBERG PROPORTIONS: SAMPLING VARIANCES AND USE IN ESTIMATION OF INBREEDING COEFFICIENTS
Authors: Robertson Alan , Hill William G 
Published: January 2021

ABSTRACT
An analysis is made of the distribution of deviations from Hardy-Weinberg proportions with k alleles and of estimates of inbreeding coefficients (f) obtained from these deviations.—If f is small, the best estimate of f in large samples is shown to be 2∑i(Tii/Ni)/(k - 1), where Tii is an unbiased measure of the excess of the ith homozygote and Ni the number of the ith allele in the sample [frequency = Ni/(2N)]. No extra information is obtained from the Tij, where these are departures of numbers of heterozygotes from expectation. Alternatively, the best estimator can be computed from the Tij, ignoring the Tii. Also (1) the variance of the estimate of f equals 1/(N(k - 1)) when all individuals in the sample are unrelated, and the test for f = 0 with 1 d.f. is given by the ratio of the estimate to its standard error; (2) the variance is reduced if some alleles are rare; and (3) if the sample consists of full-sib families of size n, the variance is increased by a proportion (n - 1)/4 but is not increased by a half-sib relationship.—If f is not small, the structure of the population is of critical importance. (1) If the inbreeding is due to a proportion of inbred matings in an otherwise random-breeding population, f as determined from homozygote excess is the same for all genes and expressions are given for its sampling variance. (2) If the homozygote excess is due to population admixture, f is not the same for all genes. The above estimator is probably close to the best for all f values.
ISOLATION OF ANEUPLOID-GENERATING MUTANTS OF ASPERGILLUS NIDULANS, ONE OF WHICH IS DEFECTIVE IN INTERPHASE OF THE CELL CYCLE
Authors: Upshall A , Mortimore I D 
Published: January 2021

ABSTRACT
A method is described for isolating mutants potentially defective in loci involved in mitotic chromosome segregation. Conditional lethal, heat-sensitive (42°) mutants were assayed at a subrestrictive temperature of 37° for an inflated production of colonies displaying phenotypes and behavior patterns of whole chromosome aneuploids. Of 14 mutants, three showed specificity for one disomic phenotype, whereas 11 generated colonies mosaic for different aneuploid phenotypes. This latter group is designated hfa (high frequency of aneuploid). For ten of the 11 mutants temperature sensitivity and aneuploid production cosegregated, indicating a single mutation in each. These mutations were recessive and nonallelic. Analysis was concentrated on the hfaB3 mutation which is mapped to chromosome VI tightly linked to the methB and tsB loci. The disruptive influence of hfaB3 on mitosis at 37° was shown by (1) ploidy and whole chromosome-type segregation of markers in the breakdown sectors of phenotypically aneuploid colonies obtained from multiply marked homozygous hfaB3 disploids; (2) a high frequency of haploid and nondisjunctional diploid segregants among spontaneous yellow-spored parasexual recombinants taken from green-spored homozygous hfaB3 diploids. The mutation had no effect on meiotic chromosome segregation at 37°. The single interphase nucleus in germlings at 42°, coupled with changes in the mitotic index in temperature exchange experiments, showed hfaB3 to arrest the cell cycle in interphase at restrictive temperature. A conclusion drawn is that the hfaB gene product is required both for entry into mitosis and for normal chromosome segregation in dividing nuclei.
MULTIPLE-LOCUS HETEROZYGOSITY AND THE PHYSIOLOGICAL ENERGETICS OF GROWTH IN THE COOT CLAM, MULINIA LATERALIS, FROM A NATURAL POPULATION
Authors: Garton David W , Koehn Richard K , Scott Timothy M 
Published: January 2021

ABSTRACT
The relationship between individual energy budgets and multiple-locus heterozygosity at six polymorphic enzyme loci was examined in Mulinia lateralis. Energy budgets were determined by measuring growth rates, rates of oxygen consumption, ammonia excretion and clearance rates. Enzyme genotypes were determined using starch gel electrophoresis. Growth rate and net growth efficiency (the ratio of energy available for growth to total energy absorbed) increased with individual heterozygosity. The positive relationship between observed growth and multiple-locus heterozygosity was associated with a negative relationship between routine metabolic costs and increasing heterozygosity. Reduction in routine metabolic costs explained 60% of the observed increased growth of more heterozygous individuals. When routine metabolic costs were standardized for differences in feeding rates, these standard metabolic costs explained 97% of the differences in growth rate. Lower standard metabolic costs, associated with increasing heterozygosity, have been proposed as a physiological mechanism for the relationship between multiple-locus heterozygosity and growth rate that has been reported for a variety of organisms, ranging in diversity from aspens to humans. This study demonstrates that reduction of standard metabolic costs, at least in clams, accounts for virtually all of the differences in growth rate among individuals of differing heterozygosity.
MUTANTS WITH ALTERED Ca2+-CHANNEL PROPERTIES IN PARAMECIUM TETRAURELIA: ISOLATION, CHARACTERIZATION AND GENETIC ANALYSIS
Authors: Hinrichsen Robert D , Saimi Yoshiro , Kung Ching 
Published: January 2021

ABSTRACT
Dancers are a group of mutants in Paramecium tetraurelia whose Ca2+ current inactivates poorly and are likely to be defective in the structure of their Ca2+ channels. These mutants show prolonged backward swimming in response to K+ and Ba2+ in the medium and were selected by this property in a galvanotactic trough. The dancer mutants are semidominant, and all isolated mutants belong to one complementation group; they are not allelic to any of the previously isolated behavioral mutants of P. tetraurelia. The phenotypic change from the homozygous parent to heterozygous F1 generation takes three to five fissions. There is no evidence of a cytoplasmic factor capable of converting the dancer to the wild-type phenotype, as has been demonstrated in the mutants pawn and cnr. We suggest that the dancer locus is a structural gene for the Ca2+ channel.
DEVELOPMENTAL GENETICS OF THE 2E-F REGION OF THE DROSOPHILA X CHROMOSOME: A REGION RICH IN "DEVELOPMENTALLY IMPORTANT" GENES
Authors: Perrimon Norbert , Engstrom Lee , Mahowald Anthony P 
Published: January 2021

ABSTRACT
We have analyzed the 2E1-3A1 area of the X chromosome with special attention to loci related to embryogenesis. Published maps indicate that this chromosomal segment contains ten bands. Our genetic analysis has identified 11 complementation groups: one recessive visible (prune), two female steriles and eight lethals. One of the female sterile loci is fs(1)k10 for which homozygous females produce both egg chambers and embryos with a dorsalized morphology. The second female sterile is the paternally rescuable fs(1) pecanex in which unrescued embryos have a hypertrophic nervous system. Of the eight lethal complementation groups two are recessive embryonic lethals: hemizygous giant (gt) embryos possess segmental defects, and hemizygous crooked neck (crn) embryos exhibit a twisted phenotype. Analysis of these mutations in the female germ line indicates that gt does not show a maternal effect, whereas normal activity of crn is required for germ cell viability. Analysis of the maternal effect in germ line clones of the remaining six recessive lethal complementation groups indicates that four are required for germ cell viability and one produces ambiguous results for survival of the germ cells. The remaining, l(1) pole hole, is a recessive early pupal lethal in which embryos derived from germ line clones and lacking wild-type gene activity exhibit the "torso" or "pole hole" phenotype.
STUDIES ON THE MECHANISM OF HETEROCHROMATIC POSITION EFFECT AT THE ROSY LOCUS OF DROSOPHILA MELANOGASTER
Authors: Rushlow C A , Bender W , Chovnick A 
Published: January 2021

ABSTRACT
Experiments are described that extend the characterization of position effect variants of the rosy locus and test possible mechanisms of heterochromatic position effect.—Rosy position effect variants exhibit a variegated phenotype with respect to xanthine dehydrogenase activity in malpighian tubules.—The breakpoints of the position effect mutations are located on the DNA map of the rosy region outside of the rosy locus DNA; ryps 1136 is located in the DNA of the l(3)S12 gene immediately proximal to rosy, whereas ryps 1149 is located some 15 kb distal to rosy in the pic locus.—Southern blot experiments are described that test and reject the notion that heterochromatic position effect results from underreplication of the position-affected gene. Rather, the results of Northern blots serve to direct attention to position effect as a defect in transcription.—Histone region deletion heterozygosity and butyrate-feeding experiments failed to exhibit specific suppression of position effect at the rosy locus.
INHERITANCE OF ADRENAL PHENYLETHANOLAMINE N-METHYLTRANSFERASE ACTIVITY IN THE RAT
Authors: Stolk Jon M , Vantini Guido , Guchhait Ras B , Hurst Jeffrey H , Perry Bruce D , U'Prichard David C , Elston Robert C 
Published: January 2021

ABSTRACT
Phenylethanolamine N-methyltransferase (PNMT) is the enzyme that catalyzes the S-adenosyl-l-methionine-dependent methylation of (-)norepinephrine to (-)epinephrine in the adrenal medulla. Adrenal PNMT activity is markedly different in two highly inbred rat strains; enzyme activity in the F344 strain is more than fivefold greater than that in the Buf strain. Initial characterization of the enzyme in the two inbred strains reveals evidence for catalytic and structural differences, as reflected in dissimilar K m values for the cosubstrate (S-adenosyl-l-methionine) and prominent differences in thermal inactivation curves. To assess adrenal PNMT activity in an F344 × Buf pedigree, we employed a statistical procedure to test for one- and two-locus hypotheses in the presence of within-class correlations due to cage or litter effects. The PNMT data in the pedigree are best accounted for by segregation at a simple major locus superimposed upon a polygenic background; data obtained from the biochemical studies suggest that the major locus is a structural gene locus.
CHARACTERIZATION OF A RECOMBINANT MOUSE t HAPLOTYPE THAT EXPRESSES A DOMINANT LETHAL MATERNAL EFFECT
Authors: Winking Heinz , Silver Lee M 
Published: January 2021

ABSTRACT
The twLub 2 chromosome was generated by rare recombination between a complete t haplotype and a wild-type form of mouse chromosome 17. This recombinant chromosome expresses a dominant lethal effect in all embryos that inherit the mutant chromosome from their mothers. The phenotype of this maternal effect is indistinguishable from that expressed by the previously described Thp deletion chromosome. It appears likely that the crossing over event that gave rise to twLub 2 was unequal and resulted in the alteration or deletion of a gene (which is named the T-associated maternal effect locus, Tme) that must be inherited from the mother in order for normal development to proceed through late stages of gestation. The results presented here allow a mapping of the Tme locus between the quaking and tufted loci which are 3 cM apart within the proximal region of chromosome 17.
LOCATION OF THE GENES THAT CONTROL INDUCTION OF THE ALLANTOIN-DEGRADING ENZYMES IN SACCHAROMYCES CEREVISIAE
Authors: Turoscy Vanessa , Chisholm George , Cooper Terrance G 
Published: January 2021

ABSTRACT
In an effort to understand the regulation of allantoin degradation in Saccharomyces cerevisiae, we isolated two classes of mutants, each defective in the induction process associated with production of the pathway enzymes. Mutation at one locus (DAL80) results in constitutive expression of the genes involved in allantoin catabolism. Mutation at the second locus (DAL-81) results in the loss of ability to induce these enzymes. This report describes genetic data indicating that the DAL80 and DAL81 loci are situated approximately 13 cM from the centromere on the right arm of chromosome XI and 9 cM proximal to the DAL1 locus on chromosome IX, respectively.
DYSGENESIS-INDUCED INSTABILITY OF ROSY LOCUS TRANSFORMATION IN DROSOPHILA MELANOGASTER: ANALYSIS OF EXCISION EVENTS AND THE SELECTIVE RECOVERY OF CONTROL ELEMENT DELETIONS
Authors: Daniels Stephen B , McCarron Margaret , Love Carol , Chovnick Arthur 
Published: January 2021

ABSTRACT
Utilizing the method of P-M hybrid dysgenesis-mediated gene transfer to insert rosy locus DNA into various chromosomal locations, we recovered a transformed strain that carries an ry + transposon inserted in or near the scalloped locus in polytene section 13F on the Χ chromosome. The resultant product, when stabilized, behaves as a homozygous and hemizygous viable and fertile extreme scalloped allele associated with wild-type expression of the rosy locus. We have labeled this allele, sdry+ +. This allele has been destabilized by subsequent P-M hybrid dysgenesis, and mutations were recovered that exhibit alterations in the rosy and/or scalloped phenotypes. Representative samples of all phenotypic classes have been characterized by Southern blot analyses of restricted DNA. The most common events are excisions of DNA wholly internal to the transposon and representing sections of rosy DNA. In addition to loss of rosy locus function, such excisions affect the scalloped locus expression.—A second dysgenesis experiment was carried out involving an ry + transposon inserted in polytene section 16D on the Χ chromosome. A minimal estimate of the relative frequency of imprecise excisions, determined in this experiment is 75%.—A successful pilot experiment is described that utilizes dysgenic perturbation of the sdryry + allele to select for small deletions of the 5' noncoding region of the rosy locus.
MUTAGENESIS IN CAENORHABDITIS ELEGANS. II. A SPECTRUM OF MUTATIONAL EVENTS INDUCED WITH 1500 R OF γ-RADIATION
Authors: Rosenbluth Raja E , Cuddeford Cheryl , Baillie David L 
Published: January 2021

ABSTRACT
We previously established a γ-ray dose-response curve for recessive lethal events (lethals) captured over the eT1 balancer. In this paper we analyze the nature of lethal events produced, with a frequency of 0.04 per eT1 region, at a dose of 1500 r. To do so, we developed a protocol that, in the absence of cytogenetics, allows balanced lethals to be analyzed for associated chromosomal rearrangements. A set of 35 lethal strains was chosen for the analysis. Although the dosage was relatively low, a large number of multiple-break events were observed. The fraction of lethals associated with rearrangements was found to be 0.76. Currently most X- and γ-ray dosages used for mutagenesis in C. elegans are 6000-8000 r. From our data we conservatively estimated that 43% of rearrangements induced with 8000 r would be accompanied by additional chromosome breaks in the genome. With 1500 r the value was 5%.—The 35 lethals studied were derived from 875 screened F1's. Among these lethals there were (1) at least two unc-36 duplications, (2) at least four translocations, (3) at least six deficiencies of chromosome V (these delete about 90% of the unc-60 to unc-42 region) and (4) several unanalyzed rearrangements. Thus, it is possible to recover desired rearrangements at reasonable rates with a dose of only 1500 r.—We suggest that the levels of ionizing radiation employed in most published C. elegans studies are excessive and efforts should be made to use reduced levels in the future.
MECHANISMS OF SPONTANEOUS AND INDUCED FRAMESHIFT MUTATION IN BACTERIOPHAGE T4
Authors: Streisinger George , Owen Joyce Emrich 
Published: January 2021

ABSTRACT
Frequencies of spontaneous and proflavine-induced frameshift mutations increase dramatically as a function of the number of reiterated base pairs at each of two sites in the lysozyme gene of bacteriophage T4. At each site, proflavine induces addition mutations more frequently than deletion mutations. We confirm that the steroidal diamine, irehdiamine A, induces frameshift addition mutations. At sites of reiterated bases, we propose that base pairing is misaligned adjacent to a gap. The misaligned configuration is stabilized by the stacking of mutagen molecules around the extrahelical base, forming a sandwich. Proflavine induces addition mutations efficiently at a site without any reiterated bases. Mutagenesis at such sites may be due to mutagen-induced stuttering of the replication complex.
SEQUENCE EVOLUTION OF DROSOPHILA MITOCHONDRIAL DNA
Authors: Wolstenholme David R , Clary Douglas O 
Published: January 2021

ABSTRACT
We have compared nucleotide sequences of corresponding segments of the mitochondrial DNA (mtDNA) molecules of Drosophila yakuba and Drosophila melanogaster, which contain the genes for six proteins and seven tRNAs. The overall frequency of substitution between the nucleotide sequences of these protein genes is 7.2%. As was found for mtDNAs from closely related mammals, most substitutions (86%) in Drosophila mitochondrial protein genes do not result in an amino acid replacement. However, the frequencies of transitions and transversions are approximately equal in Drosophila mtDNAs, which is in contrast to the vast excess of transitions over transversions in mammalian mtDNAs. In Drosophila mtDNAs the frequency of C ↔ T substitutions per codon in the third position is 2.5 times greater among codons of two-codon families than among codons of four-codon families; this is contrary to the hypothesis that third position silent substitutions are neutral in regard to selection. In the third position of codons of four-codon families transversions are 4.6 times more frequent than transitions and A ↔ T substitutions account for 86% of all transversions. Ninety-four percent of all codons in the Drosophila mtDNA segments analyzed end in A or T. However, as this alone cannot account for the observed high frequency of A ↔ T substitutions there must be either a disproportionately high rate of A ↔ T mutation in Drosophila mtDNA or selection bias for the products of A ↔ T mutation.—Consideration of the frequencies of interchange of AGA and AGT codons in the corresponding D. yakuba and D. melanogaster mitochondrial protein genes provides strong support for the view that AGA specifies serine in the Drosophila mitochondrial genetic code.
GENETIC DIFFERENTIATION OF TRANSPOSABLE ELEMENTS UNDER MUTATION AND UNBIASED GENE CONVERSION
Authors: Slatkin Montgomery 
Published: January 2021

ABSTRACT
A model is developed to predict the extent of genetic differentiation in a family of transposable elements under the combined effects of genetic drift, transposition, mutation and unbiased gene conversion. The model is based on simplifying assumptions that are valid when transposition is always to new sites and copy number per site is low. In the absence of gene conversion, the degree of differentiation as measured by the probability of identity of different elements is the same as at a single locus with the same mutation rate but in a population of effective size Nc/2, where N is the population size and c is the number of copies per individual. The inclusion of unbiased gene conversion does not significantly change this result. If, as seems to be the case, families of transposable elements are relatively homogeneous, then the model implies either that mutation rates for transposable elements are much lower than at comparable single-copy loci or that some other force, such as natural selection or biased gene conversion, is at work. Transposition is a very ineffective force for homogenizing a family of transposable elements.
SUPPRESSION OF THE FACET-STRAWBERRY POSITION EFFECT IN DROSOPHILA BY LESIONS ADJACENT TO NOTCH
Authors: Welshons W J , Welshons H J 
Published: January 2021

ABSTRACT
The recessive visible rough eye mutant effect of faswb, a small deletion at the 5' end of the Notch locus, is suppressed when faswb is coupled to five different closely linked deficiencies distal to salivary band 3C7. In addition, an inversion with a proximal breakpoint between 3C3 and 3C5 similarly suppresses the mutant effect. The data support the position effect interpretation of faswb: The small deletion allows functions distal to Notch to interfere with functions at Notch, and when the interference is eliminated, the faswb-mutant effect disappears.—The faswb deletion also interacts with another recessive visible rough-eye mutant at Notch called fag. In the cis condition, faswb fag double mutants have a mutant-eye phenotype like fag (similar to the mutant effect of faswb) and, in addition, express an accessory phenotype (thickened wing veins). Although the mutant-eye effect of faswb can be suppressed by lesions adjacent to Notch, the accessory phenotype of the coupled mutants is not suppressed. It is suggested that the faswb deletion has two observable effects: One is a modifiable position effect causing the faswb rough-eye phenotype; the other is a stable effect exerted upon a 5-kb insertion that is the probable cause of the fag mutant expression, thus resulting in a wing effect that accompanies the eye effect of fag.