bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic analysis of a population of Tribolium. IX. Maximization of population size and the concept of a stochastic equilibrium
Authors: Desharnais Robert A. , Dennis Brian , Costantino Robert F.
Published: April 2011

Motivated by the genetic hypothesis that natural selection results in the maximization of the equilibrium population size, we quantified this latter equilibrium for laboratory populations of the flour beetle Tribolium castaneum, using the gamma probability density function. Gamma density functions were fitted to adult numbers for each of the experimental treatments that were started with frequencies of the corn oil sensitive (cos) allele in the range 0–1 at intervals of 0.1. The gamma density function adequately described all observed distributions. However, contrary to theory, statistical comparisons of the fitted distribution indicate that the polymorphic populations did not converge to the same identical distribution and that the polymorphic populations are intermediate in population size to the two homozygous groups. The need for a stochastic theory that combines both population size and genetic selection is discussed.Key words: natural selection, Tribolium, gamma distribution, maximum population size, stationary distribution, stochastic differential equation, stochastic population model.
Branched chain amino acid regulation of the ILV2 locus in Saccharomyces cerevisiae
Authors: Xiao Wei , Rank Gerald H.
Published: April 2011

Mutant regulatory loci of the branched pathway for the biosynthesis of isoleucine–valine and leucine were identified with the unusual phenotype of an amino acid dependent auxotrophy. Two mutant loci, bcs1 and bcs2, conferred branched chain amino acid sensitivity and showed independent segregation. Linkage studies defined bcs1 as a cis-acting regulatory site of ILV2 (SMR1). ILV2 upstream deletion analyses and high-copy transformation of the positive regulatory locus LEU3 ruled out the possibility of LEU3 protein binding palindromes mediating the branched chain amino acid dependent auxotrophy. In the presence of leucine and valine, the general amino acid control system (GCN4) was epistatic to bcs1 and bcs2, and under nonstarvation conditions GCN4 strains showed an increased acetolactate synthase activity over gcn4 strains. Thus in addition to general regulation of ILV2, GCN4 functions in basal level expression when the locus is subject to specific repression by pathway end product.Key words: yeast, isoleucine, leucine, valine pathway, amino acid sensitivity, gene regulation, multiple control.
Genome elimination in diploid and triploid Rana esculenta males: cytological evidence from DNA flow cytometry
Authors: Vinogradov A. E. , Borkin L. J. , Günther R. , Rosanov J. M.
Published: April 2011

Cytological aspects of hemiclonal (meroclonal) inheritance in diploid and triploid males of the hybridogenetic frog Rana esculenta (Rana ridibunda × Rana lessonae) have been studied by DNA flow cytometry. The fact that the R. ridibunda genome contains 16% more DNA than the R. lessonae genome provides the ability to discern cells containing genomes of any species from the water-frog complex under study. Data are presented showing that elimination of the R. ridibunda genome occurs in hybridogenetic males from certain populations. In triploid males, the cytogenetic mechanism of hemiclonal inheritance is simpler than in diploids: after the elimination of a genome (always the genome in the minority in the triploid set; "homogenizing elimination"), no compensatory duplication of the remaining genetic material is necessary, as it is in diploids. The process of elimination can be visualized in triploid males by using DNA flow cytometry to identify cells in the special phase of the spermatogonial cell cycle that we termed the E phase.Key words: Rana esculenta, genome elimination, non-Mendelian inheritance, spermatogenesis, DNA flow cytometry.
New Secale cereale (rye) DNA derivatives for the detection of rye chromosome segments in wheat
Authors: McIntyre C. L. , Pereira S. , Moran L. B. , Appels R.
Published: April 2011

Subcloning of a clone of the 120-bp family of rye, pSc119, has produced two extremely useful probes. pSc119.1 assays rye-specific dispersed repetitive sequence families. It is present on all seven rye chromosomes and hybridizes to the entire length of each chromosome, with the exception of some telomeres and the nucleolar organiser region. pSc119.2, in contrast, hybridizes predominantly to the telomeric regions of rye chromosomes, with some interstitial sites. Unlike pSc119.1, it assays similar repetitive sequence families in both wheat and rye chromosomes.Key words: Secale cereale, rye DNA probes, rye chromosome detection.
The macrosatellites of the Toulouse goose: the major tandemly repetitive DNA in the Toulouse goose genome
Authors: Zhu X. , Skinner J. , Burgoyne L. A.
Published: April 2011

This paper examines the principal classes of repetitive DNA of the Toulouse goose (Anser anser) genome. There are four major classes and they are tandem repeats of less than 200 base pairs (bp). The longest repeat (class A) is 190 bp long and starts with a HinfI site. Class B is 43 bp long, commencing with a FokI site. Classes A and B show no extensive homology to DNA sequences held on a current data base (Genbank) but were confirmed to exist as major repeats in another strain of goose, the Emden goose (Anser anser) genome. Classes C and D are 5-bp repeats of 5′ GAGAG 3′ and 5′ GGGAA 3′, respectively. The macrosatellites C and D were compared with a current data base (Genbank) and were found to exist in a variety of other organisms as satellites.Key words: anseriform, avian, goose, repetitive DNA.
Ribosomal RNA genes in diploid and amphidiploid Brassica and related species: organization, polymorphism, and evolution
Authors: Delseny M. , McGrath J. M. , This P. , Chevre A. M. , Quiros C. F.
Published: April 2011

Restriction maps for rRNA genes of the three cultivated diploid species Brassica nigra, B. oleracea, and B. campestris are described using the rDNA map of radish as a standard. rDNA subunit heterogeneity similar to that found in radish was observed in the Brassica species, thus resulting in complex hybridization patterns. Brassica campestris could be distinguished from the other two Brassica diploids by the absence of the EcoRI site E3 in the rDNA subunits in almost all the accessions tested, and by its smaller external intergenic spacer. Two radish probes covering specific regions of the rDNA subunit as well as two other heterologous probes permitted the assignment of specific fragments to coding and intergenic spacer regions. Amphidiploid species B. napus and B. juncea had rDNA profiles reflecting the combination of EcoRI fragments observed in their parental species. A series of alien addition lines disclosed rDNA regions on two chromosomes in the B. oleracea genome, distinguished by syntenic associations to other markers and by specific intergenic spacer fragment.Key words: rDNA, polyploidy, cole crops, Cruciferae, alien addition lines.
Identification of translocations in pea by in situ hybridization with chromosome-specific DNA probes
Authors: Simpson Paul R. , Newman Mari-Anne , Davies D. Roy , Ellis T. H. Noel , Matthews Peter M. , Lee David
Published: April 2011

Biotin-labelled DNA probes for tandemly repeated sequences have been used in in situ hybridization experiments as chromosome-specific markers in pea. Six of the seven chromosome pairs can be marked at single sites in this way. Translocations from a standard karyotype are revealed as chromosomes that have two hybridization sites, rather than one. By probing a tester set of reciprocal translocation (or interchange) lines, some of the markers can be assigned to chromosomes. The method is rapid and simple and, in the absence of well-resolved chromosome bands, provides a means for clarifying some of the problems in pea cytology.Key words: in situ hybridization, translocations, chromosome markers.
Variation among the dispersed (GATA)n sequences in Drosophila melanogaster
Authors: Simpson Paul R.
Published: April 2011

Five nonallelic copies of the dispersed (GATA)n repeated sequence of Drosophila melanogaster (referred to as GATA elements) have been sequenced and analysed. The GATA elements range in size from 111 to 444 bp, consisting predominantly of tandemly repeated GATAs, interspersed with variants of the subunit. The types and distributions of these variants are consistent with the hypothesis that they have arisen by a random accumulation of point mutations (substitutions, deletions, and insertions) in pure (GATA)n sequences. Duplications or deletions of the GATA subunit, and of GATA variants, have also probably occurred, as a result of either unequal crossing-over or slipped-strand mispairing. Evidence for duplication (deletion) has been obtained from a comparison of two allelic GATA elements isolated from different populations. GATA elements, in common with other dispersed, simple repeats, are probably highly variable in length.Key words: simple sequences, GATA element, Drosophila.
Genome size in parental and hybrid species of Bacillus (Insecta, Phasmatodea) from southeastern Sicily: a flow cytometric analysis
Authors: Marescalchi O. , Scali V. , Zuccotti M.
Published: April 2011

In Sicily five Bacillus taxa are found: two bisexuals, B. grandii (2n = 34, female; 2n = 33, male) and B. rossius (2n = 36, female; 2n = 35, male), and three thelytokous, B. atticus (2n = 34), B. whitei (2n = 35), and B. lynceorum (3n = 52). Their cytofluorometric 2C DNA values, in picograms, in order are 5.22 (♀) –4.31 (♂); 4.33 (♀) –3.89 (♂); 4.40; 4.53; and 6.80. These values represent the first flow cytofluorometric data on phasmatodean genome size. The highest value of B. grandii and the lowest one of B. rossius appear to be related to abundance and scarcity of C-heterochromatin, respectively, which is also rather low in B. atticus. The genome size of B. whitei agrees perfectly with its shown hybrid derivation from B. grandii and B. rossius. On the other hand the value of B. lynceorum is significantly lower than the one expected (7.38 pg) on the basis of its formerly suggested hybrid origin from the backcross B. whitei × B. grandii, but it appears much closer to, and not significantly different from, the value of 6.97 pg expected according to the newly suggested double allotriploid origin, mainly based on electrophoretic evidence, from B. atticus, B. rossius, and B. grandii. Finally, as far as Bacillus taxa are concerned, average stick-insect genome size appears to be just lower than that of other orthopteroid insects, and much lower (10 times) than that of the leaf insect Extatosoma tiaratum, obtained through static cytometry on Feulgen-stained DNA squashes.Key words: cytotaxonomy, DNA amount, hybrid speciation, parthenogenesis, stick insects.
Spontaneous somatic transfer of a segment from a wheat addition chromosome into the rye genome
Authors: Melz G. , Thiele V.
Published: April 2011

Wheat chromosome 3B when added to the rye genome causes resistance to powdery mildew of rye (Erysiphe graminis DC. f.sp. secalis Marchal) as the result of the action of the gene Rpm1. Wheat chromosome 3B also carries the gene Got-B3 for glutamate oxaloacetate transaminase. In two independent, vegetatively reproduced additions of 3B to rye, the extra wheat chromosome appeared to have been lost spontaneously, but both genes were still present. The rye chromosome into which the genes had been transferred could not be identified. Chromosome 3R appeared to be morphologically unchanged, no telomeric heterochromatin normally present in any rye chromosome had disappeared, and no wheat B-genome centromeric heterochromatin was observed. At meiosis the chiasma frequency was reduced, resulting in the frequent formation of one univalent pair, and occasionally two univalent pairs. No specific chromosome pair was preferentially involved. The wheat genes could not be transferred to the progeny by selfing nor by reciprocal back-crossing, but gametes without these genes were functional. The plants were semisterile.Key words: wheat chromosome addition, rye, somatic translocation, univalents, mildew resistance.
Isozyme similarity in Thinopyrum and its relatives (Triticeae: Gramineae)
Authors: Jarvie J. K. , Barkworth M. E.
Published: April 2011

Thirty-seven alleles encoded by eight loci from six enzyme systems were numerically analyzed in taxa of Thinopyrum, Lophopyrum, Trichopyrum, and Pseudoroegneria. Thinopyrum and Lophopyrum were similar, and both were distant from Pseudoroegneria. This is consistent with anatomical and genomic evidence, but conflicts with that from morphology. The only extant diploid of Lophopyrum was isolated from other members of its genus. The data suggest that it may have diverged in terms of its isozymes subsequent to the differentiation of the E genome, and its incorporation into the extant alloploids or their ancestors. Alloploids between the E and S genomes showed isozyme patterns resembling those of Pseudoroegneria, reflecting patterns of variation shown by morphological and anatomical data. It is clear that an understanding of the evolutionary relationships in the taxa of Thinopyrum and its relatives requires synthesis of different kinds of evidence.Key words: Triticeae, genomes, isozymes, evolution, genetic resources.
Synaptonemal complex formation in male scorpions exhibiting achiasmate meiosis and structural heterozygosity
Authors: Shanahan Catherine M. , Hayman David L.
Published: April 2011

Synaptonemal complex (SC) formation was studied in testicular material from individuals of a number of species from two families of Australian scorpions; Buthidae and Scorpionidae. These scorpions exhibit unusual cytogenetic features including achiasmate male meiosis, interchange heterozygosity, and centromeric fusion–fission and inversion heterozygosity. The synaptic behaviour of chromosomes involved in these rearrangements was studied from zygotene to metaphase I, using both meiotic chromosome preparations and techniques for examination of the SCs. Multivalent associations present during the achiasmate meiosis of both buthid and scorpionid scorpions are retained from prophase to metaphase I, unlike those present in polyploid achiasmate Bombyx females. Further evidence suggests that synaptic adjustment does not occur generally in achiasmate scorpionid inversion heterozygotes. However, for some inversions, pairing is seen to become more heterosynaptic from late prophase to metaphase I and this may be related to the pairing maintenance system during achiasmate meiosis in these specialized organisms.Key words: synaptonemal complex, achiasmate meiosis, heterozygosity, interchange, inversion.
Genetic significance of mode of polyploidization: somatic doubling or 2n gametes?
Authors: Watanabe Kazuo , Peloquin Stanley J. , Endo Masatoshi
Published: April 2011

Computer simulation was undertaken to compare the genetic consequences of asexual (somatic doubling) and sexual (2n gametes) polyploidization. The coefficient of inbreeding at a locus, the number and frequency of genotypes at a locus, and the proportion of tri- and tetra-allelic genotypes were considered. The factors considered to estimate the genetic consequences were (i) mechanisms of sexual polyploidization, by first division restitution (FDR) × second division restitution (SDR), FDR × FDR, or SDR × SDR; (ii) position of the locus in relation to the centromere, which affects the gametic output in 2n gamete formation and thus the probability of single-exchange tetrads in meiosis during 2n gamete formation (p value); and (iii) allelic diversity at a locus. In comparing asexual and sexual polyploidization, regardless of the position of a locus in relation to the centromere, sexual polyploidization generally indicated less inbreeding, more genotypic diversity, and a higher proportion of tri- and tetra-allelic genotypes. When allelic diversity at a locus was increased, these characteristics were even more prominent. When only two alleles are possible at a locus, somatic doubling would not be inferior to sexual polyploidization. Overall results favored SDR × FDR and FDR × FDR as a mode and mechanisms of polyploidization. The genetic variations produced by 2n gametes could be attributed to "combining ability of 2n gametes."Key words: asexual polyploidization, sexual polyploidization, inbreeding, heterozygosity, combining ability of 2n gametes.
Abundance and DNA sequence of two-base repeat regions in tropical tree genomes
Authors: Condit Richard , Hubbell Stephen P.
Published: April 2011

Tandem DNA repeats of two-base pairs are potentially important tools for population genetic studies because of their abundance and length variation. As part of our research into the ecology of tropical forest plants, we began a study of dinucleotide repeat regions in several genera of tropical trees. Genomic libraries in bacteriophase λ were screened with the oligonucleotide probes poly(GT) and poly(AG). Both types of repeat regions were abundant in the genomes of all six plant species examined. Using the size of inserts in the phage libraries and number of phage screened, we estimated that there were 5 × 103 to 3 × 105 poly(AC) and poly(AG) sites per genome, with slightly more AG than AC sites. When libraries were made from smaller fragments of genomic DNA, abundance estimates were higher, suggesting that two-base repeat sites were clustered in the genome. Poly(AC) sites were 16–22 bp in length, and four of the five sequenced were adjacent to either poly(AG) or poly(AT) sites. Other repeat regions appeared in DNA flanking the AC sites. This further demonstrated that two-base repeats and other repetitive DNA were clustered in the genome. Two-base repeats are abundant in plant genomes and could provide a large number of polymorphic markers for studies of plant population genetics.Key words: repetitive DNA, dinucleotide repeats, tropical plant genomes.
Cloning and characterisation of a new rye-specific repeated sequence
Authors: Guidet François , Rogowsky Peter , Taylor Christopher , Song Weining , Langridge Peter
Published: April 2011

In this paper we describe a repetitive DNA sequence unique to the rye genome. The corresponding DNA probe (pAW173) was cloned as a 450-bp fragment and does not hybridize to wheat or barley DNA and is not related to five other repeated DNA families characterised in rye. This new family (designated the R173 family) consists of moderately repeated DNA (~ 15 000 units per genome) and is present on all seven rye chromosomes. The hybridization patterns in Southern blots indicate that it is not organised as blocks of tandem arrays and in situ hybridization shows that it is dispersed throughout the rye chromosomes. The probe has been successfully used as a molecular marker in identifying rye genetic material in a wheat background.Key words: repetitive DNA sequence, rye-specific DNA, molecular marker.
Linear mitochondrial molecules and intraspecific mitochondrial genome stability in a species of Pythium
Authors: Martin Frank N.
Published: April 2011

Restriction maps of the mitochondrial genomes of 11 isolates of Pythium oligandrum revealed sizes ranging from 69.8 to 72.7 kb. While most isolates had circular genomes, two isolates contained predominantly linear molecules with the position of the ends corresponding to the small unique region of the circular molecules. The termini of these molecules were resistant to Exo III and λ exonuclease digestion and had hairpin loop structures. Several isolates with circular genomes also appeared to contain what may be a small percentage of linear molecules. The inverted repeat and large unique region were 28.6 and 11.5 kb, respectively, and were equal in size among isolates. The small unique region was the most variable portion of the genome and ranged from 0.98 to 3.92 kb in size. Polymorphisms among isolates were due mainly to insertions–deletions in the small unique region, which not only contributed to size differences but also generated additional unique restriction sites. The only variation detected in the inverted repeat or the large unique region was the addition–loss of several restriction sites in four isolates. Less sequence divergence was observed in the inverted repeat than in the large unique region (maximum of 0.83 compared with 2.50%, respectively). Percent sequence divergence for the entire genome (excluding one arm of the inverted repeat) ranged from 0 to 1.00%. Excluding differences caused by insertions–deletions in the small unique region, 94% or greater of the restriction sites are conserved among all isolates.Key words: Pythium oligandrum, mtDNA, inverted repeat, intraspecific variation, linear genome.
Use of Ipomoea trifida (HBK.) G. Don germ plasm for sweet potato improvement. 1. Development of synthetic hexaploids of I. trifida by ploidy-level manipulations
Authors: Iwanaga Masaru , Freyre Rosanna , Orjeda Gisella
Published: April 2011

Crosses were made between 21 tetraploid accessions and 41 diploid accessions of Ipomoea trifida, obtaining a total of 9185 triploid seeds from 215 different cross combinations. Doubling the somatic chromosome number of the triploids was attempted by colchicine treatment on young seedlings to obtain synthetic hexaploids. A total of 787 axillary buds of 316 triploid plants were treated with a 0.5% colchicine solution for 24 h, applied to cotton plugs surrounding the buds. The survival rate of the treated buds was, on average, 41%. The ploidy level in germ-layer L2 was determined in 258 clones by evaluating a pollen sample from each clone. Fifty-five clones were selected for high stainability and pollen size. The selected genotypes were meiotically analyzed. Twenty-two of them were identified as hexaploid and 33 as triploid with 2n pollen production. The present study is the first report on 2n pollen production in triploid plants of Ipomoea species. The use of these triploid clones with 2n pollen production and synthetic hexaploid clones for sweet-potato breeding is discussed.Key words: Ipomoea batatas, Ipomoea trifida, colchicine, triploids, 2n pollen.
Synaptonemal complex analysis of hybrid cattle. II. Bos indicus × Bos taurus F1 and backcross hybrids
Authors: Dollin A. E. , Murray J. D. , Gillies C. B.
Published: April 2011

The levels of meiotic chromosome pairing abnormalities observed in six Australian F, Bos indicus x Bos taurus cattle crosses (mean = 23%) were significantly higher than those of the full-blood breeds (9%). The abnormal configurations in the F[hybrids included partial pairing failure, multivalents, interlocks, and inversion pairing. Abnormal configurations were also present, but at lower frequency, in backcross hybrid bulls. The main types of abnormal configurations and the levels of XY-autosomal associations and autosomal asynapsis observed were unlikely to cause significant fertility problems in the hybrids.Key words: synaptonemal complex, hybrid cattle, meiosis.
Synaptonemal complex analysis of hybrid cattle. III. Meiotic pairing mechanisms in F1 Brahman × Hereford hybrids
Authors: Dollin A. E. , Murray J. D. , Gillies C. B.
Published: April 2011

The mechanisms of homoeologous chromosome pairing were studied in synaptonemal complex (SC) spreads of F1 Brahman (Bos indicus) × Hereford (Bos taurus) cattle. The most common SC abnormalities were bivalents with partial pairing failure and interlocks. While C-band polymorphisms could underlie most of the SC abnormalities observed in the full-blood cattle, other causes seem also to be contributing in the hybrids. The pattern of the abnormalities indicates that genie differences between the species were probably involved. Pachytene substaging data suggest that in some spreads, early pachytene bivalents with partial pairing failure may achieve complete synapsis or may be converted to interlocks by late pachytene.Key words: synaptonemal complex, hybrid cattle, interlocks.
Mitochondrial DNA variation within and among populations of the mosquito Aedes albopictus
Authors: Kambhampati Srinivas , Rai Karamjit S.
Published: April 2011

A survey of restriction fragment polymorphism in mitochondrial DNA (mtDNA) of 17 populations of the mosquito Aedes albopictus was undertaken. The mtDNA size was estimated to be about 17.5 kbp. The level of polymorphism was low, with over 99% of the fragments being shared in common among the 17 populations. Three populations, Mauritius, Singapore, and Hong Kong, contained individuals with both the ancestral and novel mtDNA haplotypes. We conclude that the low level of mtDNA polymorphism in A. albopictus is a result of recent range expansion and that the mixture of haplotypes is a likely result of human-aided gene flow among populations.Key words: mitochondrial DNA, genetic variation, genetic structure, Aedes albopictus.
Cytogenetics of beavers: a case of speciation by monobrachial centric fusions
Authors: Ward O. G. , Graphodatsky A. S. , Wurster-Hill D. H. , Eremina V. R. , Park J. P. , Yu Q.
Published: April 2011

A comparison of G-banded chromosomes of four North American beavers, Castor canadensis (two males, two females), and four Eurasian beavers, Castor fiber (two males, two females), revealed that extensive monobrachial centric fusions distinguished the karyotypes of the two species. The complex multivalent formations that would occur in meiosis of a hypothetical hybrid would be expected to produce unbalanced gametes and postmating reproductive isolation. Thus, neither species was derived from the other; rather, they likely were derived from isolated populations in which some of the acrocentrics fused independently to produce monobrachial homology.Key words: beaver, chromosomes, karyotype evolution, monobrachial rearrangements, reproductive isolation.
Physical mapping of plant DNA sequences by simultaneous in situ hybridization of two differently labelled fluorescent probes
Authors: Leitch I. J. , Leitch A. R. , Heslop-Harrison J. S.
Published: April 2011

Two haptens, biotin and digoxigenin, were used to label two highly repetitive plant DNA sequences: pTa71 (a clone containing a ribosomal DNA sequence from wheat, Triticum aestivum) and pSc119.2 (a clone containing a 120-bp tandem repeat sequence from rye, Secale cereale). These probes were simultaneously localized by in situ hybridization on chromosome spreads of rye, Secale cereale cv. Petkus Spring. The ability to localize two sequences simultaneously will be of major importance for physically ordering DNA sequences along plant chromosomes.Key words: physical mapping, DNA–DNA in situ hybridization, Secale, fluorescent mapping, multiple labelling.
The Nor-D3 locus of Triticum tauschii: natural variation and genetic linkage to markers in chromosome 5
Authors: Lagudah E. S. , Appels R. , McNeil D.
Published: April 2011

Variation in the intergenic spacer region of the ribosomal RNA genes (located at the Nor locus) was assayed in a collection of 411 accessions of Triticum tauschii from Turkey, USSR, Iran, Afghanisan, Pakistan, and China. Twenty rDNA genotypes were identified and it was demonstrated that T. tauschii accessions from the USSR and Iran have the highest diversity at the Nor locus. At least four of the rDNA genotypes were demonstrated to be alleles of a single major locus, in segregating F2 progeny analyses. The TaqI restriction fragment associated with rDNA genotype 7 was shown to be the same as the Nor-D3a allele present in all bread wheats (based on chromosome location and length of the intergenic spacer region). This genotype was significantly associated with T. t. ssp. strangulata, previously argued to be the donor of the D genome to hexaploid wheat. The Nor locus showed a high level of recombination with the 5SDna-2 locus, which was also located on chromosome 5D. The Nor locus is placed distal to the 5SDna-2 locus but proximal to the grain softness protein gene (XGsp) on the short arm of chromosome 5D.Key words: D genome, Nor-D3, rDNA polymorphism, chromosomal location.
DNA fingerprinting in reptiles: Bkm hybridization patterns in Crocodilia and Chelonia
Authors: Demas Suzanne , Wachtel Stephen
Published: April 2011

The simple tetranucleotide repeat GATA (GACA) occurs in all eukaryotes so far studied. In many species, the arrangement of these sequences varies considerably among individuals. Thus GATA (GACA) type probes produce DNA fingerprints when hybridized with restricted DNA from different individuals within a species. Banded krait minor (Bkm) satellite DNA (related to sequences originally recovered from the W chromosome of the banded krait and consisting essentially of a series of GATA repeats) is found in a wide spectrum of vertebrates and invertebrates. We used the Bkm 2(8) clone to evaluate the occurrence of this satellite in DNA from five species of Crocodilia and six species of Chelonia, including the sea turtles Chelonia mydas and Lepidochelys kempi. Well-resolved DNA fingerprints were obtained. Among the crocodilians, fewer restriction fragments were generated and fewer of the fragments were polymorphic, than among the chelonians, consistent with the view that the crocodilians are less divergent within species. The Bkm 2(8) clone can accordingly be used to advantage in individual, familial, and population studies, and perhaps in the evaluation of taxonomic relationships in these animals. This is of potential value in endangered species such as C. mydas and L. kempi.Key words: DNA fingerprinting, Bkm satellite, reptiles.
Use of double-ditelosomic and normal chromosome 1D recombinant substitution lines to map Sr33 on chromosome arm 1DS in wheat
Authors: Jones S. S. , Dvořák J. , Knott D. R. , Qualset C. O.
Published: April 2011

Chromosome 1D homozygous recombinant substitution lines derived from Triticum aestivum 'Chinese Spring' (cross 1) or 'Chinese Spring' double-ditelosomic 1D (cross 2) hybridized with a disomic substitution line of Triticum tauschii chromosome 1D in 'Chinese Spring' were used to investigate the linkage relationships among Glu-D1, encoding subunits of high molecular weight glutenin storage proteins; Gli-D1, encoding gliadin storage proteins; Sr33, conferring stem rust resistance; and the centromere. Based on analysis of 88 and 91 recombinant substitution lines of crosses 1 and 2, respectively, Sr33 is tightly linked to Gli-D1 on chromosome arm 1DS (5.6 and 7.6% recombination) and less tightly to the centromere (29.6%, cross 2) and to Glu-D1 (40.9 and 39.5%). The order of the loci is Glu-D1 – centromere – Sr33 – Gli-D1.Key words: stem rust resistance, seed storage protein, glutenin, gliadin, Triticum aestivum, Triticum tauschii.
Adjacent II segregation products in B–A translocations of maize
Authors: Kindiger B. , Curtis C. , Beckett J. B.
Published: April 2011

In maize (Zea mays L.), meiotic events in B–A translocations that cause the A chromosome to move to one pole and the A–B and B–A chromosomes to move to the opposite pole result in the production of balanced, functional microspores and megaspores. Meiotic events that allow other combinations of chromosomes to proceed to the two poles (A A–B and A B–A) lead to the production of both duplicate (A A–B) and deficient (B–A) spores. Microspores and often megaspores that are deficient for a segment of the A chromosome are expected to abort. Duplication-bearing gametes usually function through the egg but are less able to compete with the normal gametes in the pollen. Cytological data, and genetic data from pollen, kernel, and seedling counts, were used to identify the production of A A–B gametes by B–A translocation heterozygotes and hyperploids. Adjacent II segregation of the A and A–B chromosomes of B–A heterozygotes and hyperploids has been detected in stocks of several different B–A translocations. Some B–A translocations exhibited a frequency of adjacent II segregation as high as 23%.Key words: Zea mays, adjacent segregation, B chromosomes, translocation.
G banding in two species of grasshopper and its relationship to C, N, and fluorescence banding techniques
Authors: Camacho J. P. M. , Cabrero J. , Viseras E. , Lopez-Leon M. D. , Navas-Castillo J. , Alche J. D.
Published: April 2011

A G banding technique combining trypsin and hot saline treatments was used to analyze the chromosomes of two grasshopper species, Eyprepocnemis plorans and Locusta migratoria, both of which contain both standard and supernumerary heterochromatin. Although this technique does not produce G bands like those in mammalian chromosomes, it serves to characterize heterochromatic regions whose nature has been inferred from other banding techniques (C, N, CMA, and DAPI banding). The light regions revealed by G banding contain GC-rich DNA sequences, the more prominent of which coincide with nucleolus organizer regions (NORs). Furthermore, the proximal heterochromatin in E. plorans was heterogeneous, and the standard and supernumerary heterochromatin showed conspicuous differences in organization. Supernumerary heterochromatin is an exception to the regular patterns shown by the standard heterochromatin. The findings are related to the mechanism of action of these banding techniques.Key words: banding techniques, grasshoppers, Eyprepocnemis plorans, Locusta migratoria.
De nouvelles populations robertsoniennes de souris (Mus musculus domesticus) au nord des Alpes
Authors: Belkhir Khalid , Britton-Davidian Janice , König Barbara
Published: April 2011

New Robertsonian (Rb) populations of the house mouse (Mus musculus domesticus) carrying different combinations of centric fusions are reported in France, Switzerland, and Germany. In Alsace (France), the diploid number varied from 2n = 38 to 34; four fusions were present, with Rb(4.12) homozygous in all populations whereas Rb(5.10), Rb(5.7), or Rb(10.14) were found to be segregating. In Switzerland, only all-acrocentric mice (2n = 40) were present in Bern while Rb(5.7) and Rb(9.16) occurred in Basel. In the Konstanz locality from southern Germany, all the mice were homozygous for nine Rb fusions: Rb(1.18), Rb(2.5), Rb(3.6), Rb(4.12), Rb(7.15), Rb(8.17), Rb(9.14), Rb(10.11), and Rb(13.16). The phylogenetic relationship of these new Rb populations with those already known is discussed.Key words: Robertsonian translocations, house mouse, chromosomes, chromosomal evolution.
Genetic analysis of nuclear DNA restriction fragment patterns
Authors: Gillet Elizabeth M.
Published: April 2011

Restriction fragment length polymorphism (RFLP) analysis in the broad sense is the analysis of differences in restriction fragment pattern produced by defined target segments within or between cell compartments, cell types, etc., in a single individual or in different individuals. Thus both molecular hybridization and DNA amplification by two-primer extension using the polymerase chain reaction can define target segments for RFLP analysis. The two techniques are outlined with special consideration of characteristics important for genetic analysis. The mode of inheritance of restriction fragment patterns as a prerequisite for their use as genetic markers in inheritance studies is explained, leading to criticism of common usage. The importance of internal restriction sites for the determination of allelic variation is stressed. It is shown that, if target segments are under the control of a single nuclear diploid restriction fragment locus, then complete reconstruction of all parental target segments requires controlled crosses between individuals of like restriction fragment pattern.Key words: genetic analysis, inheritance, restriction fragment length polymorphism, controlled cross, polymerase chain reaction.
Cytogenetics of a synthesized allopentaploid (2n = 5x = 100) in the genus Glycine subgenus Glycine
Authors: Singh R. J. , Hymowitz T.
Published: April 2011

The objectives of this study were to provide information on the origin, identification, meiosis, and breeding behavior of a synthesized allopentaploid (2n = 5x = 100) in the genus Glycine (Willd.) subgenus Glycine. The origin of the pentaploid plant was as follows: G. clandestina, 2n = 2x = 40, A1A1 × G. canescens, 2n = 2x = 40, AA (designated as H119), F1 (2n = 2x = 40, AA1) × G. tomentella (2n = 4x = 80, AxAxDD) → F1 (2n = 3x = 60, AAxD (assuming A-genome chromosomes from G. canescens were transmitted)) → 0.1% colchicine treatment → 2n = 6x = 120 (AAAxAxDD) × G. tomentella (2n = 4x = 80, AxAxDD) → BC1, 2n = 5x = 100 (AAxAxDD). Morphologically, the pentaploid plant very closely resembled the tetraploid G. tomentella, PI 441005. Compared with hexaploids, the pentaploid plant was less vigorous for several morphological traits. However, it was not possible to distinguish visually among 4x, 5x, and 6x plants. Intergenomic chromosome pairing was followed in hexaploid (A–A, Ax–Ax, D–D) and pentaploid (A, Ax–Ax, D–D) plants. Despite a close similarity between A and Ax genomes (A- and Ax-genome chromosomes pair normally in the absence of their homologues) meiotic stages were highly abnormal in the pentaploid, with univalents, laggards, and micronuclei, but the plant set normal pods and seeds. The pentaploid plant did not breed true, as chromosomes in the 14 examined plants of the progeny ranged from 2n = 86 to 97. Furthermore, progeny of a plant with 2n = 90 segregated for plants with 2n = 81–86. These results indicate that the preferential elimination of G. canescens (A genome) chromosomes is rapid and eventually AxAxDD genome chromosomes will prevail. Thus, pentaploids will stabilize at the tetraploid level.Key words: Glycine spp., allopolyploidy, chromosome pairing, genome.
Hérédité du pourcentage de protéines et mise en évidence de deux nouveaux marqueurs génétiques chez le blé dur
Authors: Lapoujade P. , Ecochard R. , Sarrafi A.
Published: April 2011

Crosses were made between two tetraploid wheats, Ensat-508, an Ethiopian line with a high percentage of protein, and 'Opale', a French cultivar obtained in our laboratory. Reciprocal F1, F2, and backcrosses and the parents were grown in a greenhouse, and the heredity of percentage of grain protein was determined. Reciprocal effects were not significant; narrow- and broad-sense heritabilities were rather high (37.89 and 69.83%, respectively). Ensat-508 has brown, hairy (i.e., with a long pilose brush at the apical end) kernels whereas 'Opale' has amber, glabrous kernels. Our studies show that hairiness of kernels is controlled by a gene with intermediate dominance (proposed designation: Hgr) and brown color of kernels by a dominant gene (temporary designation: Br). Considering the high correlations observed between these two characters and the percentage of grain protein, both Hgr and Br genes should be considered as new genetic markers for breeding programs. Selection for hairy kernel in progenies should improve the percentage of protein.Key words: protein, hairy kernel, markers, linkage.
Rye–wheat hybrids: the production of wheat chromosome additions to rye
Authors: Baum M.
Published: April 2011

To produce rye–wheat addition lines, 21-chromosome rye–wheat hybrids were produced by crossing tetraploid triticale with diploid rye. The subsequent selfing of the hybrids lead to monosomic and double monosomic wheat additions to rye. Screening of the progeny was carried out using the C-banding technique. The wheat additions can be fertile. Wheat chromosome 6B was the chromosome most frequently added to rye. Ribosomal spacer probe pTa250.4 was used to confirm the results obtained by C-banding for the 6B wheat additions to rye. Embryos of the 21-chromosome rye–wheat hybrids showed a good potential for propagating more plantlets after they had been transferred to artificial medium.Key words: rye–wheat addition lines.
Cytogenetics of Elymus caucasicus and Elymus longearistatus (Poaceae: Triticeae)
Authors: Jensen Kevin B. , Wang Richard R.-C.
Published: April 2011

Two accessions of Elymus caucasicus (Koch) Tzvelev and three accessions of Elymus longearistatus (Boiss.) Tzvelev were studied to determine the meiotic behavior and chromosome pairing in the two taxa, their interspecific hybrid, and their hybrids with various "analyzer" parents. Interspecific and intergeneric hybrids of the target taxa were obtained with the following analyzer species: Pseudoroegneria spicata (Pursh) A. Löve (2n = 14, SS), Pseudoroegneria libanotica (Hackel) D. R. Dewey (2n = 14, SS), Hordeum violaceum Boiss. &Hohenacker (2n = 14, HH) (= Critesion violaceum (Boiss. &Hohenacker) A. Löve), Elymus lanceolatus (Scribn. &Smith) Gould (2n = 28, SSHH), Elymus abolinii (Drob.) Tzvelev (2n = 28, SSYY), Elymus pendulinus (Nevski) Tzvelev (2n = 28, SSYY), Elymus fedtschenkoi Tzvelev (2n = 28, SSYY), Elymus panormitanus (Parl.) Tzvelev (2n = 28, SSYY), and Elymus drobovii (Nevski) Tzvelev (2n = 42, SSHHYY). Cytological analysis of their F1 hybrids showed that E. caucasicus and E. longearistatus were allotetraploids comprising the same basic genomes. Chromosome pairing in the E. caucasicus × P. libanotica hybrid demonstrated that the target taxa contained the S genome, based on 6.1 bivalents per cell. The lack of chromosome pairing, less than one bivalent per cell, in the E. longearistatus × H. violaceum hybrid showed that the H genome was absent. Increased pairing in the tetraploid and pentaploid hybrids when the Y genome was introduced indicated that the second genome in the two taxa was a segmental homolog of the Y genome. The S and Y genomes in E. caucasicus and E. longearistatus have diverged from each other and from those in many of the eastern and central Asian SY tetraploids.Key words: genome, meiosis, chromosome pairing, morphology, hybrid, Triticeae.
Exploitation of a preferentially transmitted chromosome from Aegilops sharonensis for the elimination of segregation for height in semidwarf bread wheat varieties
Authors: King I. P. , Koebner R. M. D. , Schlegel R. , Reader S. M. , Miller T. E. , Law C. N.
Published: April 2011

Certain semidwarf bread wheat varieties tend to lose chromosome 4D, carrying the dwarfing gene Rht2, resulting in the production of tall "offtypes." To overcome this problem translocations have been isolated involving the arm of the Aegilops sharonensis chromosome 4S1 that carries the genes determining preferential transmission and the Rht2-carrying arm of chromosome 4D of Triticum aestivum. These translocations, which were derived by self-pollinating plants doubly monosomic for chromosomes 4D and 4S1, appear to be preferentially transmitted in both pollen and egg, thus ensuring constant disomy and homozygosity of Rht2.Key words: preferential transmission, translocation, Triticum aestivum, Aegilops sharonensis.
Genetic segregation of random amplified polymorphic DNA in diploid cultivated alfalfa
Authors: Echt C. S. , Erdahl L. A. , McCoy T. J.
Published: April 2011

Polymerase chain reaction was used, with single 10-mer primers of arbitrary sequence, to amplify random regions of genomic DNA from a diploid cultivated alfalfa backcross population. Segregation of the random amplified polymorphic DNA (RAPD) fragments was analysed to determine if RAPD markers are suitable for use as genetic markers. Of the 19 primers tested, 13 amplified a total of 37 polymorphic fragments, of which 28 (76%) segregated as dominant Mendelian traits. RAPD markers appear useful for the rapid development of genetic information in species like alfalfa where little information currently exists or is difficult to obtain.Key words: random amplified polymorphic DNA, polymerase chain reaction amplification, genome mapping, restriction fragment length polymorphism, Medicago sativa.
Analysis of intergenic spacer regions in the nuclear rDNA of Pharbitis nil
Authors: Katayama Sumiko , Hirano Hiro-Yuki , Tsukaya Hirokazu , Naito Satoshi , Komeda Yoshibumi
Published: April 2011

The nucleotide sequence of a 4.2-kb EcoRI fragment from the intergenic region between the genes for 25S and 18S ribosomal RNA of Pharbitis nil Choisy was determined. The region contained a unique repetitive family of DNA sequences, called the RsaI family, composed of 32-bp units. The 32-bp unit was tandemly repeated in the intergenic region, and four subfamilies of repeating units were clustered as discrete blocks. The RsaI family of repeats was shown to be specific to the genus Pharbitis by Southern blot hybridization.Key words: Pharbitis nil Choisy, rDNA intergenic spacer, RsaI family.
Chromosomal location of adenylate kinase, 6-phosphogluconate dehydrogenase, and glutamate-pyruvate transaminase structural loci in wheat, barley, and Lophopyrum elongatum
Authors: Sun Mei , Dvořák Jan
Published: April 2011

The chromosome locations of loci encoding isozymes of adenylate kinase, EC 2.7.4.3 (ADK), 6-phosphogluconate dehydrogenase, EC 1.1.1.44 (PGD), and glutamate–pyruvate transaminase, EC 2.6.1.2 (GPT) were investigated in wheat (Triticum aestivum L.), Lophopyrum elongatum (Host) Löve, and barley (Hordeum vulgare L.). Loci encoding ADK-1 are on homoeologous chromosome arms 7AL, 7BL, and 7DL in wheat, chromosome arm 7Eβ in L. elongatum, and chromosome arm 7HS in barley. The loci are designated Adk-A1, Adk-B1, Adk-D1, Adk-E1, and Adk-H1, respectively. The Adk-D1 locus is proximal in the linkage group of chromosome arm 7DL and is 24 cM from proximal locus Rc3 on the chromosome arm 7DS. A second locus, Adk-2, is on chromosome arm 6HL in barley. Locus Pgd-E2 in L. elongatum is on the long arm of chromosome 1E. This assignment agrees with the location of the barley Pgd-2 locus on the long arm of barley chromosome 1H. An attempt to assign loci encoding PGD-2 to wheat chromosomes was unsuccessful, presumably owing to gene triplication. Isozyme GPT-1 is encoded by structural genes on L. elongatum chromosome arm 1ES and tentatively on wheat chromosome arms 1AS, 1BS, and 1DS. The loci are designated Gpt-A1, Gpt-B1, Gpt-D1, and Gpt-E1, respectively. Circumstantial evidence suggests that GPT-1 is also encoded by barley chromosome 1H.Key words: Triticum, Agropyron, Hordeum, linkage.
Organization and evolution of higher plant nuclear genomes
Authors: Lapitanz Nora L. V.
Published: April 2011

The knowledge gained from studies on eukaryotic genome organization is important for understanding how genomes function and evolve, and it provides the basis for designing strategies for manipulating genomes. Hence, numerous studies on this subject have been conducted over the years, utilizing a variety of methods. In the recent decade, several techniques have been developed that allow the study of eukaryotic genome organization at different levels. Molecular techniques including molecular cloning, DNA sequencing, restriction fragment length polymorphism mapping, in situ hybridization, and pulsed field gel electrophoresis together provide a means of obtaining a comprehensive and detailed view of eukaryotic genomes. This paper summarizes recent findings on the organization and evolution of the nuclear genomes of higher plants, with emphasis on representative species with varying genome sizes, including Arabidopsis thaliana, tomato, maize, and wheat. Common, as well as unique, features in the organization of repeated DNA sequences and low copy sequences in these genomes are described and their evolutionary significance discussed.Key words: genome organization, evolution, higher plants, repeated DNA sequences, low copy number sequences.