bluuebunny/crossref_metadata_2025 huggingface dataset:
Presence of abnormal synaptonemal complexes in heterothallic species of Neurospora
Authors: Bojko Maja
Published: April 2011

Synaptonemal complex abnormalities are frequent in reconstructed meiotic prophase nuclei of Neurospora crassa and Neurospora intermedia. Three kinds of synaptonemal complex anomalies were seen: lateral component splits, lateral component junctions, and multiple complexes. The anomalies apparently are formed during or after the pairing process, as they were not seen in the largely unpaired early zygotene chromosomes. Their presence at all the other substages from mid-zygotene to late pachytene indicates that they are not eliminated before the synaptonemal complex decomposes at diplotene. Abnormal synaptonemal complexes were seen in all 19 crosses of N. crassa and N. intermedia that were examined, including matings between standard laboratory strains, inversions, Spore killers, and strains collected from nature. The frequency of affected nuclei and degree of abnormality within a nucleus varied in different matings. No abnormalities were present in the homothallic species Neurospora africana and Neurospora terricola. Structural chromosome aberrations, introgression, and heterozygosity have been eliminated as causes for pairing disorder. The abnormal synaptonemal complexes seemingly do not interfere with normal ascus development and ascospore formation. The affected nuclei are not aborted during meiotic prophase, nor are they eliminated by abortion of mature asci. The abnormal meiocytes do not lead to aneuploidy, as judged by the low frequency of white ascospores in crosses between wild type strains that have many abnormalities. Thus, the abnormal synatonemal complexes do not appear to prevent chiasma formation between homologues.Key words: Neurospora, meiosis, synaptonemal complex.
Homology of Agaricus mitochondrial plasmids with mitochondrial DNA
Authors: Meyer Robert J. , Hintz William A. , Mohan Madan , Robison Mary , Anderson James B. , Horgen Paul A.
Published: April 2011

A strain of Agaricus bitorquis (Ag4) contains two linear plasmids, pEM and pMPJ. Restriction maps for these two plasmids were determined. Similar plasmid-like DNAs were found to be present in some other strains of A. bitorquis but none were found in strains of the commercial mushroom Agaricus bisporus. The three internal EcoRI fragments of pEM were cloned into a bacterial plasmid and were subsequently used as hybridization probes. The cloned portion of pEM has homology with sequences present in the mitochondrial genome of strains of A. bisporus and A. bitorquis, even those without pEM or any obvious extrachromosomal element. In addition, there are pEM homologous sequences within the mitochondrial genome of the source strain Ag4, which contain pEM and pMPJ as extrachromosomal elements.Key words: Agaricus, plasmid, mitochondrial DNA.
Complex organization of the length heterogeneous 5′ external spacer of mung bean (Vigna radiata) ribosomal DNA
Authors: Gerstner Jutta , Schiebel Katrin , Waldburg Georg von , Hemleben Vera
Published: April 2011

Restriction enzyme analysis and cloning of the 18S, 5.8S, and 25S ribosomal RNA genes (rDNA) of the mung bean (Vigna radiata = Phaseolus aureus) reveal length heterogeneity in the repeating units (10 – 11 kbp) localized within two different regions in the ribosomal spacer. The 1.5 – 2.0 kbp region flanking the 3′ end of the 25S rRNA contains various numbers (8 – 10) of tandemly arranged 180 bp subrepeats. After DNA sequencing a complex organized length heterogeneous 5′ external spacer built up of different numbers of 340 bp subrepeats, each flanked by 52 bp direct repeats, is detected and described for the first time for plant ribosomal DNA repeating units. Sequences occurring in front of and within this repeated structure (elements II – IV) can be combined with the motifs P1, P2, and P3. These exhibit a strong similarity to transcription initiation sites specific for RNA polymerase I described for other plant and animal rDNA investigated to date. Transcription products complementary to the complex repeated structures are detected by hybridization to total nuclear RNA. The 9 bp element V located in front of the first 340 bp region appears in duplicated form as a direct repeat with sequence similarity to SV40 (or RNA polymerase II) enhancer sequences.Key words: promoter, ribosomal RNA genes, RNA polymerase I, spacer organization, transcription.
Genomic instability in a clonal species, Tradescantia commelinoides (Commelinaceae)
Authors: Kenton Ann , Langton David , Coleman Janet
Published: April 2011

Within a population of Tradescantia commelinoides collected in the wild, genomic instability is unique to clones having large centric shifts. Initially, the instability is attributable to breakage caused by imperfect separation of abnormally long chromatids, but the more severe effects that sometimes develop are a consequence of spontaneous breakage and reunion and disturbance of control mechanisms. Breakage of excessively long chromatids following repositioning of the centromere may destabilize some segment of DNA important for ordered replication and division. Eventual stability would result from the loss of this segment, or its transfer to a quiescent position. A period of instability, leading to the establishment of a new equilibrium, may represent an important source of variability in species that rely heavily upon vegetative reproduction for their colonizing potential.Key words: Tradescantia, clonal species, centric shift, genomic instability, karyotype orthoselection.
Cytological studies of Blattella germanica and Blattella asahinai. I. A possible genetic basis of interspecific divergence
Authors: Ross Mary H.
Published: April 2011

The position of the nucleolus organizing region (NOR) in Blattella asahinai differs from that in its close relative, Blattella germanica. The number and position of NORs in hybrid males from reciprocal crosses indicate that the NOR carried by the X chromosome of B. germanica corresponds to a small, paired, terminal segment on the longest chromosome (No. 12) in B. asahinai. The segment is not present in B. germanica; hybrids are heterozygous for the segment. Except for these differences and a relatively smaller size of the B. asahinai X chromosome, gross chromosome morphology is essentially identical in the two species and their hybrids. The size of the X and position of the NORs in hybrid males were as expected according to the direction of the cross. The observations are clearly indicative of a nonreciprocal translocation involving the NOR on the X chromosome of B. germanica and those on an autosome of B. asahinai. The shift involved genes fundamental to protein synthesis, i.e., rDNA (identified by association with the nucleoli). Even minor effects on these genes could bring about significant changes in an organism. It is suggested that the translocation may have been the genetic mechanism of interspecific divergence.Key words: cockroach, evolution, nucleolus, NOR chromosomes.
Genes controlling malathion resistance in a laboratory-selected population of Drosophila melanogaster
Authors: Houpt D. R. , Pursey J. C. , Morton R. A.
Published: April 2011

The chromosomal locations of several genes responsible for increased malathion resistance in a laboratory-selected population of Drosophila melanogaster have been determined. These genes appear to be involved in the regulation of microsomal cytochrome P-450. A major gene on chromosome 2 (2-64) and at least two genes on chromosome 3 (near 3-58) control increased mixed function oxidase activity, and both larval and adult malathion resistance. Although the chromosome 2 locus was not associated with a significant increase in cytochrome P-450 content, SDS polyacrylamide gel electrophoresis of microsomal proteins detected increased silver staining of a polypeptide having a relative molecular mass (Mr) of about 52 000. Microsomes from strains carrying the chromosome 3 factors for resistance contained more cytochrome P-450 and increased amounts of two heme-staining protein bands (Mr = 50 000 and 54 000). The genes regulating these proteins were closely linked to striped at 3-62 and probably identical to the loci responsible for malathion resistance and increased mixed function oxidase activity. Other R genes on both chromosomes 2 and 3 as well as target resistance were required for the full expression of malathion resistance in the selected Drosophila population. Exposure of this Drosophila melanogaster population to malathion selected a polygenic system for the oxidative metabolism of insecticide.Key words: insecticide resistance, mixed-function oxidase, cytochrome P-450, Drosophila melanogaster.
Assays of testis development in the mouse distinguish three classes of domesticus-type Y chromosome
Authors: Biddle Fred G. , Nishioka Yutaka
Published: April 2011

The Y chromosome of Mus musculus poschiavinus interacts with the autosomal recessive gene tda-1b of the C57BL/6J laboratory strain of the house mouse to cause complete or partial sex reversal. Ovaries or ovotestes develop in a substantial proportion of the XY fetuses. Several different Y-specific DNA probes distinguish two major types of Y chromosome in the house mouse and they are represented by M. m. domesticus and M. m. musculus. The poschiavinus Y chromosome appears identical to the domesticus Y. The developmental distribution of the gonad types was examined in the first backcross or N2 generation of fetuses in C57BL/6J with six different domesticus-type Y chromosomes and, as controls, three different musculus-type Y chromosomes. Gonadal hermaphrodites were found with three of the six domesticus-type Y chromosomes. Both overall frequency and phenotypic distribution of types of gonadal hermaphrodites identify three classes of domesticus-type Y chromosome by their differential interaction with the C57BL/6J genetic background.Key words: mouse, Y chromosomes, gonadal hermaphrodites, primary sex determination.
Cytology of Elymus panormitanus and its F1 hybrids with Pseudoroegneria spicata, Elymus caninus, and Elymus dentatus ssp. ugamicus
Authors: Jensen Kevin B. , Hatch Stephan L.
Published: April 2011

Three accessions of Elymus panormitanus (Parl.) Tzvelev were introduced into the United States in 1967 from Iraq and Turkey. A study was undertaken to describe the cytological behavior, mode of reproduction, cytology and fertility of E. panormitanus and its F1 hybrids with "analyzer" species, and genomic formula. Chromosome pairing was studied at meta-phase I in a series of interspecific and intergeneric hybrids to characterize the genomic constitution of E. panormitanus. All plants of E. panormitanus studied were 2n = 28, and averaged 13.96 bivalents per cell, suggesting that E. panormitanus is an allotetraploid with two different genomes. Seed set under controlled pollination indicated that E. panormitanus is highly self-compatible. Hybrids between E. panormitanus and the following analyzer species (with known genomic constitution) were obtained: Pseudoroegneria spicata (Pursh.) A. Love, 2n = 14, SS; Elymus caninus (L.) L., 2n = 28, SSHH; Elymus dentatus (Hook, f.) Tzvelev ssp. ugamicus (Drob.) Tzvelev, 2n = 28, SSYY. All hybrids were highly sterile. Hybrids between E. panormitanus and P. spicata, E. caninus, and E. dentatus ssp. ugamicus averaged 3.93, 3.70, and 7.28 bivalents per cell, respectively. Meiotic data in this series of F1 hybrids and karyotype analysis of E. panormitanus suggested that the genomic formula for E. panormitanus can tentatively be written as SpSpYpYp, indicating that both genomes are modified forms of the S and Y genomes found in the East Asian SY polyploids.Key words: Triticeae, Elymus, phylogeny, hybrids, intergeneric.
Orientation and segregation of Robertsonian trivalents in Dichroplus pratensis (Acrididae)
Authors: Bidau Claudio J. , Mirol Patricia M.
Published: April 2011

Pairing behavior, metaphase I orientation, and anaphase I segregation of centric fusion trivalents were studied in 26 single, 15 double, and 2 triple male fusion heterozygotes of the polymorphic South American melanopline grasshopper Dichroplus pratensis. They represent the seven different fusions and their combinations already described in different populations of the species. Our analysis showed the following: (1) pairing behavior is very regular in all trivalents; (2) frequencies of linear orientation was very low irrespective of the trivalent involved; (3) reorientation seems to occur frequently since frequencies of abnormal segregation and aneuploid second division cells were invariably lower than those of nonconvergent orientation; (4) aneuploidy and abnormal sperm production increases with increasing number of fusions; (5) chiasma frequency and localisation is relevant to trivalent orientation since trivalents with nonconvergent orientations showed proximal and interstitial chiasmata more frequently than convergently oriented ones. The results are in agreement with the hypothesis that these polymorphisms are old and stable, and confirm that for the maintenance of a balanced polymorphism, if this polymorphism is adaptive because of its consequences on recombination, position effects, etc., changes tending to stabilise trivalent orientation and segregation are central.Key words: Dichrophus pratensis, grasshopper, Robertsonian trivalent, meiotic orientation, meiotic segregation.
The human recombination strand exchange process
Authors: Moore Sharonp P. , Rich Alexander , Fishel Richard
Published: April 2011

A mechanism for the initiation of general recombination that involves the formation of left-handed Z-DNA heteroduplex segments adjacent to right-handed B-DNA heteroduplex segments is discussed. The paranemic nature of this initiation structure allows for homology recognition in the absence of strand cleavage. This model suggests that proteins catalyzing recombination initiation via the formation of paranemic joint should in some capacity recognize Z-DNA. Other studies have shown that both the RecA protein of Escherichia coli and the Rec1 protein of Ustilago maydis have a greater affinity for Z-DNA than B-DNA. Here we have used Z-DNA affinity chromatography to purify a peptide of approximately 120 kilodaltons from a human tumor cell line that catalyzes a simple recombination strand-transfer reaction similar to one developed for the characterization of the RecA and Rec1 proteins. We report details of the characterization of the human strand-transfer activity and identified a potential human recombination complex.Key words: Z-DNA, recombination initiation, human strand-transfer activity.
Genetic control of chromosome synapsis in yeast meiosis
Authors: Giroux Craig N. , Dresser Michael E. , Tiano Howard F.
Published: April 2011

Both meiosis-specific and general recombination functions, recruited from the mitotic cell cycle, are required for elevated levels of recombination and for chromosome synapsis (assembly of the synaptonemal complex) during yeast meiosis. The meiosis-specific SPO11 gene (previously shown to be required for meiotic recombination) has been isolated and shown to be essential for synaptonemal complex formation but not for DNA metabolism during the vegetative cell cycle. In contrast, the RAD52 gene is required for mitotic and meiotic recombination but not for synaptonemal complex assembly. These data suggest that the synaptonemal complex may be necessary but is clearly not sufficient for meiotic recombination. Cytological analysis of spread meiotic nuclei demonstrates that chromosome behavior in yeast is comparable with that observed in larger eukaryotes. These spread preparations support the immunocytological localization of specific proteins in meiotic nuclei. This combination of genetic, molecular cloning, and cytological approaches in a single experimental system provides a means of addressing the role of specific gene products and nuclear structures in meiotic chromosome behavior.Key words: synaptonemal complex, chromosome behavior, meiosis.
Gap formation is associated with methyl-directed mismatch correction under conditions of restricted DNA synthesis
Authors: Su Shin-San , Grilley Michelle , Thresher Randy , Griffith Jack , Modrich Paul
Published: April 2011

A covalently closed, circular heteroduplex containing a G – T mismatch and a single hemimethylated d(GATC) site is subject to efficient methyl-directed mismatch correction in Escherichia coli extracts when repair DNA synthesis is severely restricted by limiting the concentration of exogenously supplied deoxyribonucleoside-5′-triphosphates or by supplementing reactions with chain-terminating 2′,3′-dideoxynucleoside triphosphates. However, repair under these conditions results in formation of a single-strand gap in the region of the molecule containing the mismatch and the d(GATC) site. These findings indicate that repair DNA synthesis required for methyl-directed correction can initiate in the vicinity of the mispair, and they are most consistent with a repair reaction involving 3′ → 5′ excision (or strand displacement) from the d(GATC) site followed by 5′ → 3′ repair DNA synthesis initiating in the vicinity of the mismatch.Key words: DNA repair, gene conversion, mismatch correction, mutagenesis.
Plasmon diversity in Triticum and Aegilops and its implication in wheat evolution
Authors: Tsunewaki Koichiro
Published: April 2011

Recent results on the plastome, chondriome, and plasmon diversity among Triticum (wheat) and Aegilops species have been reviewed. As to the plastome diversity, 17 different chloroplast DNA types were found among 32 species (42 accessions in total) by restriction endonuclease analysis of chloroplast DNA. Referring to the physical map of common wheat chloroplast DNA, 46 plastome mutations have been identified, and based on the number of the mutations detected between every pair of the plastomes, their phylogenetic tree has been constructed. Complete base sequence of five rbcL genes encoding rubisco large subunit, which were isolated from five different plastomes, clarified the amino acid differences that are responsible for the electrophoretic difference between the H- and L-type large subunits. A phylogenetic tree was constructed for these genes, including their flanking regions, based on the number of mutations observed between them. This tree closely resembled the phylogenetic tree of their carrier plastomes, except in one minor point. As to the chondriome diversity, both the restriction endonuclease analysis and restriction fragment length polymorphism analysis of mitochondrial DNA demonstrated higher variability of mitochondrial DNA than chloroplast DNA, proving its usefulness in elucidation of the plasmon differentiation between closely related species or even within a species. Plasmon diversity revealed by comparing phenotypes of eu- and allo-plasmic lines of emmer, timopheevi, or common wheat indicated that all characters observed are affected by alien plasmons, among which male sterility, pistillody, haploid parthenogenesis, prematurity sprouting, variegation, and growth depression are specifically expressed by different genome–plasmon interactions. Nuclear genes responsible for their expression are determined in limited cases. As to the intraspecific variation of the plasmon, Aegilops speltoides showed large intraspecific variation, whereas two wild tetraploid wheats, Triticum dicoccoides and Triticum araraticum, revealed little variation. Aegilops triuncialis was dimorphic and proved to have originated from the reciprocal crosses between Aegilops caudata and Aegilops umbellulata. Combining all the data available, the plasmon in Triticum and Aegilops species has been classified into 16 types. Plasmon diversity decreases with the increase in the ploidy. Among the diploids, differentiation of the plasmon is paralleled with that of the nuclear genome. Origin of the plasmon of most polyploid species has been determined definitely, and for the remaining, their plasmon origin could be postulated. Thus, the maternal lineage of the species in these two genera has been clarified to a great extent.Key words: Triticum, Aegilops, plasmon, plastome, chondriome, rbcL gene, variation, phylogeny, maternal lineage, restriction endonuclease analysis, restriction fragment length polymorphism analysis, base sequencing, alloplasmic wheat, phenotypic effect.
Linear plasmids that integrate into mitochondrial DNA in Neurospora
Authors: Bertrand H. , Griffiths A. J. F.
Published: April 2011

In some field isolates of Neurospora from Hawaii and India, senescence is induced by integration of linear DNA plasmids, kalilo and maranhar, respectively, into mitochondrial (mt) DNA. Although the two plasmids show little homology at the DNA level, both have inverted long terminal repeats, and each potentially encodes a DNA polymerase and a RNA polymerase. Both plasmids generate very long inverted repeats of mtDNA at their ends upon integration into mitochondrial chromosomes. Hence, they appear to integrate by a mechanism that involves pairing of both ends of the plasmid with short stretches of homologous nucleotide sequences in mtDNA. This recombinogenic association apparently generates an origin for an unscheduled round of replication of mtDNA. In the process, the resulting two copies of the mitochondrial chromosome are joined to opposite ends of the plasmid. A model for the senescence-associated accumulation of mtDNAs with plasmid insertion sequences is proposed on the basis of common features that characterize senescence in a variety of filamentous fungi.Key words: Neurospora, senescence, plasmids, mitochondria.
Rearrangements in maize mitochondrial genes
Authors: Fragoso Lino L. , Nichols Scott E. , Levings III Charles S.
Published: April 2011

Recombination is a significant cause of maize mitochondrial gene mutations. Chimeric genes are often found in the mitochondria of cytoplasmic male-sterile maize. They are created by rearrangements involving intramolecular and intermolecular recombination. Herein we describe the effect of rearrangements on the chromosomal location, flanking and coding regions of several maize mitochondrial genes.Key words: recombination, organelle, chimeric genes.
Role of gene duplication in evolution
Authors: Ohta Tomoko
Published: April 2011

It is now known that many multigene and supergene families exist in eukaryote genomes: multigene families with uniform copy members like genes for ribosomal RNA, those with variable members like immunoglobulin genes, and supergene families such as those for various growth factor and hormone receptors. Many such examples indicate that gene duplication and subsequent differentiation are extremely important for organismal evolution. In particular, gene duplication could well have been the primary mechanism for the evolution of complexity in higher organisms. Population genetic models for the origin of gene families with diverse functions are presented, in which natural selection favors those genomes with more useful mutants in duplicated genes. Since any gene has a certain probability of degenerating by mutation, success versus failure in acquiring a new gene by duplication may be expressed as the ratio of probabilities of spreading of useful versus detrimental mutations in redundant gene copies. Also examined are the effects of gene duplication on evolution by compensatory advantageous mutations. Results of the analyses show that both natural selection and random drift are important for the origin of gene families. In addition, interaction between molecular mechanisms such as unequal crossing-over and gene conversion, and selection or drift is found to have a large effect on evolution by gene duplication.Key words: gene duplication, gene family, evolution of new genes.
Model systems for aging research: syncretic concepts and diversity of mechanisms
Authors: Reis Robert J. Shmookler
Published: April 2011

A variety of very different phenomena have been subsumed under the heading of "aging" research. A review of recent experimental data, in several of the best-studied model systems for the investigation of aging, indicates that molecular changes which are putative or demonstrated proximal causes of senescent deterioration are generally not shared by other systems examined. It is thus argued that different aberrant biochemical processes have evolved as the "weakest link" limiting longevity or intermeiotic interval in different systems, although in each case the germ line must be exempted.Key words: aging, senescence, meiosis, DNA, RNA.
Polymerases and UV mutagenesis in Escherichia coli
Authors: Bridges B. A. , Bates Helen , Sharif Firdaus
Published: April 2011

Evidence for and against the involvement of the known nucleic acid polymerases in UV mutagenesis in Escherichia coli is reviewed. There is no evidence that rules out the participation of any of them when they are present but only one, the α subunit of DNA polymerase III holoenzyme (polC gene product) has been shown to be essential. It is argued that the PolC protein that functions in UV mutagenesis may not be immediately recognizable as one of the normal cellular polymerases or polymerase complexes.Key words: polymerases, ultraviolet light, mutagenesis, DNA repair, misincorporation.
Repair of base–base mismatches in simian and human cells
Authors: Brown Thomas C. , Jiricny Josef
Published: April 2011

Mismatched heteroduplexes arise as intermediates of several dissimilar genetic processes. The outcome of these genetic events will therefore be influenced by the efficiency and specificity of mismatch repair. We have studied the correction of base–base mispairs in simian and human fibroblasts by transfecting the cells with derivatives of SV40 DNA, each harboring a single mispair in a defined orientation. Analysis of plaques revealed that correction efficiencies for homomispairs followed the pattern G∙G > C∙C ≥ A∙A > T∙T. Repair bias was influenced by flanking sequences. Correction efficiencies for heteromispairs followed the pattern of G∙T > A∙C > C∙T > A∙G and repair favored the retention of G+C by a substantial margin. This repair specificity could lead to a gene conversion bias favoring the accumulation of G+C in sequences subject to high levels of recombination or unequal exchange.Key words: DNA repair, gene conversion, recombination, DNA methylation.
Amino acid similarities to other proteins offer insights into roles of UmuD and UmuC in mutagenesis
Authors: Battista John R. , Nohmi Takehiko , Donnelly Caroline E. , Walker Graham C.
Published: April 2011

The products of the umuD and umuC genes are required for most uv and chemical mutagenesis in Escherichia coli. The genes are organized in an operon that is repressed by LexA and regulated as part of the SOS response. The umuD protein shares homology with the carboxyl-terminal domain of LexA. Genetic evidence now indicates that RecA-mediated cleavage activates UmuD for its role in mutagenesis. The COOH-terminal fragment of UmuD is both necessary and sufficient for this role. Similarities of UmuD to gene 45 protein of bacteriophage T4 and of UmuC to gene 44 protein and gene 62 protein suggest possible roles for UmuD and UmuC in mutagenesis that are supported by preliminary evidence.Key words: RecA, UmuD, UmuC, bacteriophage T4, DNA accessory proteins.
Developmental genetics of the wing vein pattern of Drosophila
Authors: Díaz-Benjumea J. , Gaitán M. A. F. González , García-Bellido A.
Published: April 2011

The developmental study of the wing disc in Drosophila has revealed the progressive appearance of heterogeneities in the anlage formation i.e., of symmetric compartments, of lineage restrictions for vein and intervein regions within compartments, and in mitotic waves. The genetic analysis of alleles in 28 loci that affect vein formation allows us to classify them, according to their phenotypic effects in mutant combinations, in several groups of synergism. These effects include changes in vein differentiation, vein pattern, and growth of the wing anlage. Clonal analyses of mutations of these groups shows that pattern differentiation is associated with changes in cell proliferation dynamics. The study of combinations of mutations from different groups allows us to infer the existence of distinct genetic operations in wing development. A model is presented relating these genetic operations to cell proliferation and cell communication in wing morphogenesis and vein patterning.Key words: pattern formation, morphogenesis, cell proliferation and differentiation.
T cell receptors in autoimmune disease as targets for immune intervention
Authors: Acha-Orbea Hans , Steinman L. , McDevitt H. O.
Published: April 2011

The optimal form of treatment for an autoimmune disease should be highly specific, have few side effects, and allow treatment of clinically apparent disease. One target that could fulfill these requirements is the T cell receptor. To answer the question whether treatment of autoimmune disesase is possible with anti-T cell receptor antibodies, the heterogeneity of T cell receptor elements utilized in the T cell mediated autoimmune disease experimental allergic encephalomyelitis was analyzed. The limited heterogeneity of these elements allowed prevention and treatment of clinical autoimmune disease with anti-T cell receptor monoclonal antibodies. These results and their potential value for other autoimmune diseases are discussed.Key words: T cell receptor, autoimmune disease, monoclonal antibody therapy, experimental allergic encephalomyelitis.
Expression of the small heat shock genes during Drosophila development: comparison of the accumulation of hsp23 and hsp27 mRNAs and polypeptides
Authors: Pauli Daniel , Arrigo André-Patrick , Vazquez Julio , Tonka Chia-Hua , Tissières Alfred
Published: April 2011

Seven heat shock genes are clustered within 15 kilobases of DNA at the Drosophila melanogaster chromosomal site 67B. They show a complex pattern of expression in the absence of external stress during normal development of this organism. In this paper, we quantitatively compare the abundance of the messenger RNAs for these seven genes at all major stages of Drosophila development and then focus on hsp23 and hsp27 for which available antibodies allow the comparison between the accumulation of the mRNAs and that of their corresponding polypeptides. Transcripts for both genes are maximally abundant in white prepupae. We observe that the amount of hsp23 message decreases more rapidly than that of hsp27 mRNA throughout the pupal period. The maximal abundance of the proteins occurs at the middle of the pupal stage, when their corresponding RNAs have almost completely disappeared. The peaks of expression of the proteins are also broader than those of their transcripts, indicating that the half-lives of the polypeptides are longer. These observations suggest that complex mechanisms regulate the expression of the small heat shock genes during Drosophila development.Key words: Drosophila, development, heat shock, heat shock proteins, heat shock RNA.
From somatic variation to variant plants: mechanisms and applications
Authors: Larkin P. J. , Banks P. M. , Bhati R. , Brettell R. I. S. , Davies P. A. , Ryan S. A. , Scowcroft W. R. , Spindler L. H. , Tanner G. J.
Published: April 2011

Plants from cell cultures show a high incidence of mutation. The causes of somaclonal variation are unknown, but the genetic consequences have been analysed. A range of genetic events are responsible, including single base changes; altered gene copy number; altered expression of multigene families; chromosome fragment interchanges; and mobilisation of transposable elements. Recent applications of these phenomena are discussed in this paper, for example, in vitro selection, somaclonal variation for agronomic traits, and limited gene transfer from cultured sexual and somatic hybrids. Research is outlined attempting to use high frequency chromosomal interchanges in wheat cell cultures to introgress genes from alien chromosomes. Two examples are cereal cyst nematode resistance on a rye chromosome and barley yellow dwarf resistance on a Thinopyrum chromosome. Some presumptive introgressed lines show selfed and backcross segregations, suggesting that the resistance, but not other alien markers, is now on a wheat chromosome.Key words: somaclonal variation, introgression, somatic hybridization, chromosome rearrangement, in vitro selection.
The genomics of long tandem arrays of satellite DNA in the human genome
Authors: Willard Huntington F.
Published: April 2011

At least 10% of DNA in the human genome consists of long arrays of repeated sequences, arranged in tandem head-to-tail arrays in a number of discrete, highly localized chromosomal regions. Different families of these so-called "satellite DNA" sequences have been defined, organized in diverged subsets on different chromosomes. The molecular, cytogenetic, and evolutionary analysis of the hierarchical organization of such sequences in the human and other complex genomes encompasses a variety of approaches, including chromosomal mapping, in situ hybridization, genetic linkage analysis, long-range restriction mapping, and DNA sequencing. Investigation of the organization of satellite arrays constitutes a necessary first step towards eventual elucidation of the origin, evolution, and maintenance of these sequences and their contribution to the structure and behavior of human chromosomes.Key words: human genome, satellite DNA, chromosomes, genome analysis.
Organization of human class I homeobox genes
Authors: Boncinelli Edoardo , Acampora Dario , Pannese Maria , D'Esposito Maurizio , Somma Renato , Gaudino Giovanni , Stornaiuolo Anna , Cafiero Mauro , Faiella Antonio , Simeone Antonio
Published: April 2011

We report the genomic organization of 20 human class I homeoboxes and the predicted primary sequence of the encoded homeodomains. These homeoboxes are clustered in four complex HOX loci on chromosomes 2, 7, 12, and 17. The homeoboxes of one HOX locus can be aligned to the homeoboxes of the other HOX loci so that corresponding homeodomains in all loci can share the maximal peptide sequence identity. This correspondence of individual homeoboxes in different chromosomal loci suggests the hypothesis of large-scale duplications of a single complex locus. The existence of an ancestral complex locus might have predated the divergence of vertebrates and invertebrates.Key words: development, homeobox, gene evolution.
The role of a conserved dodecamer sequence in yeast mitochondrial gene expression
Authors: Butow Ronald A. , Zhu Hong , Perlman Philip , Conrad-Webb Heather
Published: April 2011

All mRNAs on the yeast mitochondrial genome terminate at a conserved dodecamer sequence 5′-AAUAAUAUUCUU-3′. We have characterized two mutants with altered dodecamers. One contains a deletion of the dodecamer at the end of the var1 gene, and the other contains two adjacent transversions in the dodecamer at the end of the reading frame of fit1, a gene within the ω+ allele of the 21S rRNA gene. In each mutant, expression of the respective gene is blocked completely. A dominant nuclear suppressor, SUV3-1, was isolated that suppresses the var1 deletion but is without effect on the fit1 dodecamer mutations. Unexpectedly, however, we found that SUV3-1 blocks expression of the wild-type fit1 allele by blocking processing at its dodecamer. SUV3-1 has pleiotropic effects on mitochondrial gene expression, affecting RNA processing, RNA stability, and translation. Our results suggest that RNA metabolism and translation may be part of a multicomponent complex within mitochondria.Key words: mitochondria, yeast, mRNA, RNA processing, 3′ dodecamer.
Genetic resource management of fish
Authors: Lannan James E. , Gall Graham A. E. , Thorpe John E. , Nash Colin E. , Ballachey Brenda E.
Published: April 2011

The diverse global ichthyofauna represents a wealth of genetic resources for adaptive evolution, for the development and harvest of present and future sources of human foods, and for germ plasm for aquaculture. Fish make an important contribution to human nutrition worldwide and the demand for fisheries products is increasing. Several production systems are employed in producing and harvesting fisheries products, including capture fisheries, aquaculture, and culture-based fisheries. There are risks of losing genetic variation inherent in each production system. However, genetic considerations are not widely applied to the management of fisheries. It is imperative that global strategies for the conservation of fish genetic resources be developed and implemented to ensure the richness of diversity for future generations.Key words: fish, genetic resources, management, fisheries.
Trypanotolerance and the value of conserving livestock genetic resources
Authors: Trail J. C. M. , D'Ieteren G. D. M. , Teale A. J.
Published: April 2011

Studies have been made in two main areas of genetic research on African trypanotolerant (N'Dama) cattle. The first is of the significance for performance and the heritability of trypanotolerance traits and the second is the search for markers of the breed type and the traits of interest. Results demonstrate significant effects of the ability of an animal to control parasitaemia and anaemia on its performance. Initial estimates suggested that parasitaemia measures had a very low heritability, but ability to maintain packed cell volume levels when detected as parasitaemic and to generate an immune response could form the basis of a practical selection approach. The search for markers has so far concentrated on the major histocompatibility complex and on a polymorphic system of common leukocyte antigens. Phenotypes that appeared more characteristic of the N'Dama in comparison with those of East African zebu cattle were examined for associations with trypanotolerance traits. One major histocompatibility complex encoded phenotype and two common leukocyte antigens gave indications of important associations. Planned research will further characterise the breed and define traits of importance to assist in increasing its productivity in Africa and thus in its conservation. The addition of a molecular genetics component to an integrated genetics research programme, principally through involvement in development of a linkage map of the bovine genome, will strengthen these efforts and make it possible to conserve specific N'Dama genes related to productivity.Key words: genetic resources, animals, trypanotolerance.
The management of rice genetic resources
Authors: Chang T. T.
Published: April 2011

Rice growers and researchers are endowed with an enormously rich germ plasm of pantropical distribution, mostly conserved before serious genetic erosion sets in. Efficient management of the conserved resources and effective use of the diverse gene pools justify arduous and costly investments in conservation. A sound conservation system requires adequate field space for seed increase and rejuvenation, cost-efficient and secure storage facilities, a database management system, availability of conserved materials and related information to users, and vigilant monitoring of seed viability. Linkage with evaluators, breeders, and biotechnologists is essential for full use of the conserved materials. Periodic consultation with specialists will extend a collection's usefulness, through further collection or re-collection of germ plasm and in situ conservation, compatibility of documentation systems, and enhanced interinstitutional and international collaboration. Training of germ-plasm workers should be part of the management system. The continuity in human resources will provide security, their dedication will ensure service, interdisciplinary communication will promote use. Improving the capability of national genebanks augments the security of collections preserved at duplicate sites. Gene-bank management must be sustained by adequate administrative and financial support. An effective public information program will further ensure support and security.Key words: rice, Oryza sativa, genetic resources, genetic conservation, gene-bank management.
Implications of the Hiroshima–Nagasaki genetic studies for the estimation of the human "doubling dose" of radiation
Authors: Neel J. V. , Schull W. J. , Awa A. A. , Satoh C. , Otake M. , Kato H. , Yoshimoto Y.
Published: April 2011

Since 1946 a continuous effort to evaluate the potential genetic effects of the atomic bombs has been sustained. Observations on children born in Hiroshima and Nagasaki include sex ratio, congenital malformations, stillbirths, survival of liveborn infants, chromosomal abnormalities (sex chromosomal abnormalities and balanced chromosomal rearrangements), mutations altering protein structure or activity, and physical growth and development. There are no statistically significant differences between the children of parents who received increased amounts of radiation at the time of the bombings and those whose parents did not. However, the difference between the two sets of children is consistent with the hypothesis of a genetic effect of the exposure, but its magnitude suggests humans are not as sensitive to the genetic effects of radiation as projected from the mouse paradigm.Key words: Hiroshima–Nagasaki, genetic doubling dose, radiation.
Development of genetic research in the USSR
Authors: Shumny V. K.
Published: April 2011

Two periods of the development of genetic research in the USSR with reference to its current trends of plant and animal genetics, cytogenetics, and molecular genetics are reviewed. A short list of priority areas is established: the maintenance and use of unique gene pools of plants and animals; the domestication of animals and cultivation of new plants; the development of programmes for mathematical treatment of genetic data banks. It is suggested to consider them within the framework of international projects. The idea is to promote the collaborative efforts of scientists on an international scale.Key words: genetics in the USSR, current trends, international cooperation.
Herbicide-tolerant mutants of corn
Authors: Anderson Paul C. , Georgeson Marcy
Published: April 2011

Eight imidazolinone herbicide resistant corn cell lines were obtained from in vitro cell culture selections. Plants were regenerated from five of the lines and resistant progeny obtained from four. Of the four, one line showed cross resistance to a sulfonylurea herbicide (class A), while three lines were resistant only to imidazolinones (class B). The class A line and one class B line were characterized in detail. Line XA17 possessed a single semidominant gene for resistance and plants homozygous for the trait showed 300-fold resistance to imazaquin and 100-fold resistance to chlorsulfuron. Resistance was due to decreased herbicide sensitivity of acetohydroxy acid synthase (AHAS), the common site of action of the imidazolinone and sulfonylurea herbicides. Resistance was stable following four to six backcrosses to corn inbred lines. Line QJ22 (class B) plants homozygous for tolerance showed 30-fold resistance to imazethapyr and no resistance to imazethapyr and no resistance to chlorsulfuron. The biochemical mechanism of resistance for line QJ22 is presently not clear.Key words: corn, maize, herbicide tolerance, acetohydroxy acid synthase, imidazolinone, sulfonylurea.
Biotechnology and the Third World: the missing link between research and applications
Authors: Zilinskas Raymond A.
Published: April 2011

A United Nations University study investigated the activities of four major United Nations agencies that focussed on helping developing countries gain advanced capabilities in biotechnology. Relevant program and project documents were scrutinized at agency headquarters and managers were interviewed. Then, projects underway in three case countries (Egypt, Thailand, and Venezuela) were examined. The resulting information was used to assess whether United Nations projects were fulfilling these countries' needs and (or) advancing their capabilities in biotechnology. The minute, United Nations originated assistance available was directed solely at increasing capabilities in research and thus benefited bioscientists and their institutes. However, as virtually no linkage exists between the research establishment and the industrial–marketing sector, results from indigenous research does not reach industrialists or health workers. Consequently, biotechnology is neither advancing economic development in the case countries nor helping solve national problems. This situation is likely to persist because corrective systemic changes will be difficult to implement. Major implications of these findings are discussed, particularly as they bear on the United Nations system.Key words: Third World biotechnology, capability building in biotechnology, United Nations assistance, Egypt, Thailand, Venezuela.
Aneuploids induced by deficiencies of chromosome 9 and analysis of the time of nondisjunction in cotton
Authors: Myles Jr. E. L. , Endrizzi J. E.
Published: April 2011

Plants of allotetraploid cotton, Gossypium hirsutum L. (2n = 4x = 52), which are monosomic for chromosome 9 or haplodeficient for the long arm of the chromosome, an Ah genome chromosome, produce a high frequency of aneuploid progeny. The aneuploids include monosomes, trisomes, and multiple monosomic and trisomic combinations that are the result of chromosome nondisjunction, which is induced by the deficiency of the long arm of chromosome 9. Loss of chromosomes occurs far more frequently than additions, and chromosomes of the Ah genome undergo nondisjunction at a significantly greater rate than do chromosomes of the Dh genome. Stained paraffin sections of ovules at different stages of development of monotelodisomic 9 and normal plants (TM1) were analyzed to determine the time and probable causes of nondisjunction during megasporogenesis. The most significant difference between mono 9 and TM1 was observed in ovules in stages of development just before and at the time of flowering. The mono 9 female gametophytes had supernumerary nuclei, indicating that chromosome nondisjunction occurs at the mitotic divisions of the embryo sac.Key words: chromosome nondisjunction, aneuploids, megasporogenesis, cotton, Gossypium hirsutum cytogenetics.
A genetic basis for variations in meiotic recombination in Petunia hybrida
Authors: Cornu A. , Farcy E. , Mousset C.
Published: April 2011

Experimental data show that the meiotic recombination rate during female gametogenesis is controlled by one major nuclear factor, symbolized by Rm1, i.e., recombination modulator 1. The existence of modifiers, suggested by several data, remains to be demonstrated. Rm1 has been located on chromosome II by linkage with locus lu1. The regulation exerted by Rm1 is not directed only to a particular chromosome, but is more general. The recombination rate increases considerably for pairs of closely linked genes on chromosomes I, II, V, VI, and VII; it remains unchanged for a pair of weakly linked genes on chromosomes IV and decreases for a pair of moderately linked genes on chromosome III. Rm1 affects recombination in both male and female gametogeneses, but the effects differ in the two. The marked regions on chromosome III and VII were equally affected in male and female meioses, but the marked regions on chromosome II and VI were unaffected in male meiosis.Key words: Petunia hybrida, recombination, meiosis.
Inheritance and linkage relationships of allozymes of eastern white cedar (Thuja occidentalis) in northwestern Ontario
Authors: Perry D. J. , Knowles P.
Published: April 2011

Allozyme variants of 12 enzyme systems were examined in seed tissues of eastern white cedar (Thuja occidentalis L.), using starch gel electrophoresis. Nine loci were polymorphic and deviation from a 1:1 segregation ratio was observed between two of three alleles at one locus (Mdh-1). Of the possible 36 locus-pair combinations, 23 could be tested for linkage. Significant linkage was detected for three pairs of loci (Aat-1/Mdh-1, Aat-1/Pgm, and Idh-2/Me). Trees jointly segregating for Aat-1 and Pgm fell into two classes, one with a low recombination frequency (9.1%) and the other with a higher recombination frequency (26.6%). An inversion polymorphism is a possible cause of this linkage heterogeneity observed among trees.Key words: allozymes, isozymes, inheritance, linkage, eastern white cedar, northern white cedar, Thuja occidentalis L., Cupressaceae.