bluuebunny/crossref_metadata_2025_split huggingface dataset:
NOVEL NEMATODE AMBER SUPPRESSORS
Authors: Hodgkin Jonathan 
Published: January 2021

ABSTRACT
Nine amber suppressor mutations were isolated in the nematode Caenorhabditis elegans by reverting amber alleles of a sex-determining gene, tra-3. One suppressor maps to a known locus, sup-5 III, but the other eight map to three new loci, sup-21 X (five alleles), sup-22 IV (two alleles) and sup-23 IV (one allele). Amber alleles of tra-3 and of a dumpy gene, dpy-20, were used to measure the efficiency of suppression; the sup-21 and the sup-22 alleles were both shown to be heterogeneous and generally weaker suppressors than sup-5 alleles, which are homogeneous. The spectrum of mutations suppressed by a strong sup-21 allele, e1957, was investigated and compared to the spectra for the amber suppressors sup-5 III and sup-7 X, using amber alleles in 13 assorted genes. Some of the differences between these spectra may be due to limited tissue specificity in sup-21 expression.—Suppression of dpy-20 was used to show that the sex-linked suppressors sup-7 and sup-21 are not dosage compensated in male (XO) relative to hermaphrodite (XX).—Several uses of amber suppressors are critically discussed: for identifying null mutations, for varying levels of gene activity and for detecting maternal mRNA.
ELEVATED LEVELS OF PETITE FORMATION IN STRAINS OF SACCHAROMYCES CEREVISIAE RESTORED TO RESPIRATORY COMPETENCE. I. ASSOCIATION OF BOTH HIGH AND MODERATE FREQUENCIES OF PETITE MUTANT FORMATION WITH THE PRESENCE OF ABERRANT MITOCHONDRIAL DNA
Authors: Evans R J , Oakley K M , Clark-Walker G D 
Published: January 2021

ABSTRACT
When recently arisen spontaneous petite mutants of Saccharomyces cerevisiae are crossed, respiratory competent diploids can be recovered. Such restored strains can be divided into two groups having sectored or unsectored colony morphology, the former being due to an elevated level of spontaneous petite mutation. On the basis of petite frequency, the sectored strains can be subdivided into those with a moderate frequency (5-16%) and those with a high frequency (&gt;60%) of petite formation. Each of the three categories of restored strains can be found on crossing two petites, suggesting either that the parental mutants contain a heterogeneous population of deleted mtDNAs at the time of mating or that different interactions can occur between the defective molecules. Restriction endonuclease analysis of mtDNA from restored strains that have a wild-type petite frequency showed that they had recovered a wild-type mtDNA fragmentation pattern. Conversely, all examined cultures from both categories of sectored strains contained aberrant mitochondrial genomes that were perpetuated without change over at least 200 generations. In addition, sectored colony siblings can have different aberrant mtDNAs. The finding that two sectored, restored strains from different crosses have identical but aberrant mtDNAs provides evidence for preferred deletion sites from the mitochondrial genome. Although it appears that mtDNAs from sectored strains invariably contain duplications, there is no apparent correlation between the size of the duplication and spontaneous petite frequency.
ELEVATED LEVELS OF PETITE FORMATION IN STRAINS OF SACCHAROMYCES CEREVISIAE RESTORED TO RESPIRATORY COMPETENCE. II. ORGANIZATION OF MITOCHONDRIAL GENOMES IN STRAINS HAVING HIGH AND MODERATE FREQUENCIES OF PETITE MUTANT FORMATION
Authors: Evans R J , Clark-Walker G D 
Published: January 2021

ABSTRACT
Restriction enzyme analysis of aberrant mtDNA molecules in restored strains of Saccharomyces cerevisiae that display an elevated level of petite formation has shown the occurrence of novel junction fragments and nonstoichiometric amounts for some unaltered bands. Five aberrant mitochondrial genomes from high-frequency petite-forming (hfp) strains (&gt;60% petites per generation) contain like-oriented duplications and single copy regions. High-frequency petite formation is postulated to arise from increased intramolecular recombination between duplicated segments. Mitochondrial DNA structures in two other hfp strains cannot be easily interpreted and might arise from intramolecular recombination.—Mitochondria DNA from moderate-frequency petite-forming (mfp) strains (5-16% petites per generation) contains inverted duplications in two cases. The elevated petite formation is postulated to arise from homologous recombination between directly repeated sequences. In mtDNA from one mfp strain, deletion end-points have been shown to overlap. Such deletion endpoint overlap is postulated to be required for the maintenance of the tandem duplication in hfp strains. Two regions of the wild-type mtDNA (between cyb and oli2 and between SrRNA and oxi2) appear to be dispensable for mitochondrial function.
THE MOLECULAR THROUGH ECOLOGICAL GENETICS OF ABNORMAL ABDOMEN IN DROSOPHILA MERCATORUM. I. BASIC GENETICS
Authors: Templeton Alan R , Crease Teresa J , Shah Faith 
Published: January 2021

ABSTRACT
The abnormal abdomen syndrome (aa) in Drosophila mercatorum is characterized by the persistence of juvenilized cuticle on the adult abdomen. The aa phenotype is shown to depend on at least two X-linked genetic elements that are about one map unit apart near the centromeric end of the X chromosome. These two genetic elements are necessary for aa expression; one behaves as a dominant element and the other as a recessive. Overlaying these genetic studies upon molecular work reported elsewhere, it is argued that the dominant element is the presence of a 5 kb insertion in a majority of the X-linked repeats coding for the 28S ribosomal RNA. The recessive element appears to be a locus controlling differential replication of noninserted over inserted 28S genes during polytenization. The aa syndrome requires both the presence of the inserted repeats and the failure to preferentially amplify noninserted repeats. Given the necessary X-linked elements for aa, a variety of modifiers are revealed. First, aa expression in males is Y-linked, apparently corresponding to a deletion of the 18S/28S rDNA gene cluster normally found on the Y. Moreover, all major autosomes can modify the penetrance of aa.
SHORT GENE CONVERSIONS IN THE HUMAN FETAL GLOBIN GENE REGION: A BY-PRODUCT OF CHROMOSOME PAIRING DURING MEIOSIS?
Authors: Powers Patricia A , Smithies Oliver 
Published: January 2021

ABSTRACT
DNA sequence comparisons of a 1200-base pair (bp) region in 14 human fetal globin genes in seven linked pairs reveal 31 nucleotide substitutions at positions where the fetal globin genes, G y and A y, usually differ. In each case, the newly substituted nucleotide is identical to the one found at the same position in the linked nonallelic gene. Most of these nucleotide substitutions are clearly the result of gene conversions, but 11 could be the result of either very short gene conversions or of point mutations. The unexpectedly frequent occurrence of these short gene conversions suggests that they may be the relics of some normal interaction between homologous but nonallelic DNA sequences, and we discuss the possibility that they result from interactions occurring between homologous sequences during the process of meiotic chromosome pairing.
MITOCHONDRIAL DNA SEQUENCE DIVERGENCE AMONG LYCOPERSICON AND RELATED SOLANUM SPECIES
Authors: McClean Phillip E , Hanson Maureen R 
Published: January 2021

ABSTRACT
Sequence divergence among the mitochondrial (mt) DNA of nine Lycopersicon and two closely related Solanum species was estimated using the shared fragment method. A portion of each mt genome was highlighted by probing total DNA with a series of plasmid clones containing mt-specific DNA fragments from Lycopersicon pennellii. A total of 660 fragments were compared. As calculated by the shared fragment method, sequence divergence among the mtDNAs ranged from 0.4% for the L. esculentum-L. esculentum var. cerasiforme pair to 2.7% for the Solanum rickii-L. pimpinellifolium and L. cheesmanii-L. chilense pairs. The mtDNA divergence is higher than that reported for Lycopersicon chloroplast (cp) DNA, which indicates that the DNAs of the two plant organelles are evolving at different rates. The percentages of shared fragments were used to construct a phenogram that illustrates the present-day relationships of the mtDNAs. The mtDNA-derived phenogram places L. hirsutum closer to L. esculentum than taxonomic and cpDNA comparisons. Further, the recent assignment of L. pennellii to the genus Lycopersicon is supported by the mtDNA analysis.
FRAMESHIFT SUPPRESSION IN AMINOACYL-tRNA LIMITED CELLS
Authors: Weiss Robert B , Gallant Jonathan A 
Published: January 2021

ABSTRACT
Under certain conditions aminoacyl-tRNA limitation can phenotypically suppress frameshift alleles. The observed suppression is due to an increase in abnormal translocation of ribosomes translating codons that have a short supply of aminoacyl-tRNA. The rIIB frameshift alleles of bacteriophage T4 are used here to pinpoint the sites of ribosome frameshifting caused by these hypothetical decoding errors. The data indicate that not all hungry codons are associated with abnormal translocation, only a relatively small subset. Analysis of the hungry codons which are associated with ribosome frameshifting points to the existence of severe context effects determining the shiftiness of these codons.
THE MOLECULAR THROUGH ECOLOGICAL GENETICS OF ABNORMAL ABDOMEN. III. TISSUE-SPECIFIC DIFFERENTIAL REPLICATION OF RIBOSOMAL GENES MODULATES THE ABNORMAL ABDOMEN PHENOTYPE IN DROSOPHILA MERCATORUM
Authors: DeSalle Rob , Templeton Alan R 
Published: January 2021

ABSTRACT
The abnormal abdomen (aa) syndrome in Drosophila mercatorum is controlled by two major X-linked genetic elements. We have previously shown that the major X-linked element of aa is associated with the presence of large inserts in the 28S gene of the ribosomal RNA (rDNA) genes. We show that, in polytene tissue of wild-type D. mercatorum, the uninterrupted rDNA repeats are overreplicated relative to interrupted repeats. Uninterrupted rDNA repeats are also overreplicated in polytene tissue of hybrid larval offspring from wild-type and aa parents. This overreplication of uninterrupted repeats is not observed in diploid tissues of wild-type hybrids (of wild-type and aa parents) and homozygous aa larvae or in polytene tissue of aa larvae. Furthermore, molecular analysis of an aa line that has reverted to the wild type indicates that the reversion phenomenon is associated with the ability to overreplicate uninterrupted rDNA repeats in polytene tissues. The patterns of differential replication of rDNA genes in wild-type hybrids and aa larvae of D. mercatorum offer a possible mechanism for the tissue-specific control of the aa phenotype and suggest that the molecular basis for the second X-linked genetic element of aa is involved in the control of differential replication in polytene tissues.
A NUMERICAL SIMULATION OF THE ONE-LOCUS, MULTIPLE-ALLELE FERTILITY MODEL
Authors: Clark Andrew G , Feldman Marcus W 
Published: January 2021

ABSTRACT
Numerical simulations were performed to determine the equilibrium behavior of the one-locus fertility model in which fitness is considered as a property of a pair of mating diploids. A series of patterns of "fertility matrices" were considered for a single locus with two to six alleles. From these simulations, 19 different statistics were collected that characterize, at equilibrium, the heterozygosity, the mean fitness and the fate of populations begun at the allele-frequency centroid. For more than one-half of the trajectories produced by random fertility matrices, there was a decrease in the mean fitness at some time on the way to equilibrium. The mean number of alleles maintained at equilibrium increased only slightly with matrix dimension. Despite the potential for fertility models to display multiple stable equilibria, random fertility models maintain fewer distinct stable points than do random one-locus viability models. Pleiotropic models were also considered with fertility and viability selection operating sequentially within each generation. Most of the equilibrium statistics (with the exception of mean fertility) for the pleiotropic model were intermediate between the corresponding random viability and fertility models.
SEQUENCING STUDIES OF ICR-170 MUTAGENIC SPECIFICITY IN THE am (NADP-SPECIFIC GLUTAMATE DEHYDROGENASE) GENE OF NEUROSPORA CRASSA
Authors: Burns Philip A , Kinnaird Jane H , Kilbey Brian J , Fincham John R S 
Published: January 2021

ABSTRACT
The acridine half-mustard ICR-170-induced reversion of the mutant am15, which has a single base-pair deletion, at a frequency of between 9 and 28 × 10-6. In each of three classes of revertants, the mutagen had induced the insertion of a (see PDF) base pair at a (see PDF) site. The mutant am6, which has a single base pair insertion, is known to be revertible, with UV light, by deletion of a (see PDF) base pair at a (see PDF) site. This mutant reverted with ICR-170 at a frequency of 0.1 × 10-6. These results show that ICR-170 is able to induce addition frameshifts in Neurospora crassa within short, monotonous runs of G:C base pairs, but indicate a lack of deletion activity at such sequences.
RECOVERY AND CHARACTERIZATION OF TEMPERATURE-SENSITIVE MUTATIONS AFFECTING ADULT VIABILITY IN DROSOPHILA MELANOGASTER
Authors: Homyk Theodore , Sinclair Donald A R , Wong David T L , Grigliatti Thomas A 
Published: January 2021

ABSTRACT
Temperature-sensitive (ts) autonomous cell-lethal mutations have been used extensively to study important developmental phenomena, such as pattern formation, in Drosophila. Their utility would be enhanced considerably if it were possible to establish which cell type is primarily affected by each lesion. To facilitate such an approach we have isolated and characterized 21 EMS- induced X-linked adult-lethal (adl) mutants, 16 of which are ts. Most of these lesions also elicit ts lethal effects during preimaginal development. They represent 19 different loci distributed randomly along the X chromosome. The general properties of these mutations are described. In addition, results of an in-depth analysis (focus mapping and, in some cases, temperature shift and heat-pulse studies) of four strains, adl-1ts 1, sesE, adl-2ts 1 and rex are reported. Two major temperature-sensitive periods (TSPs) of adl-1 lethality were resolved: one during the second half of embryogenesis and the other coinciding with pupariation. Mosaic analysis revealed separate mesodermal foci for leg paralysis. Developmental analysis of adl-1 embryos suggest that the adl-1 product may be required for maintenance of muscle tissue. Two discrete TSPs of sesE lethality exist: one during the second instar and the other extending from late third instar to early pupation. Mosaic analysis of sesE lethality resolved a pair of neural foci, each of which appears to incorporate three separate foci for leg paralysis. Mosaic analysis of adl-2ts 1 revealed the existence of paired lethal foci that appear to map to the vicinity of the subesophageal ganglion. Analysis of rex mosaics resolved separate mesodermal foci for leg paralysis.
SOUTHERN ANALYSIS OF GENOMIC ALTERATIONS IN GAMMA-RAY-INDUCED APRT- HAMSTER CELL MUTANTS
Authors: Grosovsky Andrew J , Drobetsky Elliot A , deJong Pieter J , Glickman Barry W 
Published: January 2021

ABSTRACT
The role of genomic alterations in mutagenesis induced by ionizing radiation has been the subject of considerable speculation. By Southern blotting analysis we show here that 9 of 55 (approximately 1/6) gamma-ray-induced mutants at the adenine phosphoribosyl transferase (aprt) locus of Chinese hamster ovary (CHO) cells have a detectable genomic rearrangement. These fall into two classes: intragenic deletions and chromosomal rearrangements. In contrast, no major genomic alterations were detected among 67 spontaneous mutants, although two restriction site loss events were observed. Three gamma-ray-induced mutants were found to be intragenic deletions; all may have identical break-points. The remaining six gamma-ray-induced mutants demonstrating a genomic alteration appear to be the result of chromosomal rearrangements, possibly translocation or inversion events. None of the remaining gamma-ray-induced mutants showed any observable alteration in blotting pattern indicating a substantial role for point mutation in gamma-ray-induced mutagenesis at the aprt locus.
IN VIVO FUNCTION OF RARE G6pd VARIANTS FROM NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER
Authors: Eanes Walter F , Hey Jody 
Published: January 2021

ABSTRACT
From 1981 to 1983, 15,097 X-chromosomes were genetically extracted from a number of North American populations of D. melanogaster and were electrophoretically screened for rare mobility and activity variants of glucose-6-phosphate dehydrogenase (G6PD). Overall, 13 rare variants were recovered for a frequency of about 10-3. Eleven variants affect electrophoretic mobility and are apparently structural, and two variants exhibit low G6PD activity. One low activity variant is closely associated with a P-element insertion at 18D12-13—all of the variants were subjected to the previously described genetic scheme used to identify relative in vivo activity differences between the two common electrophoretic variants associated with the global polymorphism. Most of the rare variants exhibit apparent in vivo activities that are similar to one or the other of the common variants, and these specific rare variants appear to be geographically widespread. Several variants have significantly reduced function. All of the variants were measured for larval specific activity for G6PD as a first measure of in vitro activity. It appears that specific activity alone is not a sufficient predictor for G6PD in vivo function.
X-LINKED FEMALE-STERILE LOCI IN DROSOPHILA MELANOGASTER
Authors: Perrimon Norbert , Mohler Dawson , Engstrom Lee , Mahowald A P 
Published: January 2021

ABSTRACT
We have examined the number of X-linked loci specifically required only during oogenesis. Complementation analyses among female-sterile (fs) mutations obtained in two mutagenesis screens—Gans' and Mohler's—indicate that any fs locus represented by two or more mutant alleles in Gans' collection are usually present in Mohler's collection. However, when a locus is represented by a single allele in one collection, it is generally not present in the other collection. We propose that this discrepancy is due to the fact that most "fs loci" represented by less than two mutant alleles are, in fact, vital (zygotic lethal) genes, and that the fs alleles are hypomorphic mutations of such genes. In support of this hypothesis we have identified lethal alleles at 12 of these "fs loci." The present analysis has possibly identified all maternal-effect lethal loci detectable by mutations on the X chromosome and has allowed us to reevaluate the number of "ovary-specific fs" loci in the Drosophila genome. Finally, germline clone analysis of a large number of fs mutations was performed in order to estimate the relative contribution of germline and somatic cell derivatives to oogenesis and to embryonic development. All the maternal-effect lethal loci tested are germline-dependent.
GENETICS OF GLUCOCORTICOID RECEPTOR LEVELS IN RECOMBINANT INBRED LINES OF MICE
Authors: Liu Sharon L , Erickson Robert P 
Published: January 2021

ABSTRACT
Hepatic glucocorticoid receptor binding activity was measured in A/J, C57BL/6J, their F1 reciprocal crosses and their F1 recombinant inbred (RI) lines. The glucocorticoid binding capacity was measured in Hepes buffer and Hepes buffer plus dithiothreitol (DTT). The A/J parental strain showed higher levels, and a greater increase of glucocorticoid binding in the presence of DTT, than did the C57BL/6J strain. The response of binding in the presence of DTT to that without DTT was expressed as a ratio. The levels and distribution of these measurements among the RI lines and F1 reciprocal crosses suggested that there was a maternal effect on glucocorticoid receptor binding capacity. The data on RI lines suggested epistatic interactions, but could fit a two-gene model. β2-Microglobulin, β-glucuronidase and H-2 (located on chromosomes 2, 5, and 17, respectively) were chosen to analyze any association to glucocorticoid receptor binding, because they have been considered to be related to glucocorticoid-induced cleft palate or glucocorticoid receptors. No significant associations were found.
THE QUESTION OF THE TOTAL GENE NUMBER IN DROSOPHILA MELANOGASTER
Authors: Lefevre George , Watkins William 
Published: January 2021

ABSTRACT
A statistical analysis has been carried out on the distribution and allelism of nearly 500 sex-linked, X-ray-induced, cytologically normal and rearranged lethal mutations in Drosophila melanogaster that were obtained by G. Lefevre. The mutations were induced in four different regions of the X chromosome: (1) 1A1-3E8, (2) 6D1-8A5, (3) 9E1-11A7 and (4) 19A1-20F4, which together comprise more than one-third of the entire chromosome.—The analysis shows that the number of alleles found at different loci does not fit a Poisson distribution, even when the proper procedures are taken to accomodate the truncated nature of the data. However, the allele distribution fits a truncated negative binomial distribution quite well, with cytologically normal mutations fitting better than rearrangement mutations. This indicates that genes are not equimutable, as required for the data to fit a Poisson distribution.—Using the negative binomial parameters to estimate the number of genes that did not produce a detectable lethal mutation in our experiment (n0) gave a larger number than that derived from the use of the Poisson parameter. Unfortunately, we cannot estimate the total numbers of nonvital loci, loci with undetectable phenotypes and loci having extremely low mutabilities. In any event, our estimate of the total vital gene number was far short of the total number of bands in the analyzed regions; yet, in several short intervals, we have found more vital genes than bands; in other intervals, fewer. We conclude that the one-band, one-gene hypothesis, in its literal sense, is not true; furthermore, it is difficult to support, even approximately.—The question of the total gene number in Drosophila will, not doubt, eventually be solved by molecular analyses, not by statistical analysis of mutation data or saturation studies.
TEMPORAL VARIATION FOR THE EXPRESSION OF CATALASE IN DROSOPHILA MELANOGASTER: CORRELATIONS BETWEEN RATES OF ENZYME SYNTHESIS AND LEVELS OF TRANSLATABLE CATALASE-MESSENGER RNA
Authors: Bewley Glenn C , Mackay William J , Cook Julia L 
Published: January 2021

ABSTRACT
Two variants that alter the temporal expression of catalase have been isolated from a set of third chromosome substitution lines. Each variant has been mapped to a cytogenetic interval flanked by the visible markers st (3-44.0) and cu (3-50.0) at a map position of 47.0, which is within or near the interval 75D-76A previously identified as containing the catalase structural gene on the bases of dosage responses to segmental aneuploidy. Each variant operates by modulating the rate of enzyme synthesis and the level of translatable catalase-mRNA.
OM MUTATIONS IN DROSOPHILA ANANASSAE ARE LINKED TO INSERTIONS OF A TRANSPOSABLE ELEMENT
Authors: Shrimpton Antony E , Montgomery Elizabeth A , Langley Charles H 
Published: January 2021

ABSTRACT
It has been hypothesized that Om mutability in Drosophila ananassae (involving spontaneous mutation at 20 loci, resulting in semidominant, nonpleiotropic eye morphology defects) was due to insertion of a transposable element, tom. One particularly unstable Χ-linked Om allele produced several derivatives, one of which has a more extreme Om phenotype and was accompanied by a singed bristle mutant, sn9g. DNA probes from the sn locus of D. melanogaster were used to clone the homologous region of D. ananassae. Analysis of sn9g DNA detected a 6.5-kb insert. Genomic Southern blotting and in situ hybridization techniques showed that this insert is repetitive and dispersed. The existence of the tom element is supported by genetic mapping that established homology between the 6.5-kb sn9g insert and Om mutants at the four Χ-linked loci tested.