bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ds-INDUCED ALLELES AT THE OPAQUE-2 LOCUS OF MAIZE
Authors: Motto Mario , Marotta Renzo , Di Fonzo Natale , Soave Carlo , Salamini Francesco 
Published: January 2021

ABSTRACT
Transposon mutagenesis has been used to isolate mutable alleles at the Opaque-2 (O2) locus of maize. Plants with the Activator-Dissociation (Ac-Ds) system of transposable elements and O2 were crossed as males to a stable o2 tester line. Among a population of 200,000 kernels, 198 exceptional kernels with somatic instability were recovered. In four cases, designated O2-m1, o2-m2, O2-m3 and O2-m4, variegated phenotypes appeared in F2 and subsequent generations. Genetic analyses indicated that the presence of Ds near or within the O2 gene was responsible for the observed somatic instability at the O2 locus. The phenotypes of the newly induced alleles were of two types. Alleles O2-m1, O2-m3 and O2-m4, in the absence of Ac, were characterized by kernel phenotypes indistinguishable from the wild type; in the presence of Ac they generated kernels with opaque sectors interspersed within a vitreous background. In contrast, the mutable allele o2-m2, in the absence of Ac, was characterized by kernels with a recessive phenotype similar to o2 recessive mutants. In the presence of Ac, it reverted somatically to wild-type-producing kernels with vitreous spots in an o2 background. The association of the Ds element with the O2 locus may prove a valuable tool directed to the isolation of DNA fragments bearing the O2 gene.
MULTILOCUS POPULATION GENETICS WITH WEAK EPISTASIS. II. EQUILIBRIUM PROPERTIES OF MULTILOCUS MODELS: WHAT IS THE UNIT OF SELECTION?
Authors: Hastings Alan 
Published: January 2021

ABSTRACT
Using perturbation techniques, I study the equilibrium of deterministic discrete time multilocus models with weak epistasis. The most important results are on the relationship between epistasis and disequilibrium. Disequilibrium involving a particular set of loci reflects only epistasis simultaneously involving those loci. Moreover, all the disequilibria of all orders vary approximately as the inverse of the probability of at least one recombination event among the loci involved. Finally, higher order disequilibria among loci will be lower than lower order ones, even if the level of epistasis is the same at all orders. In this sense, the unit of selection is small. However, given the larger number of higher order disequilibria, these higher order disequilibria may play an important role in the computation of gametic frequencies from allelic frequencies in models with a large number of loci. Finally, I show that epistasis between blocks of loci will be averages of epistatic effects, not additions of epistatic effects. Thus, failure to find significant epistasis on a chromosomal basis does not rule out the importance of epistatic effects.
MOST UV-INDUCED RECIPROCAL TRANSLOCATIONS IN SORDARIA MACROSPORA OCCUR IN OR NEAR CENTROMERE REGIONS
Authors: Leblon G , Zickler D , Lebilcot S 
Published: January 2021

ABSTRACT
In fungi, translocations can be identified and classified by the patterns of ascospore abortion in asci from crosses of rearrangement x normal sequence. Previous studies of UV-induced rearrangements in Sordaria macrospora revealed that a major class (called type III) appeared to be reciprocal translocations that were anomalous in producing an unexpected class of asci with four aborted ascospores in bbbbaaaa linear sequence (b = black; a = abortive). The present study shows that the anomalous type III rearrangements are, in fact, reciprocal translocations having both breakpoints within or adjacent to centromeres and that bbbbaaaa asci result from 3:1 disjunction from the translocation quadrivalent.—Electron microscopic observations of synaptonemal complexes enable centromeres to be visualized. Lengths of synaptonemal complexes lateral elements in translocation quadrivalents accurately reflect chromosome arm lengths, enabling breakpoints to be located reliably in centromere regions. All genetic data are consistent with the behavior expected of translocations with breakpoints at centromeres.—Two-thirds of the UV-induced reciprocal translocations are of this type. Certain centromere regions are involved preferentially. Among 73 type-III translocations, there were but 13 of the 21 possible chromosome combinations and 20 of the 42 possible combinations of chromosome arms.
CYTOGENETIC ANALYSIS OF THE cSOD MICROREGION IN DROSOPHILA MELANOGASTER
Authors: Campbell Shelagh D , Hilliker Arthur J , Phillips John P 
Published: January 2021

ABSTRACT
This report describes the genetic organization of a euchromatic region on the third chromosome of Drosophila melanogaster extending cytologically from 68A2 to C1, an interval comprising 10 or 11 polytene chromosome bands. The gene for cytoplasmic superoxide dismutase (cSOD) maps within this interval, as does low xanthine dehydrogenase (lxd).—Recessive lethal mutations were generated within the region by ethyl methanesulfonate mutagenesis and by hybrid dysgenesis. These lethals fall into 11 functional groups, which were partially ordered by complementation with deletions having breakpoints within the region. The distribution of dysgenesis-induced mutations in the region is highly nonrandom, the majority being within a single group. The mutability of this gene is comparable to that of singed (sn), a documented "hot-spot" for P-element insertion.—One of the EMS-induced lethals, l-108, fulfills biochemical criteria expected of a hypomorphic allele of cSOD. To our knowledge this is the first such allele recovered of this gene, and it should prove very useful in an analysis of the in vivo function of cytoplasmic SOD. Indeed, it has been demonstrated that cSOD is almost certainly a vital gene.
MOLECULAR MAPPING OF THE ROSY LOCUS IN DROSOPHILA MELANOGASTER
Authors: Coté Babette , Bender Welcome , Curtis Daniel , Chovnick Arthur 
Published: January 2021

ABSTRACT
The DNA from the chromosomal region of the Drosophila rosy locus has been examined in 83 rosy mutant strains. Several spontaneous and radiation-induced alleles were associated with insertions and deletions, respectively. The lesions are clustered in a 4-kb region. Some of the alleles identified on the DNA map have been located on the genetic map by fine-structure recombination experiments. The genetic and molecular maps are collinear, and the alignment identifies the DNA location of the rosy control region. A rosy RNA of 4.5 kb has been identified; its 5' end lies in or near the control region.
POPULATION GENETICS OF AN EXPANDING FAMILY OF MOBILE GENETIC ELEMENTS
Authors: Ohta Tomoko 
Published: January 2021

ABSTRACT
A model of an expanding family of dispersed repetitive DNA was studied. Based on the previous result of the model of duplicative transposition, an approximate solution to give allelism and identity coefficients as functions of time was obtained, and theoretical predictions were verified by Monte Carlo experiments. The results show that, even if the copy number per genome increases very rapidly, allelism and identity coefficients may take a long time to reach equilibrium. The changes of allelism and allelic identity are similar to that of homozygosity at an ordinary single locus, whereas that of nonallelic identity can be much slower, particularly when the copy number per genome is large. Thus, many existing families of highly repetitive sequences may represent nonequilibrium states for nonallelic identity. The present model may be extended to include other evolutionary forces such as gene conversion or the recurrent insertion from normal gene copies.
A GLYOXALASE-1 VARIANT ASSOCIATED WITH THE t-COMPLEX IN HOUSE MICE
Authors: Nadeau Joseph H 
Published: January 2021

ABSTRACT
A quantitative variant of glyoxalase-1 associated with the t-complex in house mice is described. GLO-1C in red cell lysates from mice heterozygous for complementing t-haplotypes and from mice homozygous for the tw 8-haplotype had less than one-third the GLO-1 activity of NZB/BINJ, the inbred strain with the lowest activity previously reported. GLO-1C appeared to be determined by the structural locus Glo-1 and, together with two partial t 6-haplotypes, was used to map Glo-1 to the telomeric portion of the t 6-haplotype. Glo-1c was associated with all t-haplotypes tested and has not been found in mice that lack a t-complex. Thus, this variant of Glo-1c provides both a further example of gametic disequilibrium between the t-complex and linked loci and a readily identifiable marker for the t-complex.
ISOLATION AND CHARACTERIZATION OF A MOUSE Y CHROMOSOMAL REPETITIVE SEQUENCE
Authors: Nishioka Yutaka , Lamothe Estelle 
Published: January 2021

ABSTRACT
The Y chromosome plays a dominant role in mammalian sex determination, and characterization of this chromosome is essential to understand the mechanism responsible for testicular differentiation. Male mouse genomic DNA fragments, cloned into pBR322, were screened for the presence of Bkm (a female snake satellite DNA)-related sequences, and we obtained a clone (AC11) having a DNA fragment from the mouse Y chromosome. In addition to a Bkm-related sequence, this fragment contained a Y chromosomal repetitive sequence. DNA isolated from the XX sex-reversed male genome produced a hybridization pattern indistinguishable to that obtained with normal female DNA, suggesting that the AC11 sequence is not contained within the Y chromosomal DNA present in the sex-reversed male genome. Based on the hybridization patterns against mouse Y chromosomal DNA, AC11 classified 16 inbred laboratory strains into two categories; those with the Mus musculus musculus type Y chromosome and those with the M.m. domesticus type Y chromosome. Three European subspecies of Mus musculus (M.m. brevirostris, M.m. poschiavinus and M.m. praetextus) possessed the M.m. domesticus type Y chromosome, whereas the Japanese mouse, M.m. molossinus, had the M.m. musculus type Y chromosome. The survey was also extended to six other species that belong to the genus Mus, of which M. spretus and M. hortulanus showed significant amounts of AC11-related sequences in their Y chromosomes. The male-specific accumulation of AC11-related sequences was not found in M. caroli, M. cookii, M. pahari or M. platythrix. This marked difference among Mus species indicates that the amplification of AC11-related sequences in the mouse Y chromosome was a recent evolutionary event.
GENETICAL AND MOLECULAR ANALYSES OF qa-2 TRANSFORMANTS IN NEUROSPORA CRASSA
Authors: Case Mary E 
Published: January 2021

ABSTRACT
Neurospora crassa qa-2 + transformants from five different donor DNA clones were analyzed by genetical and molecular techniques. None of the 32 transformants have the qa-2 + DNA replacing the qa-2 - gene in linkage group VII. In one transformant, the qa-2 + DNA was inserted adjacent to the qa-2 - gene. Thirty-one transformants have the qa-2 + inserts at sites not linked, or not closely linked, to the qa-2 locus in LG VII. Plasmid sequences were integrated along with the qa-2 + gene in 28 transformants. In the unlinked duplication-type transformants, catabolic dehydroquinase (the qa-2 + gene product) was induced at 5—100% of the wild-type-induced enzyme activity, with 24 transformants in the 5—80% range. The reduced levels of enzyme activity may be due to "position effects" of sequences adjacent to the integration site either in the N. crassa genomic DNA or in the flanking plasmid (pBR322 or pBR325) sequences. Unexpected gene conversion-like events, in which a qa-2 + gene was changed to qa-2 -, were observed in tetrads from intercrosses between unlinked duplication-type transformants and in selfings of such transformants.
BIPARENTAL INHERITANCE OF NON-MENDELIAN GENE MARKERS IN CHLAMYDOMONAS MOEWUSII
Authors: Lee Robert W , Lemieux Claude 
Published: January 2021

ABSTRACT
The first two non-Mendelian gene mutations to be identified in Chlamydomonas moewusii are described. These putative chloroplast gene mutations include one for resistance to streptomycin (sr-nM1) and one for resistance to erythromycin (er-nM1). In one- and two-factor reciprocal crosses, usually over 90% of the germinating zygospores transmitted these mutations and their wild-type alternatives from both parents (biparental zygospores); the remaining zygospores transmitted exclusively the non-Mendelian markers of the mating-type "plus" parent. Among the biparental zygospores, a strong bias in the transmission of non-Mendelian alleles from the mating-type "plus" parent was indicated by an excess of meiotic and postmeiotic mitotic progeny that were homoplasmic for non-Mendelian alleles from this parent compared to those that were homoplasmic for the non-Mendelian alleles from the mating-type "minus" parent. At best, weak linkage was detected between the sr-nM1 and er-nM1 loci. Non-Mendelian, chloroplast gene markers in Chlamydomonas eugametos and Chlamydomonas reinhardtii showed a predominantly uniparental mode of transmission from the mating-type "plus" parent in crosses performed under the same conditions used for the C. moewusii crosses.
A FEMALE-SPECIFIC LETHAL LESION IN AN X-LINKED POSITIVE REGULATOR OF THE DROSOPHILA SEX DETERMINATION GENE, SEX-LETHAL
Authors: Cline Thomas W 
Published: January 2021

ABSTRACT
Characterization of a partial-loss-of-function, female-specific lethal mutation has identified an X-linked genetic element (1-34.3; 10B4) that functions as a positive regulator of Sxl, a central gene controlling sex determination in Drosophila melanogaster. The name, sisterless-a, was chosen both to suggest functional similarities that exist between this gene and another positive regulator of Sxl, the maternally acting gene daughterless (da), and also to highlight an important difference; namely, that in contrast to da, it is the zygotic rather than maternal functioning of sis-a that is involved in its interaction with Sxl. As with da, the female-specific lethal phenotype of sis-a is suppressed both by SxlM #1, a gain-of-function mutant allele of the target gene, and, to a lesser extent, by a duplication of Sxl +. Mutations at sis-a, da and Sxl display female-specific dominant synergism, each enhancing the others' lethal effects. The allele specificity with respect to Sxl of these dominant interactions indicates that sis-a and da affect the same aspect of Sxl regulation. As with previous studies of da and Sxl, the masculinizing effects of loss of sis-a function are generally obscured by lethal effects, presumably related to upsets in dosage compensation. The masculinizing effects can be dissociated from lethal effects by analysis of triploid intersexes (XX AAA) or by analysis of diploid females who are also mutant for autosomal genes known to be required for the transcriptional hyperactivation associated with dosage compensation in males. Analysis of foreleg development shows that intersexuality generated by sis-a is of the mosaic type: At the level of individual cells, only male or female development is observed, never an intermediate sexual phenotype characteristic of true intersexes. Sexual development of diplo-X germline and somatic clones of sis-a tissue generated by mitotic recombination during larval stages is normal, as is the sexual phenotype of homozygous sis-a escapers. Considered in their totality, these results indicate that sis-a functions early in development to help establish the activity state of Sxl and thereby initiate the sexual pathway commitment, rather than functioning later in the processes by which Sxl maintains and expresses the sex determination decision.
INTERSTRAIN VARIATION IN AMYLASE GENE COPY NUMBER AND mRNA ABUNDANCE IN THREE MOUSE TISSUES
Authors: Meisler Miriam H , Antonucci Tammy K , Treisman Laurelee O , Gumucio Deborah L , Samuelson Linda C 
Published: January 2021

ABSTRACT
Amylase expression in strain YBR differs in several respects from the standard mouse phenotype. The synthesis of salivary amylase is elevated twofold in YBR mice and the synthesis of pancreatic amylase is reduced to one-half the normal rate. We have compared the concentrations of amylase mRNA in the parotid, liver and pancreas of YBR mice with those in strains A/J and C3H. We observed differences in amylase mRNA abundance which can account for the levels of amylase protein synthesis in the parotid and pancreas of these strains. Unexpectedly, the concentration of amylase mRNA in the liver of YBR mice was also higher than in the other strains. Since liver amylase is transcribed from the same gene as parotid amylase, duplication of the Amy-1 locus could account for the elevated mRNA concentration in both tissues. Quantitative analysis of genomic DNA by Southern blotting provided direct evidence for duplication of Amy-1 in strain YBR.
GENETIC STUDIES ON THE LOSS OF Mu MUTATOR ACTIVITY IN MAIZE
Authors: Robertson Donald S 
Published: January 2021

ABSTRACT
Mutator activity of the Mu mutator system of maize can be lost by either outcrossing or inbreeding Mu stocks. The nature of these two kinds of Mu-loss phenomena was analyzed by testing the results of crossing Mu-loss stocks by active Mu lines. Outcross-Mu-loss stocks are capable of supporting Mu activity if crossed by an active mutator line. Inbred-Mu-loss stocks, however, inactivate the active Mu system contributed by a Mu line. Also, inbred-Mu-loss lines do not regain Mu activity after at least three generations of outcrossing to non-Mu stocks. These results suggest that, once the Mu system is inactivated by inbreeding, it remains inactivated for at least three generations of outcrossing. Further, once the system responsible for inactivation is established, it will, in turn, inactivate an active Mu system contributed by crossing with Mu plants. The outcross-Mu-loss does not seem to involve such an inactivation system. These results are interpreted in the light of recent evidence that Mu inactivation results from the modification of Mu 1 transposable elements involved in the Mu phenotype.
EVALUATING QUANTITATIVE VARIATION IN THE GENOME OF ZEA MAYS
Authors: Rivin Carol J , Cullis Christopher A , Walbot Virginia 
Published: January 2021

ABSTRACT
Genomic diversity within the species Zea mays has been examined by measuring the variation in the repetitive component of the nuclear genome among North American inbred lines and varieties. This was done by preparing a set of clones of repetitive maize sequences that differ in function, molecular arrangement and multiplicity and then using these as probes for quantitative hybridization to DNA from various maize genotypes. The comparison showed that the majority of repeated sequences are markedly variable in copy number among the ten maize strains tested.—The clone sample contained the rDNA and 5S genes, the major repeat of the chromosome knobs, sequences functioning as origins of DNA replication in yeast (ARS sequences) and randomly cloned sequences of unknown function and chromosomal location. The sequences ranged in reiteration frequency from 200 to greater than 105 copies and included both tandemly arrayed and dispersed repeats. The copy numbers were measured by hybridizing labeled cloned sequences to aliquots of high molecular weight genomic DNA that were applied to nitrocellulose filters through a slotted template (slot blotting). The hybridization signal on an autoradiogram occurred in a narrow band that could be scored reliably with a densitometer. This provided a rapid method of determining the abundance of particular repeated sequences in individual plants and plant populations. Using this technique, we found that the copy number of repeated sequences of all types generally varied among the strains by two- to threefold, although at least one sequence showed no detectable variation.—In contrast to the variability found between strains, individuals within an inbred line or variety were found to be indistinguishable in terms of specific sequence multiplicity. Each genotype has a different pattern of copy numbers for the set of repeated sequence clones, and this pattern is characteristic of all individuals of a particular genotype. The data also show that the copy number of each sequence varies independently. No strains had uniformly high or low copy numbers for the entire set of probes.
RECOMBINATION BETWEEN IS5 ELEMENTS: REQUIREMENT FOR HOMOLOGY AND RECOMBINATION FUNCTIONS
Authors: Timmons Michael S , Lieb M , Deonier Richard C 
Published: January 2021

ABSTRACT
Intermolecular recombination between two IS5 elements was measured, using bacteriophage lambda recombination vectors, and was compared to recombination between two copies of an SV40 segment cloned into the same vectors. Experiments were conducted in the presence and in the absence of RecA and Red functions, and with the recombining inserts in the same or in reversed orientation. Under all conditions, IS5 elements recombined in a manner similar to the SV40 inserts, indicating that IS-encoded functions did not confer measurable additional intermolecular recombination ability to IS5 in E. coli K-12. Bacteriophages containing reversed IS5 inserts, for which the 16 base pair (bp) termini are identical in 15 positions and which display 12 bp of uninterrupted homology, recombined at approximately the same low frequency under Rec+ and Rec- conditions, indicating that these short homologies were not good substrates for the Rec system. Bacteriophages having reversed inserts recombined better under Red+ than under Red- conditions, but the crossovers were located in nonhomologous regions flanking the element termini. This suggests that 12-bp homologies are not good substrates for the Red system.
C. ELEGANS unc-105 MUTATIONS AFFECT MUSCLE AND ARE SUPPRESSED BY OTHER MUTATIONS THAT AFFECT MUSCLE
Authors: Park Eun-Chung , Horvitz H Robert 
Published: January 2021

ABSTRACT
Certain mutations in the unc-105 II gene of the nematode Caenorhabditis elegans have dominant effects on morphology and behavior: animals become small, severely hypercontracted and paralyzed. These unc-105 mutants revert both spontaneously and with mutagens at high frequencies to a wild-type phenotype. Most of the reversion events are intragenic, apparently because the null (loss-of-function) phenotype of unc-105 is wild type. One revertant defined an extragenic suppressor locus, sup-20 X. Such suppressor alleles of sup-20 are rare, and the apparent null phenotype of sup-20 is embryonic lethality. By constructing animals genetically mosaic for sup-20, we have shown that the primary effect of sup-20 is in muscle cells. In addition to mutations in sup-20, other mutations causing muscle defects, such as unc-54 and unc-22 mutations, suppress the hypercontracted phenotype of unc-105. The ease of identifying nonhypercontracted revertants of unc-105 mutants greatly facilitates the isolation of new mutants defective in muscle structure and function.