bluuebunny/crossref_metadata_2025_split huggingface dataset:
Causes of sex ratio bias may account for unisexual sterility in hybrids: a new explanation of Haldane's rule and related phenomena.
Authors: Hurst L D , Pomiankowski A 
Published: January 2021

Abstract
Unisexual hybrid disruption can be accounted for by interactions between sex ratio distorters which have diverged in the species of the hybrid cross. One class of unisexual hybrid disruption is described by Haldane's rule, namely that the sex which is absent, inviable or sterile is the heterogametic sex. This effect is mainly due to incompatibility between X and Y chromosomes. We propose that this incompatibility is due to a mutual imbalance between meiotic drive genes, which are more likely to evolve on sex chromosomes than autosomes. The incidences of taxa with sex chromosome drive closely matches those where Haldane's rule applies: Aves, Mammalia, Lepidoptera and Diptera. We predict that Haldane's rule is not universal but is correct for taxa with sex chromosome meiotic drive. A second class of hybrid disruption affects the male of the species regardless of which sex is heterogametic. Typically the genes responsible for this form of disruption are cytoplasmic. These instances are accounted for by the release from suppression of cytoplasmic sex ratio distorters when in a novel nuclear cytotype. Due to the exclusively maternal transmission of cytoplasm, cytoplasmic sex ratio distorters cause only female-biased sex ratios. This asymmetry explains why hybrid disruption is limited to the male.
Associations between DNA sequence variation and variation in expression of the Adh gene in natural populations of Drosophila melanogaster.
Authors: Laurie C C , Bridgham J T , Choudhary M 
Published: January 2021

Abstract
A large part of the genetic variation in alcohol dehydrogenase (ADH) activity level in natural populations of Drosophila melanogaster is associated with segregation of an amino acid replacement polymorphism at nucleotide 1490, which generates a difference in electrophoretic mobility. Part of the allozymic difference in activity level is due to a catalytic efficiency difference, which is also caused by the amino acid replacement, and part is due to a difference in the concentration of ADH protein. A previous site-directed in vitro mutagenesis experiment clearly demonstrated that the amino acid replacement has no effect on the concentration of ADH protein, nor does a strongly associated silent polymorphism at nucleotide 1443. Here we analyze associations between polymorphisms within the Adh gene and variation in ADH protein level for a number of chromosomes derived from natural populations. A sequence length polymorphism within the first intron of the distal (adult) transcript, 1, is in strong linkage disequilibrium with the amino acid replacement. Among a sample of 46 isochromosomal lines analyzed, all but one of the 14 Fast lines have 1 and all but one of the 32 Slow lines lack 1. The exceptional Fast line has an unusually low level of ADH protein (typical of Slow lines) and the exceptional Slow line has an unusually high level (typical of Fast lines). These results suggest that the 1 polymorphism may be responsible for the average difference in ADH protein between the allozymic classes. A previous experiment localized the effect on ADH protein to a 2.3-kb restriction fragment. DNA sequences of this fragment from several alleles of each allozymic type indicate that no other polymorphisms within this region are as closely associated with the ADH protein level difference as the 1 polymorphism.
Two genetically and molecularly distinct functions involved in early neurogenesis reside within the Enhancer of split locus of Drosophila melanogaster.
Authors: Delidakis C , Preiss A , Hartley D A , Artavanis-Tsakonas S 
Published: January 2021

Abstract
Molecular correlation of the genetic aspects of the function of the neurogenic gene Enhancer of split [E(spl)] has previously been hampered by the densely transcribed nature of the chromosomal region within which it resides. We present data indicating that two distinct molecular species contribute to E(spl) function. Analysis of new E(spl) alleles has allowed us to define two complementing functions within the locus. Subsequent phenotypic analysis of different E(spl) deficiencies combined with P element-transformed constructs has demonstrated that these two functions correspond to: (1) a family of helix-loop-helix (HLH) protein-encoding genes and (2) the single copy gene E(spl) m9/10, whose product shares homology with G-protein beta subunits. The zygotically active E(spl) HLH genes can, at least partially, substitute for one another's functions and their total copy number determines the activity of the locus. E(spl) m9/10 acts synergistically with the E(spl) HLH genes and other neurogenic genes in the process of neurogenesis. The maternal component of E(spl) m9/10 has the most pronounced effect in neurogenesis, while its zygotic component is predominantly required during postembryonic development. The lethality of trans-heterozygotes of null E(spl) deficiency alleles with a strong Delta point mutation is a result of the concomitant reduction in activity of both E(spl) HLH and m9/10 functions. Immunocytochemical localization of the E(spl) m9/10 protein has revealed that it is a ubiquitously distributed nuclear component in embryonic, larval and imaginal tissues.
swi6, a gene required for mating-type switching, prohibits meiotic recombination in the mat2-mat3 "cold spot" of fission yeast.
Authors: Klar A J , Bonaduce M J 
Published: January 2021

Abstract
Mitotic interconversion of the mating-type locus (mat1) of the fission yeast Schizosaccharomyces pombe is initiated by a double-strand break at mat1. The mat2 and mat3 loci act as nonrandom donors of genetic information for mat1 switching such that switches occur primarily (or only) to the opposite mat1 allele. Location of the mat1 "hot spot" for transposition should be contrasted with the "cold spot" of meiotic recombination located within the adjoining mat2-mat3 interval. That is, meiotic interchromosomal recombination in mat2, mat3 and the intervening 15-kilobase region does not occur at all. swi2 and swi6 switching-deficient mutants possess the normal level of double-strand break at mat1, yet they fail to switch efficiently. By testing for meiotic recombination in the cold spot, we found the usual lack of recombination in a swi2 mutant but a significant level of recombination in a swi6 mutant. Therefore, the swi6 gene function is required to keep the donor loci inert for interchromosomal recombination. This finding, combined with the additional result that switching primarily occurs intrachromosomally, suggests that the donor loci are made accessible for switching by folding them onto mat1, thus causing the cold spot of recombination.
Chromosome rearrangement by ectopic recombination in Drosophila melanogaster: genome structure and evolution.
Authors: Montgomery E A , Huang S M , Langley C H , Judd B H 
Published: January 2021

Abstract
Ectopic recombination between interspersed repeat sequences generates chromosomal rearrangements that have a major impact on genome structure. A survey of ectopic recombination in the region flanking the white locus of Drosophila melanogaster identified 25 transposon-mediated rearrangements from four parallel experiments. Eighteen of the 25 were generated from females carrying X chromosomes heterozygous for interspersed repeat sequences. The cytogenetic and molecular analyses of the rearrangements and the parental chromosomes show: (1) interchromosomal and intrachromosomal recombinants are generated in about equal numbers; (2) ectopic recombination appears to be a meiotic process that is stimulated by the interchromosomal effect to about the same degree as regular crossing over; (3) copies of the retrotransposon roo were involved in all of the interchromosomal exchanges; some copies were involved much more frequently than others in the target region; (4) homozygosis for interspersed repeat sequences and other sequence variations significantly reduced ectopic recombination.
Changes in state of the Wx-m5 allele of maize are due to intragenic transposition of Ds.
Authors: Weil C F , Marillonnet S , Burr B , Wessler S R 
Published: January 2021

Abstract
The molecular basis for the unusual phenotype conditioned by the waxy(Wx)-m5 Ds allele has been elucidated. Unlike most Ds alleles, Wx-m5 is phenotypically wild-type in the absence of Ac. We find that the Wx-m5 gene contains a 2-kb Ds element at -470 relative to the start of Wx transcription, representing the most 5' insertion of any transposable element allele characterized to date in plants. Despite its wild type phenotype, Wx-m5 has reduced levels of Wx enzymatic activity indicating that Ds insertion influences Wx gene expression. In the presence of Ac, Wx-m5 kernels have sectors of null expression on a wild-type background and give rise to stable wx and unstable wx-m germinal derivatives. Seventeen of 20 derivatives examined are wx-m alleles and at least 15 of these appear to result from intragenic transposition of Ds from -470 to new sites within the Wx gene. Three wx-m alleles contain two Ds elements, one at -470 and a second in Wx coding sequences. Surprisingly, only 3 out of 20 derivatives are stable wx mutants and these have sustained gross rearrangements of Wx and flanking sequences. For most other maize transposable element alleles somatic sectors and germinal derivatives usually arise following element excision or deletions of element sequences. In contrast, element insertion following intragenic transposition is apparently responsible for most of the somatic sectors and germinal derivatives of Wx-m5.
Size polymorphisms due to changes in the number of O-glycosylated tandem repeats in the Dictyostelium discoideum glycoprotein PsA.
Authors: Gooley A A , Marshchalek R , Williams K L 
Published: January 2021

Abstract
The molecular weight polymorphism in the Dictyostelium discoideum cell surface glycoprotein PsA is due to incremental copies of an O-glycosylated tandem tetrapeptide repeat. Allelic variation at the pspA locus results in a PsA glycoprotein with three, four or five tandem copies of Pro-Thr-Val-Thr. The simplest explanation for the origin of this polymorphism is an unequal crossing over event in the ancestral gene containing four copies. Each Thr in the tandem repeat is substituted with carbohydrate, which is completely absent from PsA in strains carrying a glycosylation defective modB mutation. Glycosylated tandem repeats appear to be a common feature of cell surface glycoproteins which are characterized by short domains rich in Pro and Thr or Ser. It is probable that the glycosylated repeat domain acts as a "spacer" peptide that projects the globular domain above the glycocalyx.
A genetic mapping system in Caenorhabditis elegans based on polymorphic sequence-tagged sites.
Authors: Williams B D , Schrank B , Huynh C , Shownkeen R , Waterston R H 
Published: January 2021

Abstract
We devised an efficient genetic mapping system in the nematode Caenorhabditis elegans which is based upon the differences in number and location of the transposable element Tc1 between the Bristol and Bergerac strains. Using the nearly completed physical map of the C. elegans genome, we selected 40 widely distributed sites which contain a Tc1 element in the Bergerac strain, but not in the Bristol strain. For each site a polymerase chain reaction assay was designed that can distinguish between the Bergerac Tc1-containing site and the Bristol "empty" site. By combining appropriate assays in a single reaction, one can score multiple sites within single worms. This permits a mutation to be rapidly mapped, first to a linkage group and then to a chromosomal subregion, through analysis of only a small number of progeny from a single interstrain cross.
On the theory of partially inbreeding finite populations. III. Fixation probabilities under partial selfing when heterozygotes are intermediate in viability.
Authors: Pollak E , Sabran M 
Published: January 2021

Abstract
In a previous paper by the senior author, an approximation to the probability of survival was given for a mutant, which is originally present in a single heterozygote, in a population that reproduces partly by selfing and partly by random mating. The population was assumed to be very large, but the result obtained is general with regard to the level of dominance in viability. In this paper two errors which were made in that earlier work are corrected. A general approximate expression is then derived for the probability that an allele A is fixed in a partially self fertilizing population of size N, if its initial frequency is p, selection is weak and heterozygotes with the allele are exactly intermediate in viability compared with genotypes AA and AA. A rigorous proof is given for a special case that is a generalization of the classical binomial sampling model. In this case, but not in general, the approximate fixation probability is independent of the probability of reproduction by selfing. Some implications are discussed.
Characterization of mutant alleles of myospheroid, the gene encoding the beta subunit of the Drosophila PS integrins.
Authors: Bunch T A , Salatino R , Engelsgjerd M C , Mukai L , West R F , Brower D L 
Published: January 2021

Abstract
This paper presents the characterization of nine alleles of myospheroid, which encodes the beta PS subunit of the Drosophila PS integrins. On Southern blots, the mysXB87, mysXN101 and mysXR04 genes yield restriction digest patterns similar to that seen for wild-type chromosomes, however the mys1 and mysXG43 genes contain detectable deletions. mys1, mysXB87 and mysXG43 make little or no stable protein product, and genetically behave as strong lethal alleles. For the mysXN101 mutation, protein product is seen on immunoblots and a reduced amount of beta PS protein is seen at muscle attachment sites of embryos; this mutant protein retains some wild-type function, as revealed by complementation tests with weak alleles. Protein is also seen on immunoblots from mysXR04 embryos, and this allele behaves as an antimorph, being more deleterious in some crosses than the complete deficiency for the locus. mysts2 and mysnj42 are typically lethal in various combinations with other alleles at high temperatures only, but even at high physiological temperatures, neither appears to eliminate gene function completely. The complementation behaviors of mysts1 and mysts3 are quite unusual and suggest that these mutations involve regulatory phenomena. For mysts3, the data are most easily explained by postulating transvection effects at the locus. The results for mysts1 are less straightforward, but point to the possibility of a chromosome pairing-dependent negative interaction.
Estimation of levels of gene flow from DNA sequence data.
Authors: Hudson R R , Slatkin M , Maddison W P 
Published: January 2021

Abstract
We compare the utility of two methods for estimating the average levels of gene flow from DNA sequence data. One method is based on estimating FST from frequencies at polymorphic sites, treating each site as a separate locus. The other method is based on computing the minimum number of migration events consistent with the gene tree inferred from their sequences. We compared the performance of these two methods on data that were generated by a computer simulation program that assumed the infinite sites model of mutation and that assumed an island model of migration. We found that in general when there is no recombination, the cladistic method performed better than FST while the reverse was true for rates of recombination similar to those found in eukaryotic nuclear genes, although FST performed better for all recombination rates for very low levels of migration (Nm = 0.1).
Maximum likelihood mapping of quantitative trait loci using full-sib families.
Authors: Knott S A , Haley C S 
Published: January 2021

Abstract
A maximum likelihood method is presented for the detection of quantitative trait loci (QTL) using flanking markers in full-sib families. This method incorporates a random component for common family effects due to additional QTL or the environment. Simulated data have been used to investigate this method. With a fixed total number of full sibs power of detection decreased substantially with decreasing family size. Increasing the number of alleles at the marker loci (i.e., polymorphism information content) and decreasing the interval size about the QTL increased power. Flanking markers were more powerful than single markers. In testing for a linked QTL the test must be made against a model which allows for between family variation (i.e., including an unlinked QTL or a between family variance component) or the test statistic may be grossly inflated. Mean parameter estimates were close to the simulated values in all situations when fitting the full model (including a linked QTL and common family effect). If the common family component was omitted the QTL effect was overestimated in data in which additional genetic variance was simulated and when compared with an unlinked QTL model there was reduced power. The test statistic curves, reflecting the likelihood of the QTL at each position along the chromosome, have discontinuities at the markers caused by adjacent pairs of markers providing different amounts of information. This must be accounted for when using flanking markers to search for a QTL in an outbred population.
Intraclass and interclass correlations of allele sizes within and between loci in DNA typing data.
Authors: Chakraborty R , Srinivasan M R , de Andrade M 
Published: January 2021

Abstract
Nonparametric measures of correlations of DNA fragment lengths within and between variable number of tandem repeat (VNTR) loci are proposed to test the hypothesis of random association of allele sizes at VNTR loci. Transformations of these nonparametric correlation measures are suggested to detect deviations of their null expectations caused by population subdivision and errors of measurement of VNTR fragment lengths. Analytic and permutation-based computer simulation studies are performed to show that under the hypothesis of independence of allele sizes the transformed correlation measures are normally distributed, irrespective of the VNTR fragment size distribution in the population even when the number of individuals samples is as low as 100. Power calculations are performed to establish that the current population data on six VNTR loci in the US Hispanic sample are in accordance with the hypothesis of random association of allele sizes within and between loci. Implications of these results in the context of forensic use of DNA typing are also discussed.
The Cs sec mutants of Escherichia coli reflect the cold sensitivity of protein export itself.
Authors: Pogliano K J , Beckwith J 
Published: January 2021

Abstract
We have found that temperature can have a striking effect upon protein export in Escherichia coli, suggesting that there is a cold-sensitive step in the protein export pathway. Cs mutations comprise the largest class of mutations affecting the membrane-localized Sec proteins SecD, SecE, SecF and SecY. Although some of these mutations could encode cold-labile proteins, this is unlikely to account for the Cs phenotype of most export mutants, as mutations which simply produce lower amounts of SecE protein have the same phenotype. Certain signal sequence mutations affecting maltose binding protein are also cold sensitive for export. These effects appear to arise by a specific interaction of cold with certain export defects. We believe that the Cs sec mutations are representative of a large class of conditional lethal mutations, whose conditional phenotype reflects an underlying thermal sensitivity of the process in which they are involved.
Genetic evidence that the meiotic recombination hotspot at the HIS4 locus of Saccharomyces cerevisiae does not represent a site for a symmetrically processed double-strand break.
Authors: Porter S E , White M A , Petes T D 
Published: January 2021

Abstract
In the yeast Saccharomyces cerevisiae, the binding of the Rap1 protein to a site located between the 5' end of the HIS4 gene and the 3' end of BIK1 stimulates meiotic recombination at both flanking loci. By using strains that contain mutations located in HIS4 and BIK1, we found that most recombination events stimulated by the binding of Rap1 involve HIS4 or BIK1, rather than bidirectional events including both loci. The patterns of aberrant segregation indicate that most of the Rap1-stimulated recombination events do not represent the symmetric processing of a double-strand DNA break located at the Rap1-binding site.
Inheritance of the morphological differences between maize and teosinte: comparison of results for two F2 populations.
Authors: Doebley J , Stec A 
Published: January 2021

Abstract
Molecular marker loci (MMLs) were employed to map quantitative trait loci (QTLs) in an F2 population derived from a cross of maize (Zea mays ssp. mays) and its probable progenitor, teosinte (Z. mays ssp. parviglumis). A total of 50 significant associations (putative QTLs) between the MMLs and nine key traits that distinguish maize and teosinte were identified. Results from this analysis are compared with our previous analysis of an F2 population derived from a cross of a different variety of maize and another subspecies of teosinte (Z. mays ssp. mexicana). For traits that measure the architectural differences between maize and teosinte, the two F2 populations possessed similar suites of QTLs. For traits that measure components of yield, substantially different suites of QTLs were identified in the two populations. QTLs that control about 20% or more of the phenotypic variance for a trait in one population were detected in the other population 81% of the time, while QTLs that control less than 10% of the variance in one population were detected in the other population only 28% of the time. In our previously published analysis of the maize x ssp. mexicana population, we identified five regions of the genome that control most of the key morphological differences between maize and teosinte. These same five regions also control most of the differences in the maize x ssp. parviglumis population. Results from both populations support the hypothesis that a relatively small number of loci with large effects were involved in the early evolution of the key traits that distinguish maize and teosinte. It is suggested that loci with large effects on morphology may not be a specific feature of crop evolution, but rather a common phenomenon in plant evolution whenever a species invades a new niche with reduced competition.