bluuebunny/crossref_metadata_2025_split huggingface dataset:
VIABILITY INTERACTIONS, IN VIVO ACTIVITY AND THE G6PD POLYMORPHISM IN DROSOPHILA MELANOGASTER
Authors: Eanes Walter F 
Published: January 2021

ABSTRACT
Several biochemical studies have suggested that in Drosophila melanogaster the two common allozymes of G6PD differ in their in vitro activities and thermal stabilities. Yet, it remains to be shown that these characterizations reflect actual in vivo differences and are not artifacts of the biochemical approach. In this study it is shown that in vivo activity differences must exist between these two variants. This conclusion arises from the observation that the viability of flies bearing a low activity allele of 6PGD is strongly dependent on the genotype at the G6PD (Zw) locus, whereas no measurable difference in viability can be detected between Zw genotypes in a normal activity 6PGD background. These viability interactions are in the direction predicted by the reported in vitro activities of the allozymes and the proposed deleterious effects of 6-phosphogluconate accumulation.—In addition, a genetic scheme is used that uncouples and quantifies the effects of viability modifiers in the region of the Zw locus, while homogenizing 98% of the X chromosome. The viability of different Zw genotypes is measured by examining whole chromosome viabilities relative to the FM6 balancer chromosome. The advantages of this particular scheme are discussed.
THE ROLE OF PYRIMIDINE DIMERS AS PREMUTAGENIC LESIONS: A STUDY OF TARGETED VS. UNTARGETED MUTAGENESIS IN THE lacI GENE OF ESCHERICHIA COLI
Authors: Kunz Bernard A , Glickman Barry W 
Published: January 2021

ABSTRACT
We have employed conjugal transfer of an F′ lac episome to examine targeted and untargeted mutagenesis in the lacI gene of Escherichia coli and to determine the relative importance of pyrimidine dimers as premutational UV lesions compared to (6-4) photoproducts that also may have a mutational role. This conjugal system allowed us to assess the premutagenic role of UV lesions independently from any role as inducers of SOS functions. F′ DNA was transferred to an SOS-induced recipient strain from: unirradiated donor cells, UV-treated donor cells or donor cells that were irradiated and then exposed to photoreactivating light. The results indicate that SOS-related, untargeted events may account for as much as one-third of the nonsense mutations (i.e., base substitutions) recovered after undamaged F′ DNA is transferred to UV-irradiated recipients. When the donor strain also is irradiated, in excess of 90% of the mutations detected following conjugation appear to be targeted. Photoreactivation of the UV-treated donor cells, prior to F′ transfer to the SOS-induced recipient strain, demonstrated that in this experimental system virtually all recovered UV-induced mutations are targeted by photoreactivable lesions. We presume that these lesions are pyrimidine dimers because (6-4) photoproducts are not photoreactivable.
SEX CHROMOSOME MEIOTIC DRIVE IN DROSOPHILA MELANOGASTER MALES
Authors: McKee Bruce 
Published: January 2021

ABSTRACT
In Drosophila melanogaster males, deficiency for X heterochromatin causes high X-Y nondisjunction and skewed sex chromosome segregation ratios (meiotic drive). Y and XY classes are recovered poorly because of sperm dysfunction. In this study it was found that X heterochromatic deficiencies disrupt recovery not only of the Y chromosome but also of the X and autosomes, that both heterochromatic and euchromatic regions of chromosomes are affected and that the "sensitivity" of a chromosome to meiotic drive is a function of its length. Two models to explain these results are considered. One is a competitive model that proposes that all chromosomes must compete for a scarce chromosome-binding material in Xh - males. The failure to observe competitive interactions among chromosome recovery probabilities rules out this model. The second is a pairing model which holds that normal spermiogenesis requires X-Y pairing at special heterochromatic pairing sites. Unsaturated pairing sites become gametic lethals. This model fails to account for autosomal sensitivity to meiotic drive. It is also contradicted by evidence that saturation of Y-pairing sites fails to suppress meiotic drive in Xh - males and that extra X-pairing sites in an otherwise normal male do not induce drive. It is argued that meiotic drive results from separation of X euchromatin from X heterochromatin.
MORPHOGENETICALLY SPECIFIC MUTABILITY IN DROSOPHILA ANANASSAE
Authors: Hinton Claude W 
Published: January 2021

ABSTRACT
A stock exhibiting hypermutability with respect to visible mutants (Om) affecting optic morphology was subjected to genetic analysis. The production of Om mutants, independently recovered with a frequency of two per 104, is restricted to females and depends primarily on homozygosity of their X chromosomes; in heterozygotes, Ommutability is stimulated by the presence of either one of two extrachromosomally replicating elements previously identified in other stocks having cryptic mutability systems. The semidominant and nonpleiotropic Om mutants are not associated with gross rearrangements and they map to at least 15 loci. Most of the loci defined by mapping are represented by two or more Ommutants which, despite considerable interlocus mimicry, sometimes display locus-specific phenotypes. Om mutants are moderately unstable, and they are subject to dominant suppressors that arise spontaneously at either of two X-linked loci. An interpretation of these observations invokes an X-linked transposable element (tom) that specifically inserts into control sequences shared by a set of structural genes involved in eye morphogenesis.
PLOIDY BARRIER TO ENDOSPERM DEVELOPMENT IN MAIZE
Authors: Lin Bor-Yaw 
Published: January 2021

ABSTRACT
Maize kernels inheriting the indeterminate gametophyte mutant (ig) on the female side had endosperms that ranged in ploidy level from diploid (2x) to nonaploid (9x). In crosses with diploid males, only kernels of the triploid endosperm class developed normally. Kernels of the tetraploid endosperm class were half-sized but with well-developed embryos that regularly germinated. Kernels of endosperm composition other than triploid or tetraploid were abortive.—Endosperm ploidy level resulting from mating ig/igx tetraploid Ig similarly was variable. Most endosperms started to degenerate soon after pollination and remained in an arrested state. Hexaploid endosperm was exceptional; it developed normally during the sequence of stages studied and accounted for plump kernels on mature ears. Since such kernels have diploid maternal tissues (pericarp) but triploid embryos, the present finding favors the view that endosperm failure or success in such circumstances is governed by conditions within the endosperm itself.—Whereas tetraploid endosperm consisting of three maternal genomes and one paternal genome is slightly reduced in size but supports viable seed development, that endosperm having two maternal and two paternal chromosome sets was highly defective and conditioned abortion. Thus, development of maize endosperm evidently is affected by the parental source of its sets of chromosomes.
COPY NUMBER CONTROL OF Tn5 TRANSPOSITION
Authors: Johnson Reid C , Reznikoff William S 
Published: January 2021

ABSTRACT
Transposition of Tn5 in Escherichia coli strains containing one or multiple copies of the transposable element was investigated. It was found that the overall frequency of transposition within a cell remained constant regardless of the number of copies of Tn5 present in that cell. Experiments measuring the transposition frequency of differentially marked Tn5s confirmed that the frequency of transposition of an individual Tn5 decreased proportionally with the total number of copies of the element present in a cell. The IS50R-encoded function, protein 2, which has previously been shown to be an inhibitor of transposition, is sufficient to mediate this inhibitory effect. The concentration of protein 2 in a cell appears to modulate the transposition of individual Tn5 elements in such a way that the overall transposition of Tn5 in a cell remains constant.
FREQUENT IMPRECISE EXCISION AMONG REVERSIONS OF A P ELEMENT-CAUSED LETHAL MUTATION IN DROSOPHILA
Authors: Voelker Robert A , Greenleaf Arno L , Gyurkovics Henrik , Wisely G Bruce , Huang Shu-Mei , Searles Lillie L 
Published: January 2021

ABSTRACT
RpII215D 50 (= D50) is a lethal mutation caused by the insertion of a 1.3-kb P element 5′ to sequences encoding the largest (215 kilodaltons) subunit of Drosophila RNA polymerase II. In dysgenic males D50 reverted to nonlethality at frequencies ranging from 2.6 to 6.5%. These reversions resulted from loss of P element sequences. Genetic tests of function and restriction enzyme analysis of revertant DNAs revealed that 35% or more of the reversion events were imprecise excisions. Two meiotic mutations that perturb excision repair and postreplication repair (mei-9a and mei-41D 5, respectively) had no influence on reversion frequency but may have increased the proportion of imprecise excisions. We suggest that these excisions are by-products of, rather than intermediates in, the transposition process.
FACTORS INFLUENCING DISPROPORTIONATE REPLICATION OF THE RIBOSOMAL RNA CISTRONS IN DROSOPHILA MELANOGASTER
Authors: Dutton F Lee , Krider Hallie M 
Published: January 2021

ABSTRACT
This report describes studies of the compensatory response employing D. melanogaster stocks that bear cloned-X chromosomes derived from laboratory populations of strains Oregon R and Canton S. We find that modification of the autosomal background in either the female or the (see PDF) male parent influences the expression of the compensatory response by X chromosomes derived from the Canton S population, whereas Oregon R isolates are unresponsive to these effects. We have also studied compensatory replication in X/O larvae produced from cloned-X derivatives of both Canton S and Oregon R. Canton S larval compensation exceeds that of the adult, whereas in Oregon R the converse is true. We have concluded that both X chromosomal and autosomal factors affect the expression and magnitude of the compensatory response.
RIBOSOMAL RNA CISTRONS OF X CHROMOSOMES CLONALLY DERIVED FROM D. MELANOGASTER LABORATORY POPULATIONS: REDUNDANCY, ORGANIZATION AND STABILITY
Authors: Dutton F Lee , Krider Hallie M 
Published: January 2021

ABSTRACT
To determine whether heterogeneity exists in the organization or redundancy of the rRNA cistrons of inbred populations of Drosophila melanogaster, we have derived a number of sublines from the strains Oregon R and Canton S. These two strains were chosen because our previous studies have demonstrated a difference in the competence of these strains to exhibit a "compensatory response" of the rDNA. In each subline, the X chromosomes are descended from a single maternal X, that is, each line is homozygous for a particular nucleolus organizer (NO). These derivative lines have been characterized in terms of rDNA content and organization, using quantitative liquid hybridizations and Southern blot analyses, respectively. Our studies reveal that both of the highly inbred parent populations contained a heterogeneous array of X chromosomal rDNA contents. Once isogenized, the rDNA redundancy of a given X chromosomal NO can be shown to remain stable for at least 20 generations in culture. We detect no restriction pattern heterogeneity among X chromosomes isolated from a given strain, despite relatively large differences in their rDNA contents. This leads us to suggest that there is no significant clustering of intervening sequence-bearing (ivs +) genes within the rDNA loci of chromosomes from the populations examined. Furthermore, we conclude that apparent alterations in rDNA redundancy known as the compensatory response are not related to the heterogeneity of rDNA content within a population.
THERMAL RESCUE OF UV-IRRADIATED BACTERIOPHAGE T4 AND BIPHASIC MODE OF ACTION OF THE WXY SYSTEM
Authors: Conkling Mark A , Drake John W 
Published: January 2021

ABSTRACT
When ultraviolet-irradiated bacteriophage T4 is assayed at plating temperatures ranging from 20° to 40°, its survival increases at the higher temperatures. This "thermal rescue" requires an intact WXY system but not the denV pyrimidine dimer excision system. Mutation rates decrease with increasing temperature, indicating that some lesions processed in a mutagenic manner at lower temperatures are accurately repaired or circumvented at high temperatures. When both the cold sensitivity of UV survival in the wild type and the temperature sensitivity of newly isolated ts mutants of uvsX and uvsY were used, expression of the WXY system was monitored in temperature shift UV survival experiments and was found to be biphasic: the uvsX and uvsY functions increase UV survival in two increments, one at an early and another at a late stage of infection. The uvsW function, however, increases UV survival only early in infection.
MUTATIONS AFFECTING FUNCTIONS OF THE DROSOPHILA GENE GLUED
Authors: Garen Alan , Miller Barbara R , Paco-Larson M Luisa 
Published: January 2021

ABSTRACT
Glued mutations in Drosophila comprise an essential complementation group with complex developmental effects. The original Glued mutation (Gl) has dominant nonlethal effects in heterozygous flies, principally on the morphogenesis of the visual system. Gl also has a recessive lethal effect early in development. Mutations that reverse the dominant visual effects of Gl (GlR mutations) were induced by γ-radiation or by insertions of the transposable P element. The GlR(G) mutations induced by γ-radiation do not reverse the lethal effect of Gl; these appear to be null mutations, some of which (and possibly all) delete segments of the Glued region. The GlR(P) mutations induced by insertion of the P element also reverse concomitantly a recessive lethal effect of Gl, suggesting that both the recessive and dominant effects are controlled by the same gene. The reversal of a lethal effect of Gl by the P element is remarkable, since it indicates that an essential gene function can be restored by insertion of unrelated DNA. Another class of lethal Glued mutations was induced in the normal Gl + strain by ethyl methanesulfonate (EMS). The EMS mutations belong to the same essential complementation group as Gl, but do not have the strong dominant effects of Gl on the visual system.—The GlR(P) mutations provide a molecular marker for the Glued gene, which was used to map the gene to the 70C2 band of chromosome 3L by in situ hybridization of a P element probe to polytene chromosomes from the GlR(P) strains and also to isolate clones of Glued genomic DNA for molecular studies of the normal gene and the various Glued mutations.
CROSSES BETWEEN INSERTION AND POINT MUTATIONS IN Λ GENE cI: STIMULATION OF NEIGHBORING RECOMBINATION BY HETEROLOGY
Authors: Lieb M , Tsai M M , Deonier Richard C 
Published: January 2021

ABSTRACT
Intragenic recombination between λcl point mutations and insertions was studied in four-factor crosses. In crosses between two point mutations, there is a linear relationship between recombination frequency and distance. However, in crosses between an insertion and point mutations, there is additional recombination in the regions 200 base pairs to the right and to the left of the insertion. The recombinational stimulation occurred with IS insertions and also with insertions consisting of HindIII fragments of SV40 and with a deletion that removes part of cI. This indicated that the stimulation was a result of heterology per se rather than of information encoded by the insertions. Either Rec or Red functions are sufficient for enhanced recombination near a heterology. The stimulation is attributed to more frequent resolution of recombinational intermediates in the neighborhood of a heterology. "Stalling" of migrating branches or invading strands at a heterology may increase the probability of local DNA cleavage.
GENETIC ANALYSIS OF CHROMOMERE 3D4 IN DROSOPHILA MELANOGASTER . II. REGULATORY SITES FOR THE DUNCE GENE
Authors: Salz Helen K , Kiger John A 
Published: January 2021

ABSTRACT
Chromomere 3D4 of the X chromosome of D. melanogaster contains two genes, dunce (dnc) and sperm amotile (sam). Mutations in dnc cause defects in memory formation and female fertility and reduce or eliminate the activity of a cAMP-specific phosphodiesterase designated form II. A fine structure map of this region has been constructed showing the locations of two sam mutations, five dnc mutations and a newly identified locus designated control of fertility (cf) that acts in cis to regulate the female sterility phenotype of dnc. The two sam mutations are separated by 0.02 ± 0.01 cM, the rightmost being located 0.08 ± 0.02 cM to the left of the null mutation dncm 11. A cluster of null and form II-defective dnc mutations is located 0.04 ± 0.01 cM to the right of dncm 11. The cf locus is 0.06 ± 0.02 cM to the right of this cluster. The location of the dnc and cf sites identify a region of approximately 0.10 cM that is required for proper expression of dnc +. The dncck mutation, associated with a reciprocal translocation between 3L and the X, exhibits reduced form II activity and female sterility. This translocation breakpoint has been mapped to the left of the dnc + gene and is near the breakpoint of Df(1)N 64j15 which also reduces expression of dnc +. The effect of these independent chromosomal breaks on the dnc + gene suggests the existence of a site to the left of dnc + that is also required for proper expression of the gene.
GENETIC ANALYSIS OF ISOZYME LOCI IN TETRAPLOID POTATOES (SOLANUM TUBEROSUM L.)
Authors: Martinez-Zapater J M , Oliver Jose L 
Published: January 2021

ABSTRACT
The genetic control of eight isozyme loci revealed by starch gel electrophoresis was studied through the analysis of three progenies derived from four tetraploid cultivars of Solanum tuberosum (groups Andigena and Tuberosum). Duplicate gene expression was found in seven (Got-A, Got-B, Pgd-C, Pgi-B, Pgm-A, Pgm-B and Pox-C) isozyme loci. In another isozyme gene (Adh-A), the parental genotypes were not adequate to distinguish between a monogenic or a digenic model of genetic control. Tetrasomic inheritance was demonstrated in four (Got-A, Got-B, Pgd-C and Pgi-B) isozyme loci. In the remaining duplicate genes, the parental genotypes precluded discrimination between disomic or tetrasomic models. Tetrasomic segregations of the chromosomal type were generally found; however, the isozyme phenotypes shown by three descendants from selfing cv. Katahdin indicate the occurrence of chromatid segregations, although aneuploidy cannot be ruled out. Either autoploidy or amphidiploidy with lack of chromosome differentiation between the two diploid ancestors can account for the existence of tetrasomic inheritance in the common potato.
DETECTION OF NONRANDOM ASSOCIATION OF ALLELES FROM THE DISTRIBUTION OF THE NUMBER OF HETEROZYGOUS LOCI IN A SAMPLE
Authors: Chakraborty Ranajit 
Published: January 2021

ABSTRACT
The distribution of the number of heterozygous loci in two randomly chosen gametes or in a random diploid zygote provides information regarding the nonrandom association of alleles among different genetic loci. Two alternative statistics may be employed for detection of nonrandom association of genes of different loci when observations are made on these distributions: observed variance of the number of heterozygous loci (s 2 k) and a goodness-of-fit criterion (X 2) to contrast the observed distribution with that expected under the hypothesis of random association of genes. It is shown, by simulation, that s 2 k is statistically more efficient than X 2 to detect a given extent of nonrandom association. Asymptotic normality of s 2 k is justified, and X 2 is shown to follow a chi-square (X2) distribution with partial loss of degrees of freedom arising because of estimation of parameters from the marginal gene frequency data. Whenever direct evaluations of linkage disequilibrium values are possible, tests based on maximum likelihood estimators of linkage disequilibria require a smaller sample size (number of zygotes or gametes) to detect a given level of nonrandom association in comparison with that required if such tests are conducted on the basis of s 2 k. Summarization of multilocus genotype (or haplotype) data, into the different number of heterozygous loci classes, thus, amounts to appreciable loss of information.
SPONTANEOUS UNSTABLE UNC-22 IV MUTATIONS IN C. ELEGANS VAR. BERGERAC
Authors: Moerman D G , Waterston R H 
Published: January 2021

ABSTRACT
This paper describes a mutator system in the nematode Caenorhabditis elegans var. Bergerac for the gene unc-22. Of nine C. elegans and two C. briggsae strains tested only the Bergerac BO strain yielded mutant animals at a high frequency and the unc-22 IV gene is a preferred mutational target. The forward spontaneous mutation frequency at the unc-22 locus in Bergerac BO is about 1 × 10-4, and most of these spontaneous unc-22 mutations revert at frequencies between 2 × 10-3 and 2 × 10-4. Both the forward mutation frequency and the reversion frequency are sensitive to genetic background. Spontaneous unc-22 mutations derived in a Bergerac background and placed in a primarily Bristol background revert at frequencies of &lt;10-6. When reintroduced into a Bergerac/Bristol hybrid background the mutations once again become unstable.
The mutator activity could not be localized to a discrete site in the Bergerac genome. Nor did mutator activity require the Bergerac unc-22 gene as a target since the Bristol unc-22 homolog placed in a Bergerac background also showed high mutation frequency. Intragenic mapping of two spontaneous unc-22 alleles, st136 and st137, place both mutations in the central region of the known unc-22 map. However, these mutations probably recombine with one another, suggesting that the unstable mutations can occur in more than one site in unc-22. Examination of the phenotypic effect of these mutations on muscle structure indicates that they are less severe in their effect than a known amber allele. We suggest that this mutator system is polygenic and dispersed over the nematode genome and could represent activity of the transposable element Tc1.