bluuebunny/crossref_metadata_2025 huggingface dataset:
The inheritance of resistance to stem rust in 'K253', a hexaploid wheat with resistance from the tetraploid 'C.I. 7778'
Authors: Knott D. R.
Published: April 2011

The inheritance of stem rust (Puccinia graminis f. sp. tritici Eriks. and Henn.) resistance was studied in 'K253', a hexaploid wheat (Triticum aestivum L.) with resistance derived from a tetraploid wheat (T. turgidum L.). The studies indicated that 'K253' carries one dominant gene for good resistance to races 29 and 56 (probably Sr9e) and one recessive gene for moderate resistance to race 15B-1. In addition, some plants apparently carry a recessive gene for moderate resistance to race 56. Four different types of hexaploid near-isogenic lines were produced. One carried Sr9e and another the gene for moderate resistance to race 15B-1. Two carried genes that had not been identified in the genetic studies, including one that was apparently not derived from K253.Key words: stem rust resistance, Puccinia graminis tritici, wheat, Triticum aestivum, Triticum turgidum.
The effect of different Agropyron elongatum chromosomes on pairing in Agropyron – common wheat hybrids
Authors: Charpentier A. , Feldman M. , Cauderon Y.
Published: April 2011

Chromosome pairing at first meiotic metaphase was studied in hybrids between the common wheat cultivar Chinese Spring (CS) and an induced autotetraploid line derived from diploid Agropyron elongatum. The latter was found to carry genes for homoeologous pairing. To determine the chromosomal location of these and other genes that control pairing, disomic addition lines of A. elongatum in the cv. Chinese Spring were crossed with tetraploid cytotypes of A. elongatum, and pairing was then compared in the resulting hybrids and in hybrids between cv. Chinese Spring and tetraploid A. elongatum. The elongatum chromosomes were classified into those that suppress (6E), promote (5E, 3E, and possibly 1E), or have no effect on pairing (4E). The effect of chromosomes 2E and 7E was not studied. Chromosomes 5E and 3E differed in their effect on the degree and pattern of chromosome pairing. These findings are compared with the available data on the control of pairing in A. elongatum and in other Triticinae species.Key words: chromosome pairing, pairing promoter, Triticum, common wheat, Agropyron.
Mismatch repair and the fidelity of genetic recombination
Authors: Radman Miroslav
Published: April 2011

Two modes of mismatch repair are known to operate in bacteria: long-patch mismatch repair and very short patch mismatch repair. Very short patch mismatch repair systems act on a specific mismatch by conserving only one base pair. Therefore, when very short patch mismatch repair acts on heteroduplex recombination intermediates, it hyper-recombines specific markers by creating patchwork sequences, i.e., apparent multiple exchange events, on the repaired strand. Long-patch mismatch repair is antirecombinagenic, apparently by decomposing heteroduplex DNA or aborting its formation whenever well-recognized mismatches are formed by strand exchange between nonidentical parental sequences. It is postulated here that mismatch-stimulated antirecombination by long-patch mismatch repair is a "proofreading" system assuring high fidelity of homologous recombination. This accounts for chromosomal stability in eucaryotes (i.e., the rare occurrence of chromosomal aberrations and mitotic recombination versus the high frequency of precise sister chromatid exchange), suggests a role for diverged repetitive and other noncoding sequences as chromosomal antirecombination elements, and provides a molecular mechanism for speciation without the necessity of geographical separation.Key words: mismatch repair, genetic recombination, antirecombination, elements, speciation.
Genetic regulation of differentiation towards meiosis in the yeast Saccharomyces cerevisiae
Authors: Simchen Giora , Kassir Yona
Published: April 2011

Normally, meiosis and sporulation in Saccharomyces cerevisiae occur only in diploid strains and only when the cells are exposed to starvation conditions. Diploidy is determined by the mating-type system (the genes MAT, RME1, IME1), whereas the starvation signal is transmitted through the adenylate cyclase – protein kinase pathway (the genes CDC25, RAS2, CDC35 (CYR1), BCY1, TPK1, TPK2, TPK3). The two regulatory pathways converge at the gene IME1, which is a positive regulator of meiosis and whose early expression in sporulating cells correlates with the initiation of meiosis. Sites upstream (5′) of IME1 appear to mediate in the repression of the gene by repressors originating from both the mating-type and the cyclase – kinase pathways.Key words: sporulation, mating type, diploidy, adenylate cyclase, cAMP, protein kinase.
Advances in the genetics of reproductive isolation in Drosophila
Authors: Zouros E.
Published: April 2011

Speciation genetics is defined as the study of genetic events and processes that differentiate the probabilities that genetic material from individual members of a population will co-occur in individuals of some future generation. It follows that phenotypic attributes that contribute to this differentiation of probabilities (e.g., mating preferences, sterility, or infertility of individuals from certain types of matings) constitute the phenotype of speciation, and genetic loci that may affect these phenotypic attributes can be considered as speciation genes. The literature on genetic differences between hybridizable species of Drosophila that are responsible for morphological differences, mating preferences, hybrid inviability, and hybrid sterility are reviewed with special reference to the species pair D. mojavensis – D. arizonensis. The case for the involvement of karyotypic changes in speciation in rodents is briefly discussed. It is concluded that no major advance has been made in the speciation genetics of Drosophila since Dobzhansky initiated the field 40 years ago. Yet, the identification of several gene loci that cause hybrid inviability or sterility may open the way to the understanding of reproductive isolation at the molecular level. It is not clear whether this approach will lead to general molecular mechanisms underlying the speciation process.Key words: speciation genetics, hybrid sterility, reproductive isolation, Drosophila.
Y chromosomal fertility genes of Drosophila: a new type of eukaryotic genes
Authors: Hennig Wolfgang , Brand Reindert C. , Hackstein Johannes , Hochstenbach Ron , Kremer Hannie , Lankenau Dirk-Henner , Lankenau Susanne , Miedema Koos , Pötgens Andy
Published: April 2011

The Y chromosomal fertility genes of Drosophila are required for sperm differentiation. They are active only in primary spermatocytes where they form giant lampbrush loops. The molecular structure of these genes was investigated and revealed an unusual composition of DNA. Short, tandemly repeated sequence clusters are interrupted by longer and more heterogeneous sequences, which probably all represent transposable elements. No indication of the presence of protein-coding regions has been found within the fertility genes. However, the lampbrush loops bind site-specific proteins recognized by immunofluorescence techniques. This, together with other experimental data, led to the hypothesis that the Y chromosomal genes have a function in binding chromosomal proteins. The data and arguments in support of this gene model are summarized in this paper.Key words: Y chromosome, Drosophila, fertility genes, gene structure, lampbrush loops, spermatogenesis.
Mutational specificity and the influence of excision repair: insights into the mechanisms of error-avoidance and error-fixation
Authors: Glickman Barry W.
Published: April 2011

The excision repair process controlled by the uvrABC gene in Escherichia coli is the major pathway for the repair of a diverse series of DNA damages. To achieve a better understanding of the mechanics of this repair pathway and its impact upon mutagenesis, we have applied a recently developed technology by which the nature of mutation is determined at the DNA sequence level. A comparison of the classes and distribution of mutation in excision–repair-proficient and excision–repair-deficient strains of E. coli reveals that the absence of excision repair can alter both the nature of the mutations recovered as well as their distribution. This can occur in one of several ways. For example, under some circumstances the action of the UvrABC pathway can lead to interruptions of DNA strand continuity and an enhancement of both frameshift and deletion events. Such an effect is seen following damage by psoralen plus near UV (PUVA) treatment that produces cross-links in the DNA. In comparison, several other treatments produce similar distributions within the classes of mutations recovered but demonstrate an alteration in site specificity. Such is the case following UV irradiation. In this case, the data indicate that while the premutagenic lesions may be the same, mutation fixation in the presence and absence of excision repair may involve different mechanisms. Similarly, evidence from the repair of damage by ethylating agents indicates that while the nature of the mutations recovered is not altered, the preferred location of these events is altered in the absence of excision repair. These results indicate that local DNA sequence can affect on the efficiency of excision repair. The described studies demonstrate the potential use of mutational specificity studies to better understand the mechanisms of mutation fixation and mutation avoidance.Key words: mutational specificity, excision repair, alkylation, mutagenesis, UV, PUVA treatment, DNA sequence context effects, neighbouring base inferences.
125 years of experimental heat shock research: historical roots of a discipline
Authors: Nover Lutz
Published: April 2011

The history of experimental heat shock research over the last 125 years is briefly outlined. Starting with reports on the upper temperature limits of plant survival (1864) and on the spontaneous regression of skin cancer after a severe local inflammation (1866), studies on the heat shock response today are a major field of modern cell biology and include all types of prokaryotic and eukaryotic organisms.Key words: history, heat shock research.
Likelihood estimation of quantitative genetic parameters when selection occurs: models and problems
Authors: Gianola Daniel , Fernando Rohan L. , Im Sotan , Foulley Jean L.
Published: April 2011

Conceptual aspects of estimation of genetic components of variance and covariance under selection are discussed, with special attention to likelihood methods. Certain selection processes are described and alternative likelihoods that can be used for analysis are specified. There is a mathematical relationship between the likelihoods that permits comparing the relative amount of information contained in them. Theoretical arguments and evidence indicate that point inferences made from likelihood functions are not affected by some forms of selection.Key words: likelihood, quantitative genetics, parameters, selection.
Societal problems in human and medical genetics
Authors: Motulsky Arno G.
Published: April 2011

The applications of human and medical genetics raise many societal and ethical problems. This paper deals with a variety of such issues posed by current and future developments in genetic counseling, genetic screening, prenatal and predictive diagnosis, and gene therapy. The promise and problems of behavioral genetics are discussed. Problems of privacy, decision making, societal pressures, stigmatization, and informed consent to genetic study are raised. Use of genetic data by insurance companies or other public groups is discussed. The rapid unfolding of genetic information affecting human health and disease is producing difficult dilemmas. New problems are likely to surface, but human ingenuity and rationality is likely to find just and compassionate solutions in most settings.Key words: genetics and society; genetic diseases; counseling, genetic screening.
Eugenic sterilization: a preliminary comparison of the Scandinavian experience to that of Germany
Authors: Roll-Hansen Nils
Published: April 2011

The paper argues that historical analysis and explanation of eugenics in Germany can benefit much from systematic comparison to Scandinavia. Common cultural background and quite similar development up to 1933 provides a background for isolating salient causes in Nazi population policies. This comparison will also help a more precise understanding of the mutual dependence between science and politics in the case of eugenics. The author holds that many of the geneticists who participated in the eugenics debates of the 1930's and 1940's had a clearer grasp of the distinction between science and politics than most present day historiographers of eugenics.Key words: eugenics, sterilization, Scandinavia, Germany, geneticists.
The molecular manipulation of milk composition
Authors: Clark A. J. , Ali S. , Archibald A. L. , Bessos H. , Brown P. , Harris S. , McClenaghan M. , Prowse C. , Simons J. P. , Whitelaw C. B. A. , Wilmut I.
Published: April 2011

The introduction of cloned genes into the mouse germ line is now routine. Although more difficult technically, gene transfer has been accomplished in farm animals and offers the potential for genetic improvement. In this regard, we have been investigating the use of transgenic animals as production vehicles for high value proteins in milk. We have shown that DNA sequences derived from the gene encoding sheep β-lactoglobulin mediate efficient and specific expression in the mammary gland. A fusion gene comprising β-lactoglobulin sequences and those encoding antihemophilic human factor IX has been constructed. This construct has been introduced into sheep; it is expressed in the mammary gland, and the corresponding protein is secreted into milk.Key words: transgenic, mice, sheep, milk, proteins.
The effects of defective Suppressor-mutator insertions on the expression of a Bronze-1 allele in maize
Authors: Kim Hwa Yeong , Raboy Victor , Schiefelbein John W. , Nelson Oliver E.
Published: April 2011

Molecular and biochemical analyses of the maize transposable element mutant bronze-m13, which resulted from the insertion of a defective Suppressor-mutator element in an exon of a Bronze-1 allele, and of changes of state derived from bronze-m13 by internal deletions within the element have revealed how these mutant alleles condition a nonmutant phenotype in the absence of a trans-active Suppressor-mutator. The transposable element insertions are all in the same position, 38 base pairs 3′ to the single intron present in the bz locus. The insertions are transcribed with the gene, and the pre-mRNAs of bronze-m13 and CS1, CS5, CS6, and CS12 are then spliced using the intron donor splice site and either one of two acceptor splice sites in the defective Suppressor-mutator element. Only one of these two messages is translated to yield a functional enzyme. The pre-mRNA of CS9 is spliced only in the reaction that gives a translatable message since the pre-mRNA lacks the alternate acceptor splice site. The splicing reactions are detailed and related to the very different amounts of enzymatic activity produced by these alleles. The presence of an antisense message in CS12 plants to the defective Suppressor-mutator sequence transcribed with the bronze locus is also discussed.Key words: maize transposable element, Suppressor-mutator, splicing.
Genetics of allozyme variation in Cuphea lanceolata Ait.
Authors: Knapp S. J. , Tagliani L. A.
Published: April 2011

Genetic markers are needed for mating systems and breeding experiments in Cuphea lanceolata Ait.; however, none have been described in this species. Allozyme variation was analyzed among 14 F2 populations assayed for aconitase (ACO), diaphorase (DIA), esterase (EST), fluorescent esterase transaminase (FEST), glutamine oxaloacetate transaminase (GOT), menadione reductase (MNR), phosphoglucomutase (PGM), phosphoglucose isomerase (PGI), and shikimate dehydrogenase (SKDH) enzyme activity. At least 23 loci were resolved in these enzyme systems: 6 monomorphic loci, 5 poorly resolved loci, and 12 clearly resolved polymorphic loci. Observed segregation ratios were generally not significantly different (P > 0.05) from expected segregation ratios; however, segregation distortion was observed at Skdh-1 and Mnr-1 (Dia-1) in some F2 populations. Skdh-1 and Pgm-2 and Est-1, Est-2, Fest-1, and Mnr-1 comprise putative linkage groups. Allozyme variation was observed between and within accessions. The expected average heterozygosity was 16.3%. There were one to eight polymorphic loci among the F2 populations analyzed. There were an average of 2.05 alleles per locus. Several useful codominant markers were identified and a partial allozyme linkage map was constructed. Additional work is needed to revise and complete the map.Key words: Cuphea, isozymes, goodness of fit test statistics, lauric acid, capric acid.
Genome analysis of Thinopyrum caespitosum
Authors: Liu Zhi-Wu , Wang Richard R. -C.
Published: April 2011

Karyotype and meiotic analyses of the triploid hybrids Pseudoroegneria libanotica (Hackel) A. Löve (2n = 2x = 14; SS) × Thinopyrum caespitosum (C. Koch) R. R.-C. Wang (2n = 4x = 28) and T. bessarabicum (Saval &Rayss) A. Löve (2n = 2x = 14; JJ) × T. caespitosum (2n = 4x = 28) were performed to study the genomic constitution of T. caespitosum. Karyotype analysis of T. caespitosum was also carried out. In all karyotypic studies, the observed ratios between the longest and shortest chromosomes in the genome complements of the tetraploid species and triploid hybrids were higher than the hypothetical one based on the assumption that T. caespitosum has both Je and S genomes. This indicates that amphiplasty occurs at both the triploid and tetraploid levels. The hypothesis that T. caespitosum is an autotetraploid, either JJJJ (JJJeJe) or SSSS, is rejected. The meiotic data, 4.83 I + 0.78 rod II + 4.09 ring II + 2.14 III for P. libanotica × T. caespitosum and 5.16 I + 2.71 rod II + 2.16 ring II + 1.99 III for T. bessarabicum × T. caespitosum, support the hypotheses that the former has SSJe and the latter has JJeS as the genome formula. This evidence and that from other relevant hybrids strongly suggest that T. caespitosum is a true allotetraploid with the genome formula JeJeSS.Key words: karyotype, meiosis, phylogeny, amphiplasty, genome, Lophopyrum, Thinopyrum, Agropyron, Pseudoroegneria.
On the cytology of two species of Necrobia (Oliv.) (Coleoptera: Cleridae)
Authors: Yadav J. S. , Dange M. P.
Published: April 2011

The karyology of Necrobia ruficollis F. and Necrobia rufipes De Geer was investigated. The male karyotype of the species is 18♀:8+Xyp. Details of structure and behaviour of chromosomes during cell division are presented. Variations in the morphology of chromosomes in Necrobia species and trends in the evolution of karyotypes in the Cleridae are discussed.Key words: Cleridae, karyotype, sex chromosome mechanism, polyphaga, pericentric inversion.
Localized recombination nodules and sex chromosome behavior in the male mole cricket, Neocurtilla hexadactyla
Authors: Spyropoulos B. , Wise D. , Moens P. B.
Published: April 2011

During meiotic prophase, the 10 metacentric autosomal bivalents of the mole cricket, Neocurtilla hexadactyla Perty, formed synaptonemal complexes only at their ends. These complexes were of similar morphology to those of other species. Virtually all of these distal synaptonemal complex segments contained one or more recombination nodules. There was complete correlation between the locations of the synaptonemal complex segments at pachytene and chiasmata at diplotene. The sex chromosomal bivalent X2 and Y, formed a synaptonemal complex at one end only. While no apparent physical or spatial connection was found during prophase between the X2Y bivalent and the third sex chromosome, X1, electron-dense material covered the centromeres of X1 and Y and to a lesser extent X2, thus differentiating the centromeres of the sex chromosomes from those of the autosomes.Key words: localised pairing, recombination nodules, chiasmata, sex chromosomes.
Inheritance of somatic embryogenesis in alfalfa (Medicago sativa L.)
Authors: Hernández-Fernández M. M. , Christie B. R.
Published: April 2011

To study the inheritance of somatic embryogenesis in alfalfa (Medicago sativa L.), three alfalfa genotypes were self-pollinated and intercrossed. A70-34 is a highly embryogenic genotype; R3 produced callus but not embryos; and MK does not produce callus. Callus production was controlled by one locus with complete dominance. In a survey of 107 alfalfa genotypes, the dominant and recessive alleles were present in equal frequencies. Embryogenesis among those plants producing callus was controlled by two complementary loci with additivity within each locus. The suggested designations for the two genes are Rna and Rnb.Key words: alfalfa, Medicago sativa L., tissue culture, somatic embryogenesis, inheritance.
Voanioala gerardii has the highest known chromosome number in the monocotyledons
Authors: Johnson M. A. T. , Kenton A. Y. , Bennett M. D. , Brandham P. E.
Published: April 2011

A new monotypic genus from Madagascar, Voanioala gerardii, has at least 2n = 596 chromosomes, the highest number known in the monocotyledons and exceeded perhaps by only a single known dicotyledon count, namely Sedum suaveolens (2n = ca. 640). Two seedlings had 4C DNA amounts of 122.0 ± 5.6 and 117.4 ± 8.0 pg, respectively. Chromosome lagging was common in mitotic cells and probably results in somatic variation in chromosome number, but somatic polyploidy derived from endoreduplication was not detected.Key words: Voanioala, palm, new genus, high chromosome number, polyploidy, C-value.
Cytotaxonomic differentiation of Wilhelmia equina (Linné, 1747) and Wilhelmia lineata (Meigen, 1804) (Diptera: Simuliidae)
Authors: Weber E. Andreas , Grunewald Jörg
Published: April 2011

In most cases the larvae of Wilhelmia equina and W. lineata cannot be distinguished by using classical morphological features. The morphological characteristics of the salivary gland polytene chromosomes allow one to differentiate clearly between the two species. Characteristic for W. equina are the extended region between the centromere, Ctr (transformed centromere), and the nucleolus organizer, NO, in IS, the definitive position of RB (ring of Balbiani) and bulge in IIS, and the fan-shaped IIIL telomere. The chromosomes of W. lineata are marked by complex chromosomal polymorphisms, the altered position of RB and bulge on IIS and by a strong ectopic pairing of centromeres. The comparison of banding patterns provides several intraspecific polymorphic inversions and interspecific fixed rearrangements for species diagnosis. Partial chromosome maps were established. The comparison of the chromosomal banding pattern of Wilhelmia with that of the Simulium standard reveals a whole-arm interchange between chromosomes I and II in Wilhelmia identical with that in Metomphalus, Prosimulium vernale, a form of P. mixtum, and Metacnephia.Key words: cytotaxonomy, Simuliidae, Wilhelmia equina, Wilhelmia lineata, larvae.
Synaptonemal complex formation in rye (Secale cereale) heterozygous for telomeric C-bands
Authors: Gillies C. B. , Lukaszewski A. J.
Published: April 2011

Zygotene–pachytene nuclei from a rye line heterozygous for most terminal C-bands were found by electron microscopic spreading analysis to have unequal lateral elements at most synaptonemal complex telomeres. An unpaired lateral element protruded beyond the end of the synaptonemal complex at each such telomere. Another rye line with only one C-band heterozygous telomere had only one uneven synaptonemal complex telomere. The length differences between paired lateral elements in heterozygotes (both total complement and individual synaptonemal complexes) was considerably less than the difference in DNA content or somatic metaphase chromosome size between C-band positive and C-band negative lines. There was no evidence of a synaptic adjustment effect reducing the telomere length differences in later pachytene–diplotene stage nuclei. Heterozygosity for the 1RL terminal C-band resulted in a slight reduction in chiasma frequency in that arm but no shift in chiasma position.Key words: rye, C-bands, telomeres, chromosome pairing, synaptonemal complex.
Comparison between synaptonemal complexes at pachytene and chromosome association at metaphase I in heterozygotes for a "nonreciprocal" translocation of rye
Authors: Naranjo T. , Roca A. , Goicoechea P. G. , Jong J. H. de , Smilde W. D.
Published: April 2011

A comparative analysis of synaptonemal complex formation at pachytene and chromosome association at metaphase I was carried out in heterozygotes for translocation T242W (2R/6R) of rye (Secale cereale L.). Synaptonemal complex formation supported earlier light microscopic observations that one exchanged segment of this translocation was very small and restricted to the telomere or had been lost. Negative interference between the interstitial segments with respect to chiasma formation was detected at metaphase I. This interference was apparently the result of the simultaneous occurrence of either asynapsis or nonhomologous pairing around the translocation point at pachytene. Negative interference detected across the centromere of 6R was attributed to nonhomologous pairing. The presence of an intercalary C-band in the interstitial segment 2RLi or in the 1RS arm had no apparent influence on synaptonemal complex formation. Unmatched ends of synaptonemal complex 1R and of the multivalent were in most cases associated with heterozygosity for the telomeric C-heterochromatin.Key words: Secale cereale, translocation, synapsis, interference, C-banding.
Somatic chromosome karyotype of tomato based on in situ hybridization of the TGRI satellite repeat
Authors: Lapitan Nora L. V. , Ganal Martin W. , Tanksley Steven D.
Published: April 2011

A karyotype of tomato mitotic chromosomes was constructed based on in situ hybridization to a 162-bp telomeric DNA repeat, TGRI. Variation in the spatial and quantitative distribution of this repeat creates distinct patterns for most of the chromosomes, which along with other morphological characteristics (i.e., length and arm length ratio), allow the identification of each of the 12 mitotic chromosomes of tomato. The structure and physical size of the TGRI clusters were further investigated by means of pulsed-field gel electrophoresis. Approximately 30 hybridizing fragments were observed in the range of 25 to 1000 kb when high molecular weight DNA was digested with BglII and probed with TGRI. The total molecular weight of these fragments is approximately 14 million bp, which is close to the estimated total length of TGRI in the genome (12.5 million bp) based on genomic reconstruction experiments. The results suggest that most of the TGRI clusters consist of single, uninterrupted blocks of satellite DNA. Assignment of somatic chromosomes, identified by TGRI hybridization to the previously established tomato linkage groups, was accomplished via in situ hybridization to mitotic spreads of primary trisomic lines. Using this information, we estimate the somatic length and DNA content of each of the tomato chromosomes and chromosome arms. Key words: Lycopersicon esculentum, somatic karyotype, in situ hybridization, satellite DNA, pulsed-field gel electrophoresis.
Phylogenetic relationships of Triticum tauschii, the D-genome donor to hexaploid wheat. 4. Variation and chromosomal location of 5S DNA
Authors: Lagudah E. S. , Clarke B. C. , Appels R.
Published: April 2011

The 5S DNA sequences in Triticum tauschii are organised in large clusters containing units that are primarily either 420 ("short") or 490 base pairs (bp) in length ("long"). The main cluster of short units was shown to be located on chromosome 1D in hexaploid wheat and is designated 5SDna-Dl, while the cluster of long units was shown to be on chromosome 5D and is designated 5SDna-D2. The chromosomal locations in hexaploid wheat most likely correspond to those in T. tauschii and this could be shown directly for the 5SDna-D2 locus by using a T. tauschii 5D substitution in 'Chinese Spring' wheat. The sequence alignment of units derived from 5SDna-D1 and 5SDna-D2 revealed three apparent deletions in the noncoding spacer region, which were fixed in units from 5SDna-D1, and one deletion, which was fixed in units from 5SDna-D2. A minor size class, 400 bp long and closely related to the units from 5SDna-D1, was found in 2 of 415 accessions surveyed. A continuous range of quantitative changes in the number of 5S DNA units at the two loci was evident with up to a 10-fold relative abundance level of units being found in some accessions. Triticum tauschii var. typica was particularly noteworthy in that many accessions showed more units at 5SDna-D2 relative to 5SDna-D1. Partial thermal dissociation experiments with radioactive probes, synthesized from either the short or long 5S DNA units, hybridized to genomic DNA showed that the population of units at the respective loci were relatively homogeneous and clearly distinct from each other. In addition, these experiments further established the close phylogenetic relationship between T. tauschii and the D genome of wheat.Key words: Triticum tauschii, 5S DNA, sequence variation, chromosomal location.
Chromosomal location in common wheat of a gene (Cmcl) from Aegilops squarrosa that conditions resistance to colonization by the wheat curl mite
Authors: Whelan E. D. P. , Thomas J. B.
Published: April 2011

Wheat streak mosaic is a destructive disease of wheat caused by wheat streak mosaic virus. Wheat streak mosaic virus is vectored by the wheat curl mite (Eriophyes tulipae Keifer). A single dominant gene conditioning resistance to colonization by the mite vector was transferred from Aegilops squarrosa L. to a synthetic amphiploid (AC PGR 16635) and then to common wheat (Triticum aestivum L. em. Thell.) through backcrossing. Because of its origin, the transferred gene was probably located in the D genome. Monosomics 1D through 7D were crossed with a homozygous resistant line with the pedigree Norstar*4/AC PGR 16635. Both 41- and 42-chromosome F1 plants were identified and selfed to obtain F2 seed. The observed proportion of resistant and susceptible plants in 6 of the 7 F2 families from monosomics, and in all 7 of the F2s from disomics, did not deviate significantly from a 3:1 ratio. However, the proportion of resistant plants from the F2 of monosomic 6D was significantly (p < 0.01) in excess of this ratio and susceptible plants from this family were nullisomic for all or part of 6D. In crosses with standard ditelosomic stocks, telocentrics from a ditelosomic derivative of susceptible individual of this F2 paired with 6D(L) but failed to pair with 6D(S). The F2 of heterozygous resistant plants that were monotelodisomic for the long arm of 6D(L) segregated approximately 19 resistant to 1 susceptible, while those from monotelodisomics for the short arm segregated normally (3 resistant to 1 susceptible, p = 0.27). These data show that the gene Cmcl for mite resistance is located on the short arm of chromosome 6D. Key words: Aegilops squarrosa, wheat streak mosaic virus.
Structure of chromosome 5A of wheat speltoid mutants induced by the gametocidal genes of Aegilops speltoides
Authors: Tsujimoto H. , Noda K.
Published: April 2011

Speltoid spikes occur when the dose of Q, (suppressor of speltoidy) located on the long (q) arm of chromosome 5A, decreases from the normal two to one or none. In crossed or selfed progeny of wheat lines that carry the gametocidal genes, Gc1a or Gc1b, 35 speltoid mutants appeared independently. The nature of the mutants, whether due to gene mutation or due to chromosome deletion, including the Q gene, was investigated. The mutants in the M1 generation were self-pollinated and segregation of the character in the M2 was observed. Speltoid plants in the M2 were crossed with ditelosomic 5AL (20II + tII), and pairing between the telosome 5AL and the chromosome that caused speltoidy was observed. Of the 25 lines that were analyzed by the two methods, 22 had a chromosome deletion on the long arm of chromosome 5A, the length of which was variable. The chromosome with deletion could be classified into at least three groups by comparison with the length of telo-univalent 5AL. In the M3 generation, six homozygous deletion lines were selected. Chromosome breakage that resulted in the deletions could be due to the involvement of a transposable element or a restriction – modification system.Key words: Triticum aestivum, Aegilops speltoides, gametocidal gene, chromosome breakage, mutation.
Polymorphism in ribosomal DNA repeat units of 12 Hordeum species
Authors: Molnar Stephen J. , Fedak George
Published: April 2011

Total genomic DNA was isolated from leaves of individual accessions of 12 Hordeum species. SacI, HindIII, and BamHI restriction fragments hybridizing to the wheat rDNA probe pTA71 were compared. Thirteen rDNA repeat unit length variants were recovered, which combined to produce 11 distinct phenotypes. All rDNA repeat units had two SacI sites and no HindIII sites. The rDNA repeat units of H. secalinum, H. hrasdanicum, and H. distichum all had 3 BamHI sites, but in different configurations. The rDNA repeat units of the other species had at least 4 BamHI sites. Ladders of small hybridizing fragments in 8 of 9 of the latter accessions indicated the presence of occasional BamHI sites in some subrepeats within the intergenic spacer regions of the rDNA repeat units. Different distributions of BamHI restriction site maps within the Hordeum sections strengthen the concept of using variation in rDNA restriction sites as a taxonomic character.Key words: Hordeum, ribosomal DNA, polymorphism.
Enhanced seed set and crossover frequency in regenerated potato plants following anther and callus culture
Authors: Singsit C. , Veilleux R. E. , Sterrett S. B.
Published: April 2011

Twenty somaclones regenerated from a 2n pollen producing clone of diploid Solanum phureja and its anther-derived heterozygous diploid regenerant were found to vary for several morphological traits. However, after selection for fertility and diploidy, 4 of the 20 somaclones were not significantly different among themselves or from the original clone. When used as pollen parents in 4x–2x crosses to Solanum tuberosum cv. Atlantic, all the four somaclones exhibited higher seed set in comparison with the original clone. Progeny analysis revealed that 2 of the 4 exhibited higher recombination frequency between the centromere and the y gene. The estimated increased map distance of the y locus ranged from 3.4 to 10.0 units. Hybrid progeny analysis revealed no significant differences among 4x–2x and only a single difference among 2x–2x hybrid families for several morphological characters. Seed set and recombination data suggest that variation induced in tissue culture may have occurred without detectable morphological change. Assuming no adverse tissue culture effects, breakage of tight linkage between desirable and undesirable characters may be facilitated by shoot regeneration from callus before backcrossing.Key words: Solanum phureja, gene–centromere mapping, callus culture, recombination frequency, 4x–2x crosses.
Involvement of Coprinus endonuclease in preparing substrate for in vitro recombination
Authors: Montgomery G. P. , Lu B. C.
Published: April 2011

A functional recombination assay involving the tetracycline mutant plasmids, pUW1 and pUW4, was used to assess (i) the nature of the DNA substrates needed and (ii) the involvement of Coprinus endonuclease in preparing substrate, for the RecA-directed recombination process. A gapped circular plasmid and a linear or a nicked circular plasmid are efficient substrate combinations in this system to achieve a 160-fold increase in the in vitro recombination frequency over the control levels. The Coprinus endonuclease obtained from early meiotic prophase can produce such substrates. The recombination frequency obtained with the combination of gapped pUW1 plasmids initially relaxed by the Coprinus endonuclease and linear pUW4 plasmids produced by the site-specific BamHI digest is 10-fold lower than that obtained when both substrates are digested by BamHI. The results suggest that the Coprinus endonuclease creates random nicks on plasmid DNA. Glyoxal gel electrophoretic analysis was used to confirm this random nicking activity of Coprinus endonuclease.Key words: Coprinus, genetic recombination, endonuclease, recA.
Variable conservation of nucleolus organizer regions during karyotypic evolution in Microtidae
Authors: Sánchez A. , Burgos M. , Jiménez R. , Guardia R. Díaz de la
Published: April 2011

The location of the nucleolus organizer regions (NORs) was studied in four species of Microtidae (Microtus nivalis, M. cabrerae, M. arvalis, and Arvicola sapidus). The comparative study of these locations shows that some NORs have been conserved despite the chromosome rearrangements that have occurred through karyotypic evolution, while others have been lost. In addition, there are many chromosomes in which NORs seem to have appeared or been lost without apparent relation to the chromosome rearrangements. Some hypotheses regarding these facts are discussed in the text.Key words: nucleolus organizer regions, Microtidae, karyotypic evolution.
Inversion polymorphism in Indian natural populations of Drosophila melonogaster
Authors: Singh B. N. , Das Aparup
Published: April 2011

Six natural populations (three urban and three rural) of Drosophila melonogaster from India were analysed for chromosome inversions, revealing the presence of 19 different paracentric autosomal inversions. One new inversion has also been detected in a laboratory stock established from flies collected from Kerala. In total 20 different paracentric inversions in Indian D. melonogaster have been detected during the present study, and of these, 4 are common cosmopolitans; 2 are rare cosmopolitans; 7 are recurrent endemics; and 7 are unique endemics. The quantitative data clearly show that the urban populations are different from the rural ones with respect to inversion polymorphism.Key words: inversion polymorphism, Indian natural populations, Drosophila melonogaster.
Identifying a single-copy DNA sequence associated with the expression of a heterochromatic gene, the light locus of Drosophila melanogaster
Authors: Devlin Robert H. , Holm David G. , Morin Karen R. , Honda Barry M.
Published: April 2011

Although little is known about the molecular organization of most genes within heterochromatin, the unusual properties of these chromosomal regions suggest that genes therein may be organized and expressed very differently from those in euchromatin. We report here the cloning, by P transposon tagging, of sequences associated with the expression of the light locus, an essential gene found in the heterochromatin of chromosome 2 of Drosophila melanogaster. We conclude that this DNA is either a segment of the light locus, or a closely linked, heterochromatic sequence affecting its expression. While other functional DNA sequences previously described in heterochromatin have been repetitive, light gene function may be associated, at least in part, with single-copy DNA. This conclusion is based upon analysis of DNA from mutations and reversions induced by P transposable elements. The cloned region is unusual in that this single-copy DNA is embedded within middle-repetitive sequences. The in situ hybridization experiments also show that, unlike most other sequences in heterochromatin, this light-associated DNA evidently replicates in polytene chromosomes, but its diffuse hybridization signal may suggest an unusual chromosomal organization.Key words: polytene chromosomes, P transposon, in situ hybridization, middle-repetitive DNA.
Inheritance and distribution of variation at four avenin loci in North American oat germ plasm
Authors: Souza E. , Sorrells M. E.
Published: April 2011

Avenins (prolamines of the Avena genus) have been shown to be useful in taxonomic studies and cultivar identification; specific allelic identification could assist in these types of studies as well as providing a basis for future linkage and gene mapping studies. The avenin patterns produced by nondenaturing polyacrylamide gel electrophoresis were compared in 70 North American oat cultivars and germ plasms. Populations of F2 progeny were subsequently evaluated to test for allelism of proteins found to be noncoincident in the survey of homozygous cultivars. A minimum of four loci (Av1, Av2, Av3, and Av4) were found to possess alternate alleles with distinctive electrophoretic mobilities. Segregation of 10 alternate alleles were observed in studies of F2 progeny: four for Av1, and two each for the other three loci. Additional variation found among the surveyed cultivars suggested at least two additional electrophoretically variant polypeptides. Several of the alleles were found to be associated with cultivars from specific geographic regions. Two examples were (i) the near exclusive association of the Av10.76 allele with Canadian cultivars and (ii) the high association of the Av10.58 allele with fall-planted cultivars. Fifty percent (SE ± 10.7%) of the fall-planted cultivars have the Av40.58 allele compared with 27.1% (SE ± 8.8%) of spring-planted cultivars.Key words: avenins, prolamines, polyacrylamide gel electrophoresis, linkage.
Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). III. G-banding analysis of Petrogale inornata and P. penicillata
Authors: Eldridge M. D. B. , Close R. L. , Johnston P. G.
Published: April 2011

The karyotypes of Petrogale inornata and the two currently recognised races of Petrogale penicillata were examined using G-banding from cultured fibroblasts. Petrogale inornata (2n = 22) was found to retain plesiomorphic chromosomes 3 and 4 but possessed an apomorphic inverted chromosome 5 (5i). This 5i appears identical with the 5i found in two other Queensland taxa, Petrogale assimilis and Petrogale godmani, and can be derived from the ancestral chromosome 5 by an extensive paracentric inversion or a centromeric transposition. Petrogale penicillata penicillata (2n = 22) and Petrogale penicillata herberti (2n = 22) both possess the synapomorphic acrocentric chromosome 3, which appears to differ from the plesiomorphic 3 by a small centromeric transposition. Petrogale p. penicillata was also found to be characterised by an apomorphic acrocentric chromosome 4, while P. p. herberti was characterised by an autapomorphic submetacentric chromosome 4. Both apomorphic chromosomes 4 can be related to the plesiomorphic chromosome 4 by centromeric transpositions. Thus although P. inornata is chromosomally distinct it is more closely related to other north Queensland taxa than it is to either P. p. penicillata or P. p. herberti.Key words: chromosomal rearrangements, G-banding, Marsupialia, Petrogale, Macropodidae.
A partial map of the barley genome incorporating restriction fragment length polymorphism, polymerase chain reaction, isozyme, and morphological marker loci
Authors: Shin J. S. , Chao S. , Corpuz L. , Blake Tom
Published: April 2011

Nine low copy number genomic DNA clones, a ribosomal sequence, and seven cDNA clones were found to identify polymorphisms in cultivated barley (Hordeum vulgare L.). An F2 population consisting of 100 plants was produced from a cross between a high-yielding two-rowed feed barley cultivar and a genetic marker stock homozygous for nine recessive and one dominant morphological marker genes. Through the use of these 10 well-distributed marker genes, five previously mapped isozyme loci, and two storage-protein loci, the approximate recombinational location for each of 17 restriction fragment length polymorphism loci was estimated. One clone, pMSU21, identified variation that appeared to be the result of a small insertion–deletion event that differentiated two-rowed and six-rowed genotypes. This difference was characterized, and one allele was sequenced. Oligonucleotide primers that flanked the insertion–deletion event were synthesized, and DNA samples from the F2 population were subjected to polymerase chain reaction sequence amplification. The variation identified by this technique was determined to be allelic to the variation identified using pMSU21 in Southern blot analysis. Maps of previously undescribed informative clones are included.Key words: Hordeum vulgare, restriction fragment length polymorphisms, genetic linkage map, polymerase chain reaction.
Aberrant splicing of a naturally occurring alcohol dehydrogenase null activity allele in Drosophila melanogaster
Authors: Freeth Allan L. , Gibson John B. , Wilks Ann Verona
Published: April 2011

The DNA sequence of a naturally occurring alcohol dehydrogenase null activity allele, AdhnAC14, has eight extra nucleotides (in two groups of four) in the second intron, commencing six bases 3′ from the 5′ splice site. A stop codon was also found in exon 2. S1 nuclease protection experiments have shown that the insertions in intron 2 disrupt the correct splicing of intron 2. The null allele produces a transcript approximately 100 bases longer than the normal mature adult transcript, and the amount of the null allele transcript is only about 10% of the normal level.Key words: alcohol dehydrogenase, null allele, splicing, S1 nuclease, Drosophila melanogaster.
Linkage relations of Gli-D1, Rg2, and Lr21 on the short arm of chromosome 1D in wheat
Authors: Jones S. S. , Dvořák J. , Qualset C. O.
Published: April 2011

Homozygous recombinant substitution lines, derived from a cross of Triticum aestivum 'Chinese Spring' with a disomic substitution line of Triticum tauschii chromosome 1D in 'Chinese Spring', were used to investigate the linkage relationships among the loci Glu-D1, encoding high molecular weight glutenin storage proteins, Gli-D1, encoding gliadin storage proteins, Rg2, controlling glume color, and Lr21, conferring leaf-rust resistance. Gli-D1, on chromosome arm 1DS, is tightly linked to Rg2 and Lr21 (1.4 and 5.6% recombination, respectively). The order of the loci is Gli-D1–Rg2–Lr21. Glu-D1, on chromosome arm 1DL, segregates independently (P = 0.43) of Gli-D1, Rg2, and Lr21. The position of Glu-D1, Gli-D1, Rg2, and Lr21 in the genetic linkage map of chromosome 1D agrees with the position of storage protein, glume color, and rust-resistance loci on chromosomes 1A and 1B.Key words: leaf-rust resistance, seed storage protein, glutenin, gliadin, glume color, Triticum aestivum, Triticum tauschii.
An XXY sex chromosome anomaly in the mouse
Authors: Endo A. , Watanabe T. , Fujita T.
Published: April 2011

A cryptorchid male mouse with 41,XXY chromosome constitution was found in 300 male offspring that were born to our XO mice breeding colony. This individual had small testes with no sign of spermatogenesis at autopsy at 10 months of age.Key words: 41,XXY, mouse, XO mice colony, testes, spermatogenesis.
Characterization of genomes of timothy (Phleum pratense L.). I. Karyotypes and C-banding patterns in cultivated timothy and two wild relatives
Authors: Cai Q. , Bullen M. R.
Published: April 2011

In an attempt to know the phylogeny of timothy (Phleum pratense), the cultivated species and two wild relatives, Phleum alpinum and Phleum bertolonii, were karyotyped with conventional and Giemsa C-banding methods. In the hexaploid P. pratense (2n = 6x = 42), two sets of seven chromosomes were indistinguishable from each other both in morphology and in banding patterns and the third set of seven was found to be differentiated from them. Two genomes, A and B, were tentatively established. The banded karyotype in diploid P. alpinum (2n = 2x = 14) was close to the A genome, which was tetraploid in P. pratense, and the karyotype in P. bertolonii (2n = 2x = 14) was analogous to the B genome in P. pratense, which suggests these species were the genome donors of P. pratense.Key words: chromosome, genome, allopolyploid, Giemsa C-banding.