bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct comparison of levels of genetic variation in tomato detected by a GACA-containing microsatellite probe and by random amplified polymorphic DNA
Authors: Rus-Kortekaas W. , Smulders M. J. M. , Arens P. , Vosman B.
Published: May 2008

In this study, a direct comparison was made of the ability of four selected random amplified polymorphic DNA (RAPD) primers and a GACA-containing microsatellite probe to detect genetic variation in Lycopersicon. Of the 89 RAPD primers initially tested, 85 showed differences between a representative of Lycopersicon pennellii and L. esculentum, but only 4 distinguished among three L. esculentum cultivars. These four primers were subsequently tested on representatives of six Lycopersicon species. In pairwise comparisons of species, all or 14 of the 15 combinations could be distinguished by single primers. When the primers were tested on 15 L. esculentum cultivars, 90 of the 105 combinations could be distinguished by the four primers together. Finally, none of 118 tested primers showed reproducible differences among calli or progeny of régénérants from tissue culture, although some of the plants had inherited morphological mutations. The probe pWVA16, which detects GACA-containing microsatellites, could distinguish in TaqI-digested DNA the representatives of Lycopersicon species as well as all the L. esculentum cultivars tested. The probe was unable to detect polymorphisms among calli and the progeny of regenerants from tissue culture. An analysis of the results showed that the four selected RAPD primers were able to detect polymorphic bands among species at a frequency of 80%, and among cultivars at a frequency of 44%. In contrast, the microsatellite probe detected polymorphic bands at a frequency of 100 and 95%, respectively. The GACA-containing probe did not detect any common bands among the representatives of the six species, while band sharing with RAPDs was 48%. These results indicate that the two methods detect two types of DNA that differ in their degree of variability.Key words: DNA fingerprint, RAPD, simple sequence, somaclonal variation, tissue culture.
Comparative RFLP mapping of a wild rice, Oryza officinalis, and cultivated rice, O. sativa
Authors: Jena K. K. , Khush G. S. , Kochert G.
Published: May 2008

A comparative RFLP map was constructed in a wild rice, Oryza officinalis, by using 139 genomic and cDNA probes that had been used previously to map RFLPs in O. sativa. Nine of the 12 chromosomes of O. officinalis were highly homosequential to those of O. sativa. A major rearrangement of gene order was detected in chromosome 1 and small inversions were found in chromosomes 3 and 11. Fourteen translocated RFLP markers were found, and chromosome 11 contained a high frequency of such translocated segments. Results were consistent with meiotic and trisomie analysis, which suggested that the genomes of O. officinalis and O. sativa were similar. Applications of comparative maps in plant breeding and gene cloning are discussed.Key words: Oryza, rice, wild rice, RFLP, genetic map.
Cytogenetic variation in natural populations of the Old World screwworm fly Chrysomya bezziana (Diptera: Calliphoridae)
Authors: Bedo D. G. , Spradbery J. P. , Mahon R. J.
Published: May 2008

The existence of sibling species in the Old World screwworm fly Chrysomya bezziana would raise serious problems in eradicating this pest if it entered Australia. Cytogenetic variation in C. bezziana was investigated by analyzing pupal trichogen polytene chromosomes. Natural populations of C. bezziana spanning its range from southern Africa to Papua New Guinea were examined as well as hybrids between a New Guinea laboratory strain and natural populations. No evidence of sibling species was found. All populations exhibited the same basic banding pattern as the standard sequence established from a Papua New Guinea strain. Extensive asynapsis of chromosome homologues was found in some hybrid crosses and was therefore measured in all populations and hybrids to detect systematic variation. Asynapsis levels in most hybrids could not be statistically distinguished from those present in the parent populations except for crosses between populations at the ends of the range. This result does not permit asynapsis levels to be used in establishing the origin of introduced flies by estimating their distance from known populations. One inversion polymorphism and six band polymorphisms spread over three chromosomes were analyzed. Populations in each sampled region had characteristic combinations of band polymorphisms. This may offer a diagnostic method for determining the origin of flies accidentally introduced to Australia.Key words: Chrysomya bezziana, screwworm, polytene chromosomes, asynapsis.
Cytological and molecular evidence of deletion of ribosomal RNA genes in chromosome 6 of barley (Hordeum vulgare)
Authors: Gecheff K. , Hvarleva T. , Georgiev S. , Wilkes T. , Karp A.
Published: May 2008

The barley chromosomal mutant T-35, in which only one pair of satellite chromosomes is apparent, was analyzed using a range of cytological and molecular techniques. Using conventional Feulgen staining, Giemsa and silver banding, in situ hybridization, and Southern blot analysis, unequivocal cytological and molecular evidence was obtained that T-35 is a homozygous deletion of rRNA genes residing in the nucleolus organizer region (NOR) of chromosome 6. According to the criteria of arm ratio and Giemsa-banding pattern of this chromosome, the deletion involved the whole NOR, one of the breakpoints being localized in the short arm proximally to the NOR-associated heterochromatic band, the other probably in the satellite of the chromosome. As a result of this deletion, an increased activity of the rRNA genes (as indicated by the size of the silver bands) on the other NOR-bearing chromosome (chromosome 7) was observed. The possible reasons for this phenomenon are discussed.Key words: barley, nucleolar organizing region, deletion, silver and Giemsa banding, in situ hybridization.
Genetics of adult-plant leaf-rust resistance in four Indian and two Australian bread wheat cultivars
Authors: Shiwani F , Saini R. G.
Published: May 2008

Genetic studies for leaf-rust resistance were conducted on four Indian (CPAN1235, HD2135, HP1209, and VL404) and two Australian (CSP44 and Oxley) bread wheat cultivars. The F2 and F3 plants from their crosses with each other and with susceptible cultivar Agra Local were tested against a mixture of pathotypes 77-1 and 77-2 (variants of race 77). Disease scores on F1's from resistant/susceptible parent crosses indicated partial dominance of resistance in these wheats. The six cultivars have two adult-plant resistance genes each. Their intercrosses revealed similar resistance gene(s) in CSP44 and Oxley, and CPAN1235 and HP1209. The six wheats appear to carry at least seven diverse leaf-rust resistance genes (temporarily named LrI to LrO) against pathotypes 77-1 + 77-2. Adult-plant resistance is additive and therefore the combinations of partially effective resistance genes identified in this study can provide higher levels of resistance. Because these genes are of hexaploid origin, they can be easily exploited in breeding programs. Furthermore, two or more resistance genes from the six wheat cultivars when combined with Lr34 are likely to impart durable resistance to leaf rust.Key words: adult-plant resistance, leaf-rust resistance, wheat, Puccinia recondita, Triticum aestivum.
Identification of the stem rust resistance gene Pg9 and its association with crown rust resistance and endosperm proteins in 'Dumont' oat
Authors: Chong J. , Howes N. K. , Brown P. D. , Harder D. E.
Published: May 2008

The Canadian oat cultivar 'Dumont' is known to have genes Pc38 and Pc39 for crown rust resistance and genes Pg2 and Pg13 for stem rust resistance. When crossed to a susceptible oat line OT328, 'Dumont' was shown to have an additional dominant gene for crown rust resistance, designated PcX. Tests of segregating progeny indicated that the stem rust resistance gene Pg9 is present and is tightly linked in coupling to PcX. The presence of Pg9 in 'Dumont' was confirmed in crosses involving the cultivar 'Ukraine', which has Pg9 and a crown rust resistance gene tightly linked to it. The association of rust resistance with endosperm proteins in 'Dumont' was investigated. The linkage of gene Pg13 with a 56.6-kDa polypeptide locus (map distance of 10.47 ± 2.70 cM) was demonstrated using sodium dodecylsulfate – polyacrylamide gel electrophoresis (SDS–PAGE). A 27.9-kDa polypeptide was shown to be associated with the linked PcX/Pg9 loci by SDS–PAGE but appeared to be more reliably separated as an avenin band, designated B4, using acid–PAGE. Another avenin band, designated B2, also was shown to be associated with the PcX/Pg9 loci using acid–PAGE. The loci conditioning the B2 and B4 bands appeared to be tightly linked or allelic and are separated from the linked PcX/Pg9 loci by a map distance of 1.03 ± 0.36 cM. The association of Pg13 with a 56.6-kDa polypeptide and the tight linkage between PcX/Pg9 and the B2 (in coupling) and B4 (in repulsion) avenin loci offer a useful tool to breeders to detect the presence of these genes in oat breeding.Key words: avenins, gel electrophoresis, molecular markers.
Recombination of alleles conferring specific resistance to powdery mildew at the Mla locus in barley
Authors: Mahadevappa Mamatha , DeScenzo Richard A. , Wise Roger P.
Published: May 2008

In barley (Hordeum vulgare L.), the Mla locus conditions reaction to the powdery mildew fungus Erysiphe graminis f.sp. hordei. Enrichment for genetic recombinants in the Mla region is possible by screening for recombination events between the flanking endosperm storage proteins hordeins C and B. Reciprocal crosses were made between the Franger (C.I. 16151) and Rupee (C.I. 16155) lines carrying the (Mla6 + Mla14) and Mla13 alleles, respectively. Recombinants were identified from F2 segregants by analyzing the extracted hordein polypeptides by sodium dodecyl sulphate – polyacrylamide gel electrophoresis. Two hundred and seventy-six recombinant gametes were identified from the 1800 seeds that were screened. Recombination of Mla alleles was analyzed by inoculating F4 recombinant lines with three isolates of E. graminis (A27, 5874, and CR3), which recognize specific Mla alleles. The linkage order established is Hor1–Mla6–Mla13–Mla14–Hor2. The genetic distances between Hor1–Mla6, Mla6–Mla13, and Mla13–Hor2, obtained using Mapmaker 3.0b F3 intercross analysis, are 3.9, 0.2, and 5.2 cM, respectively.Key words: recombinant, barley, powdery mildew, Mla, hordein.
C-banding and fluorescence in situ hybridization studies of the wheat–alien hybrid 'Agrotana'
Authors: Xu Jie , Conner R. L. , Laroche A.
Published: May 2008

'Agrotana', a wheat-alien hybrid (2n = 56), is a potential source of resistance to common root rot, stem rust, wheat streak mosaic virus, and the wheat curl mite. However, the origin of 'Agrotana', reported to be durum wheat × Agropyron trichophorum (pubescent wheatgrass), is uncertain. The objective of this investigation was to determine the chromosome constitution of 'Agrotana' using C-banding and fluorescence in situ hybridization techniques. The F1 hybrid of 'Agrotana' × 'Chinese Spring' wheat showed 7 I + 21 II in 14.9% of the pollen mother cells, evidence of the presence of the A, B, and D genomes in 'Agrotana'. The hybrid had 16 heavily C-banded chromosomes, namely 4A, and 1-7B of wheat, and a translocation that probably involved wheat chromosomes 2A and 2D. In situ hybridization using biotinylated genomic DNA of Ag. trichophorum cv. Greenleaf blocked with CS DNA failed to identify the alien chromosomes in 'Agrotana', indicating that the alien chromosomes were not likely derived from pubescent wheatgrass. In situ hybridization using labelled wheat genomic DNA blocked with 'Agrotana' DNA revealed that 'Agrotana' had 40 wheat, 14 alien, and 2 (a pair) wheat–alien translocated chromosomes. There was no homology between wheat and the alien chromosomes or chromosome segments involved in the wheat–alien recombinant. Two of the seven pairs of alien chromosomes were homoeologous to each other. The ability to identify alien chromatin in wheat using labelled wheat DNA instead of labelled alien DNA will be particularly useful in chromosome engineering of wheat germplasms having alien chromatin of unknown origin.Key words: wheat–alien hybrid, C-banding, fluorescence in situ hybridization, labelled wheat DNA as probe.
Meiosis in allopolyploid Crepis capillaris. II. Autotetraploids
Authors: Jones G. H. , Vincent J. E.
Published: May 2008

Meiotic chromosome pairing of autotetraploid Crepis capillaris was analysed by electron microscopy of surface-spread prophase I nuclei and compared with light microscopic observations of metaphase I chromosome configurations. Prophase I quadrivalent frequencies are high in all three tetrasomes. (A, D, and C) and partially dependent on chromosome size. At metaphase I quadrivalent frequencies are much lower and strongly dependent on chromosome size. There is no evidence for multivalent elimination during prophase I in this system, and the reduction in multivalent frequency at metaphase I can be explained by an insufficiency of appropriately placed chiasmata. The high frequencies of prophase I quadrivalents far exceed the two-thirds expected on a simple model with two terminal independent pairing initiation sites per tetrasome, suggesting that multiple pairing initiation occurs. Direct observations reveal relatively high frequencies of pairing partner switches (PPSs) at prophase I, which confirms this suggestion. The numbers of PPSs per tetrasome show a good fit to the Poisson distribution, and their positional distribution along chromosomes is random and nonlocalized. These observations favour a model of pairing initiation based on a large number of evenly distributed autonomous pairing sites each with a uniform and low probability of generating a PPS.Key words: autotetraploid, meiosis, Crepis capillaris, multivalent, pairing partner switch.
A method for detecting DNA polymorphism in large populations
Authors: Aitken S. A. , Tinker N. A. , Mather D. E. , Fortin M. G.
Published: May 2008

Molecular markers linked to loci of interest can be used for fine mapping a particular area of a genome or for marker-assisted selection. We present an approach for screening individual plants with polymorphic markers that facilitates phenotyping in large populations. Polymorphic DNA fragments, amplified by PCR, are labelled with digoxigenin and used as probes on slot blots of amplified DNA from the individual plants to be tested. DNA is obtained by a simple two-tube purification method. The colorimetric detection of alleles on the blots is more reliable, and more amenable to automation, than conventional staining of electrophoresis gels.Key words: molecular markers, RAPD, genetic mapping, breeding.
Construction and expression of a metallothionein–β-glucuronidase gene fusion
Authors: Hattori Jiro , Labbé Hélène , Miki Brian L.
Published: May 2008

A gene fusion consisting of the Chinese hamster metallothionein II and β-glucuronidase coding regions was constructed. The fusion protein expressed in Escherichia coli retained cadmium-binding capacity and β-glucuronidase activity. When expressed from the constitutive 35S promoter in transgenic tobacco, the levels of 109Cd accumulation in leaves were reduced to about 70% of those in untransformed control plants. Metallothionin-pJ-glucuronidase did not sequester a significant proportion of the leaf 109Cd taken up through the roots in vitro and therefore a sink for Cd was not created.Key words: metallothionein–β-glucuronidase fusion, cadmium, transgenic plants.
(dA–dC)n∙(dG–dT)n repeats mark the boundaries of a recent insertion event into a subgroup of Xenopus laevis hsp 30 gene promoters
Authors: Ali Adnan , Krone Patrick H. , Heikkila John J.
Published: May 2008

The Xenopus laevis hsp 30 gene family (encoding the 30-kDa heat shock proteins) consists of at least seven closely related members that are tandemly arranged in one or more clusters within the genome. This gene family appears to have been generated by a number of independent duplication events, each of which gave rise to one or more of the known members of the family. We report here the characterization of a genomic fragment that bears a high degree of similarity to a 192-bp region of the promoters of two hsp 30 genes (hsp 30A and hsp 30C) but not the promoters of any of the other hsp 30 genes isolated to date. The rest of this clone has no significant similarity to any other region of the hsp 30A and hsp 30C genes. It appears to represent a region of the genome that has undergone both duplication and subsequent insertion events fairly recently during the evolution of Xenopus laevis. Interestingly, the boundary regions of the insertion are marked by potential Z-DNA forming blocks of seven and nine perfect 5′-AC-3′ dinucleotide repeats.Key words: Z-DNA, gene duplication, recombination.
Genetic applications of transposable elements in eukaryotes
Authors: Lai Chaoqiang
Published: May 2008

Transposable elements have many potential applications in genetic research, including insertional mutagenesis, gene mapping, gene cloning, gene transfer within and between species, and identification of genes expressed in specific tissues at a particular time. All these genetic approaches are important in the study of molecular biology and evolution. As the number of known transposable element families increases and their properties are further documented, their utility as genetic research tools will become greater. The purpose of this article is to discuss the salient properties of transposable elements in eukaryotes and their applications to genetic research.Key words: transposable elements, mutagenesis, plants, Drosophila, genetic application.
Transposition of minisatellite-like DNA in Chironomus midges
Authors: Hankeln Thomas , Rohwedder Angela , Weich Bettina , Schmidt Erwin R.
Published: May 2008

Cla elements are a family of tandem repetitive DNA sequences present in the genome of several Chironomus species. Interspersed clusters of Cla elements are widely distributed all over the chromosomes in C. thummi thummi, while they seem to be limited to the centromeric regions in the closely related subspecies C. t. piger. Here we present molecular evidence that this differential distribution is due to a transposition of Cla elements during evolution of the C. t. thummi genome. We have cloned a "filled" integration site (containing a Cla element cluster) from C. t. thummi and the corresponding "empty" genomic site from C. t. piger and other related species. The comparison shows that tandem repetitive elements may be mobilized together with flanking DNA.Key words: minisatellites, transposition, Chironomus.
Polymerase chain reaction mediated localization of RFLP clones to microisolated translocation chromosomes of barley
Authors: Sorokin A. , Marthe F. , Houben A. , Pich U. , Graner A. , Künzel G.
Published: May 2008

A new strategy has been devised and used for the physical localization of genetically mapped restriction fragment length polymorphism (RFLP) clones to barley chromosomes. Morphologically distinct translocation chromosomes from synchronized root-tip meristems were microisolated and their DNA was used as a template for polymerase chain reaction with sequence-specific primers. Four RFLP clones were assigned to cytologically defined segments of chromosome 5. This related approximately one-third of the map length of linkage group 5 to approximately one-fifth of the mitotic metaphase length of chromosome 5. The technique may substantially contribute to the connection of the RFLP-based genetic linkage maps with cytological markers of the barley chromosomes.Key words: Hordeum vulgare, microisolated chromosomes, translocation, polymerase chain reaction, physical RFLP mapping.
Associated chromosomal DNA changes in polyploids
Authors: Raina S. N. , Parida A. , Koul K. K. , Salimath S. S. , Bisht M. S. , Raja V. , Khoshoo T. N.
Published: May 2008

The 2C and 4C nuclear DNA amounts were estimated in eight diploid species, belonging to three diverse genera (Vicia, Tephrosia, and Phlox) and their corresponding colchitetraploids. In P. drummondii, T. purpurea, and T. oxygona tetraploids the deviation from the expectation was highly significant. The DNA in P. drummondii was further discarded in subsequent (C1, C2) generations, thus attaining an overall reduction of about 25%. The DNA content in the subsequent generations was the same as that of C2. It is concluded that rapid DNA loss in the first and subsequent generations was not only associated with the substantial increase (30–66%) in the seed set, but it also helped in the establishment and stabilization of the tetraploid. The possible relationship between such a nucleotypic change and success of polyploids is discussed. The DNA change from the expected value in the P. drummondii tetraploid was achieved by equal decrement to each chromosome independent of size, i.e., small chromosomes loose the same amount of DNA as the large chromosomes.Key words: colchitetraploid, genome size, DNA loss, seed fertility, stability, DNA distribution.
Differentiation of nearly identical germplasm accessions by a combination of molecular and morphologic analyses
Authors: Waycott W. , Fort S. B.
Published: May 2008

Polymerase chain reaction (PCR) based random amplified polymorphic DNA (RAPD) markers were used to study the extent of redundancy (duplication of genetic materials) within a genetic resources collection. Nine nearly phenotypically and identical accessions of butterhead lettuce (Lactuca sativa L.) were assayed for their genetic identities. A nonuniform, heterogeneous butterhead line and a crisphead cultivar were added for population comparison. PCR amplification using 13 oligonucleotide primers generated 93 polymorphic bands. The percentage of segregating bands was used to determine within-line variation; values ranged from 0.0 to 12.0%, except for the nonuniform line at 22.6%. Between-line similarity was measured using similarity coefficients and ranged from 0.919 to 0.985. The relationship between the crisphead accession and a composite of all butterhead accessions was 0.84. Selfed progeny of each line were measured for morphological uniformity. The variation obtained from these biological data was compared with variation detected at the DNA level and each was positively correlated. Results demonstrate that RAPD analyses may serve as a major source of information for separation of closely related accessions, especially when integrated with phenotypic measures.Key words: genetic resources, phenetics, lettuce, RAPD, morphological variation.
Spontaneous duplication loss and breakage in Caenorhabditis elegans
Authors: McKim Kim S. , Rose Ann M.
Published: May 2008

Duplications in Caenorhabditis elegans spontaneously delete at frequencies ranging from 10−4 to 10−5. We have analyzed the structure and mitotic stability of 33 deleted duplications resulting from spontaneous breakage events. (i) Breakage usually occurred at a variety of sites; that is, there were no hot spots for breakage. An exception was the spontaneous breakage of the X chromosome into which hDp14 was inserted. These breaks were close to or at the site of the chromosome I insertion; therefore, the insertion created a type of fragile site. (ii) Spontaneous duplications often had complex structures. In some cases, their structures were most simply resolved by proposing that the progenitor duplication was a ring chromosome with a superimposed inversion. Most of the proposed ring chromosomes were mitotically unstable, suggesting that ring structures increase the frequency of chromosome loss, (iii) Clusters of spontaneous deletion events were rarely observed, suggesting that the majority of spontaneous breakage events probably occurred during meiosis. (iv) A minority of the spontaneous breakage events were associated with linkage to an autosome. Like free duplications of chromosome I, these linked duplications tended to segregate from the X chromosome in males. (v) Three meiotic mutants, him-3, him-6, and him-8, had no effect on somatic loss of the duplications but did reduce the frequency of breakage events. Given the conclusion that chromosome breakage is a meiotic event, these data are consistent with the function of the three meiotic genes being restricted to meiosis.Key words: chromosome structure, duplication, mitosis, meiosis, Caenorhabditis species.
Genomic in situ hybridization in Avena sativa
Authors: Chen Qianfa , Armstrong Ken
Published: May 2008

Genomic fluorescent in situ hybridization was employed in the study of the genome organization and evolution of hexaploid oat (Avena sativa L. cv. Sun II, AACCDD, 2n = 6x = 42). Genomic DNAs from two diploid oat species, Avena strigosa (genomic constitution AsAs, 2n = 14) and Avena pilosa (genomic constitution CpCp, 2n = 14), were used as probes in the study. The DNA from A. strigosa labelled 28 of the 42 (2/3) chromosomes of the hexaploid oat, while 14 of the 42 (1/3) chromosomes were labelled with A. pilosa DNA, indicating a close relationship between the A and D genomes. Results also suggested that at least 18 chromosomes (9 pairs) were involved in intergenomic interchanges between the A and C genomes.Key words: oats, Avena sativa L., in situ hybridization, fluorescein isothiocyanate, genome organization.
A comparative analysis of genetic polymorphism in wild and cultivated barley from Tibet using isozyme and ribosomal DNA markers
Authors: Zhang Qifa , Yang G. P. , Dai Xiankai , Sun J. Z.
Published: May 2008

This study was conducted to address some of the issues concerning the possible significance of Tibet in the origin and evolution of cultivated barley. A total of 1757 barley accessions from Tibet, including 1496 entries of Hordeum vulgare ssp. vulgare (HV), 229 entries of the six-rowed wild barley H. vulgare ssp. agriocrithon (HA), and 32 entries of the two-rowed wild barley H. vulgare ssp. spontaneum (HS), were assayed for allozymes at four esterase loci. A subsample of 491 accessions was surveyed for spacer-length polymorphism at two ribosomal DNA loci. Genetic variation is extensive in these barley groups, and the amount of genetic diversity in cultivated barley of this region is comparable with that of cultivated barley worldwide. The level of genetic variation of HA is significantly lower than the other two barley groups, and there is also substantial heterogeneity in the level of polymorphism among different agrigeographical subregions. However, little genetic differentiation was detected among the three barley groups (HV, HA, and HS), as well as among different agrigeographical subregions. Comparison of the results from this and previous studies indicated a strong differentiation between Oriental and Occidental barley, thus favoring the hypothesis of a diphyletic origin of cultivated barley.Key words: Hordeum, allozyme, rDNA spacer-length variation, centre of diversity, phylogeny.
Genome size variation in Pisum sativum
Authors: Greilhuber J. , Ebert I.
Published: May 2008

Pisum sativum L. is one of the plant species where infraspecific genome size variation, up to 1.29-fold between cultivars, has been reported. The present investigation deals with a Feulgen cytophotometric analysis of this phenomenon in 25 wild accessions, landraces, and cultivars of widely different geographic origin. Differences between accessions were maximally 1.054-fold in single experiments but proved to be nonreproducible upon repeated measurements. Seedlings of the same accession often differed significantly, up to 1.056-fold, but values from root and shoot tips in one individual were not significantly correlated, indicating the absence of true genome size variation between plants. Upon calibration against Allium cepa a 1C value of 4.42 pg is estimated for Pisum sativum. Altogether the data suggest that, contrary to the divergence in the literature data and recent reports on DNA content variation, the pea has a stable genome size.Key words: Pisum sativum L., genome size variation, Feulgen cytophotometry.
Chromosome banding patterns in the annual species of Cicer
Authors: Tayyar R. I. , Lukaszewski A. J. , Waines J. G.
Published: May 2008

Somatic karyotypes of the nine annual species of Cicer (2n = 16) were analyzed using C-banding. Highly significant differences in haploid genome length and C-band positive heterochromatin content were observed. The haploid genome length ranged from 20.0 μm in the wild species C. judaicum to 28.7 μm in the cultivated species C. arietinum, and significant differences for this character were observed between accessions within several species. Based on their heterochromatin content, the species were divided into two groups: low heterochromatin content (average of 41.7%), which included C. arietinum, C. chorassanicum, C. echinospermum, C. judaicum, C. pinnatifidum, C. reticulatum, and C. yamashitae, and high heterochromatin content (average of 59.5%), which included C. bijugum and C. cuneatum. Within-group variation for heterochromatin content was insignificant, while differences between groups were highly significant. There seemed to be a trend for reduction in C-heterochromatin content in the course of evolution in Cicer. In all species studied, C-bands were located proximally around the centromere with occasional bands in intercalary and distal positions. C-banding patterns allowed for chromosome identification and matching pairs of homologues in all species analyzed.Key words: C-banding, chickpea, heterochromatin, karyotype.
Synaptonemal complex analysis of domestic sheep (Ovis aries) with Robertsonian translocations. I. Pachytene karyotype substaging of normal sheep.
Authors: Dai K. , Dollin A. E. , Gillies C. B.
Published: May 2008

Meiotic chromosome pairing behaviour in three normal sheep was surveyed by synaptonemal complex (SC) analysis at the electron microscope level. The SC karyotype of normal rams is composed of a sex pair, three metacentric or submetacentric pairs, and 23 acrocentric autosomal bivalents, with the total autosomal SC length ranging from 309 to 315 μm. Five nucleoli are terminally located on the three metacentric, and one large and one small acrocentric autosomal bivalents. XY morphology was used to divide pachytene into five substages. Although pairing abnormalities (mostly SC interactions) were recorded in an average of 16% of the spermatocytes, bivalent–XY association occurred in only 4.7% of the cells.Key words: sheep, synaptonemal complex, XY pair, pachytene substaging.
Synaptonemal complex analysis of domestic sheep (Ovis aries) with Robertsonian translocations. II. Trivalent and pairing abnormalities in Massey I and Massey II heterozygotes
Authors: Dai K. , Gillies C. B. , Dollin A. E.
Published: May 2008

Zygotene and pachytene spermatocytes from Massey I (t1 5;26) and Massey II (t2 8;11) translocation heterozygotes each contained one trivalent, often delayed in pairing, while cells from double Massey translocation heterozygotes had two such trivalents. As meiosis progressed, trivalents became fully paired, with acrocentric axes in a cis configuration. Abnormal pairing configurations often resulted from interactions between unpaired chromosome axes or segments. However, when two Massey trivalents were present in the same nucleus, there was no pairing interaction between them. In different Massey translocation heterozygotes, trivalent-involved pairing abnormalities occurred in 14–28% of cells, with XY–trivalent and XY–bivalent–trivalent associations being as high as 7.1–23.1%. In spermatocytes from single and double Massey translocation heterozygotes with normal-sized testes, the total SC abnormality frequency was 34.4% for the t1 heterozygotes, 27.1% for the t2 heterozygotes, and 21.4% for the double heterozygote. One Massey II heterozygote with one normal and one small testis had significantly higher SC abnormality frequency (54%) than normal rams. A trisomic cell was recorded in one ram and two hyperdiploid cells in another ram, but these were unrelated to the translocations. It is suggested that resolution of pairing abnormalities by synaptic adjustment is important in reducing the effects on fertility of the translocations.Key words: sheep, Robertsonian translocation, trivalent, abnormal pairing configuration.
Highly repetitive sequences in B chromosomes of Secale cereale revealed by fluorescence in situ hybridization
Authors: Cuadrado Angeles , Jouve Nicolas
Published: May 2008

An analysis of the presence and distribution of the rye and wheat repeated sequences in rye B chromosomes was carried out by fluorescent in situ hybridization. Probes used consisted of three highly repetitive sequences from rye (pSc119.2, pSc74, and pSc34) and the multigene families for the 25S–5.8S–18S and 5S rDNA from wheat (pTa71 and pTa794, respectively). pSc74 and pSc119.2 showed hybridization signals in the telomeric regions of rye B chromosomes. The remaining DNA clones did not hybridize to the B chromosomes.Key words: Secale cereale, rye, repetitive DNA, fluorescence in situ hybridization, B chromosomes.
Detection of ribosomal DNA sites in lentil and chickpea by fluorescent in situ hybridization
Authors: Abbo S. , Miller T. E. , Reader S. M. , Dunford R. P. , King I. P.
Published: May 2008

Hybridization sites of an rDNA probe coding for the 18S, 5.8S, and 26S genes were detected on lentil and chickpea somatic chromosomes using fluorescent in situ hybridization. One pair of hybridization sites was detected in cultivated lentil Lens culinaris L. and wild lentil L. orientalis (Boiss.) Hand.-Mazz., and in both the hybridization sites of the ribosomal probe correspond to the secondary constriction. In cultivated chickpea Cicer arietinum three pairs of rDNA sites were detected and in the wild C. reticulatum two pairs were detected. The karyotypic relationship between the cultivated C. arietinum and its wild progenitor C. reticulatum is discussed.Key words: chickpea, lentil, rDNA sites, nucleolus organizer region, fluorescent in situ hybridization, primer-mediated in situ hybridization.
In pursuit of a molecular mechanism for adaptive mutation
Authors: Rosenberg Susan M.
Published: May 2008

An unexpected way of making mutations in bacteria has challenged concepts of the genetic mechanisms behind evolution for the past 6 years. Work on the molecular mechanism of these so called "adaptive" mutations is rapidly revealing a surprising and novel molecular mechanism, and it is altering our understanding of how mutations form in nondividing cells.Key words: adaptive mutations, bacteria, genetic recombination, RecA, RecBCD, evolution.
Genetic polymorphism between and within Meloidogyne species detected with RAPD markers
Authors: Castagnone-Sereno Philippe , Vanlerberghe-Masutti Flavie , Leroy Frederic
Published: May 2008

Genetic analyses were conducted on root-knot nematode populations belonging to the four major species of the genus Meloidogyne and originating from many countries throughout the world. Discrete genetic markers used in this study were random genomic DNA sequences amplified by the polymerase chain reaction (RAPD). Primers of 17–30 nucleotides with 30–55% G + C content were tested. Five of them generated a total of 74 scorable markers that provided reliable polymorphisms both between and within species. Using RAPD patterns alone or in combination, all the Meloidogyne species and populations studied could be unambiguously discriminated. Based on the presence or absence of bands, maximum-parsimony analysis of the data resulted in clustering of species and populations congruent with previous isoenzymatic and molecular data. The resulting tree confirmed the early divergence of M. hapla from the other species and also that M. arenaria is closer to M. javanica than it is to M. incognita. The bootstrap analysis significantly supported most of the specific branching observed in the topology but did not identify the three M. arenaria populations as a monophyletic group.Key words: Meloidogyne spp., parsimony, phylogenetic analysis, RAPD.
Cytotaxonomic differentiation of the Afrotropical Drosophila montium subgroup: D. diplacantha and D. seguyi. The major role of reverse tandem duplications
Authors: Mavragani-Tsipidou P. , Zambetaki A. , Kleanthous K. , Pangou E. , Scouras Z. G.
Published: May 2008

Aiming to establish phylogenetic relationships among species of the montium subgroup, detailed polytene chromosome maps are given showing intraspecific polymorphism and ecdysone induced larval puffing pattern profiles of two Afrotropical members of this subgroup, Drosophila diplacantha and D. seguyi. Both species exhibit two unique characteristics that define the montium subgroup, namely, a large number of reverse tandem duplications and a progressive darkening of anterior spiracles of the late third instar larvae, which is accompanied by a definite temporal and spatial puffing pattern of the salivary gland chromosomes. In contrast with the well-formed Balbiani ring 1 (BR1) observed in Oriental and Indian montium species, BR1 exhibits a different developmental profile in D. diplacantha, while it is obscured in D. seguyi. Although phyletic comparisons of five species from five different complexes within the subgroup show some conservation in banding and puffing pattern homologies, an analysis to assign map sections by sequential rearrangements remains unresolved at this time. The evolution of the subgroup is discussed in relation with the sharing of reverse tandem duplications, especially those including the montium BRs.Key words: Drosophila montium, polytene chromosomes, Balbiani rings, puffs, duplications, inversions.
A mid-arm interchange as a potential reproductive isolating mechanism in the medically important Simulium neavei group (Diptera: Simuliidae)
Authors: Procunier William S. , Muro Abraham I.
Published: May 2008

The Simulium neavei group is medically important as a vector of human onchocerciasis and is unique among blackflies because of the attachment to freshwater crabs during parts of the larval and pupal life cycle stages. Detailed larval salivary gland polytene chromosome maps are presented for two taxa designated S. neavei Amani form A and S. neavei Amani form B, which are probably synonymous with the previously described morphospecies, S. nyasalandicum and S. woodi, respectively. Simulium neavei Amani form B differs from S. neavei Amani form A by three paracentric inversions, a large deletion and a chromocentre, while the latter taxon differs from the former one by a mid-arm interchange. The fixed mid-arm interchange (1 – tr) between two related taxa is unique among the Simuliidae. Detailed banding analysis of S. neavei Amani form B shows that, relative to S. neavei Amani form A, sections 16a, 16b, and 17c of the short arm of chromosome one (IS) have been inserted into section 69/70 of the short arm of chromosome three (IIIS). Assignment of directionality for this interchange is inferred because of the near universality in the Simuliidae of a chromosome III long arm to short arm ratio of 2:1. We propose that the mid-arm interchange acted as a primary isolating mechanism because of the segregational load on F1 heterozygous interchange progeny. The magnitude of the segregational load would be dependent on the frequency of pairing and crossing-over between the transposed interstitial segment and its original counterpart in the chromosome complement. Nonpairing in the transposed region and normal random segregation would presumably lead to a 50% of gametes carrying the duplicated or deficient transposed segment, resulting in a segregation load of 50%. However, crossing-over in the paired interstitial region may greatly increase segregational load as result of multivalent formation at metaphase one (MI) and the generation of dicentric bridge(s) and acentric fragment(s) upon cell division. Such meiotic disjunction irregularities could lead to meiotic arrest, gametic loss and (or) cell restitution, and the eventual formation of polyploid (lethal) zygotes.Key words: mid-arm interchange, speciation, Simulium neavei group, cytotaxonomy, vector biology.
The molecular diversity of the 5S rRNA gene in barley (Hordeum vulgare)
Authors: Baum Bernard R. , Johnson D. A.
Published: May 2008

The 5S rDNA genes from several accessions of cultivated barley, Hordeum vulgare L., were amplified by the polymerase chain reaction, cloned, and sequenced. Analysis of the aligned sequences, followed by principal coordinate analysis, support the recognition of at least two distinct classes of 5S rDNA genes. The short repeat class corresponds to the 300-bp tandem repeat defined by E.V. Ananiev as containing several TAG repeating units. The long repeat class contains long tandem repeats and lacks the TAG repeating unit. Sequences in each class can be further subdivided, with the long repeat class containing two groups and the short repeat class containing two and possibly three groups. These results suggest that in cultivated barley the sequence diversity found within the 5S rDNA non-transcribed spacer region may be encoded by three or more loci and may be useful for phylogenetic analyses provided that orthology can be established.Key words: 5S rDNA, sequence diversity, barley, phylogenetic analysis.
Detection of rRNA and phaseolin genes on polytene chromosomes of Phaseolus coccineus by fluorescence in situ hybridization after pepsin pretreatment
Authors: Nenno M. , Schumann K. , Nagl W.
Published: May 2008

This is the first report of fluorescence in situ hybridization (FISH) on plant polytene chromosomes. Different protease pretreatments have been tested to improve fluorescence in situ hybridization FISH on polytene chromosomes of a plant, Phaseolus coccineus, with the aim to enable the detection of low-copy genes. The structural preservation of the chromosomes and the distinctness of the FISH signals were comparatively analysed with a probe for the ribosomal RNA genes after digestion with pepsin and trypsin. The pepsin pretreatment resulted in a general loosening of chromatin with good conservation of chromosome morphology and an increased number and density of signal points. The six nucleolus organizers exhibited significant differences in condensation. The pretreatment with pepsin enabled the detection of the low-copy genes encoding the seed storage protein phaseolin.Key words: plant, Leguminosae, ribosomal RNA genes, seed storage protein genes, protease.
Homology of p53 intronic sequences between four laboratory mouse strains and Japanese wild mouse (Mus musculus molossinus Mishima)
Authors: Tokumitsu Masayuki , Ogawa Katsuhiro
Published: May 2008

Strain variation in the mouse p53 gene sequences was investigated in various regions of the gene in 14 inbred strains of laboratory mice and one Japanese wild mouse strain (Mus musculus molossinus Mishima, M. MOL-MSM). Nucleotides within p53 introns 1 and 7, found to be identical in 10 of the laboratory strains (129/J, A/J, AKR/J, BALB/cJ, C3H/HeJ, C57BL/6J, CBA/J, CE/J, NZB, and SWR/J), were substituted for other nucleotide sequences in common with M. MOL-MSM and the four other strains (DBA/1J, DBA/2J, I/LnJ, and P/J). The latter were documented to have originated from a common ancestor. These observations thus suggested the possibility that the p53 gene may have become substituted by outcrossing of this ancestral strain with Asian mice; this is presumably related to the documentation that Japanese mice brought to western countries were used as laboratory mice early in this century. To establish p53 gene heterozygosity, female C3H/HeJ and male DBA/2J mice were mated to produce F1, hybrids (C3D2F1,). Electrophoresis of PCR fragments including polymorphic regions with or without restriction enzyme digestion, allowed clear distinction of paternal and maternal p53 alleles. These markers, therefore, should be useful for studying the loss of heterozygosity of the p53 gene during the carcinogenic process.Key words: p53 gene, polymorphism, Japanese wild mice, laboratory mice, loss of heterozygosity.
Some evidence of incipient speciation in Drosophila kikkawai
Authors: Gupta J. P. , Sundaran A. K.
Published: May 2008

Altogether 11 geographic populations of Drosophila kikkawai were analysed from the viewpoint of karyotypic variation, inversion polymorphism and sexual isolation. The results revealed that of all the populations, the New Guinea population was the most genetically diverged, characterized by its distinct karyotype, possession of a fixed inversion, and its females exhibiting sexual isolation at the level of preferential mating. Based on these findings it was inferred that incipient speciation has proceeded in D. kikkawai and its New Guinea population is on its way to speciation.Key words: Drosophila kikkawai, karyotype, fixed inversion, sexual isolation, incipient speciation.
Direct and sensitive fluorescence in situ hybridization of 45S rDNA on tomato chromosomes
Authors: Xu Jie , Earle E. D.
Published: May 2008

We describe a direct and sensitive fluorescence in situ hybridization protocol for plant chromosomes. We labelled 45S rDNA with fluorescein-12-dUTP and hybridized to somatic chromosomes of four tomato genotypes. This technique does not require posthybridization immunocytochemical amplifications. The improved signal sensitivity with this technique allowed identification of new rDNA loci on three pairs of chromosomes, in addition to the previously known locus on chromosome 2. We discuss favorable features of direct fluorescence in situ hybridization for chromosomes fixed on a slide and chromosomes or cells in suspension.Key words: direct fluorescence in situ hybridization, 45S rDNA, tomato chromosomes.
BamHI andHindIII repetitive DNA families in the rice genome
Authors: Mawal Yogesh , Moon Eunpyo , Chang Sandra , Wu Ray , Lagu Meena , Gupta Vidya , Ranjekar Prabhakar , Lagu Meena , Wu Ray , Moon Eunpyo , Chung Mei-Chu , Wu Hsin-Kan
Published: May 2008

In this paper we describe a novel method of cloning representative members of different repetitive DNA families based on the screening of a rice (Oryza sativa) genomic library using DNA from different C0t fractions as probes. Two genomic clones, which represent two different repetitive DNA families in rice, were isolated by this method and have been characterized. Their nucleotide sequences, copy numbers, distributions in major rice genome types, methylation patterns, and chromosomal localizations were determined.Key words: repetitive DNA, rice genome, Oryza.
A transcript family from a long-range repeat cluster of the house mouse
Authors: Weichenhan Dieter , Kunze Bärbel , Plass Christoph , Hellwig Thomas , Winking Heinz , Traut Walther
Published: May 2008

A family of closely related genes is a component of the polymorphic long-range repeat cluster D1Lub1 of the house mouse. Members of the gene family have diverged from one another by rearrangements and point mutations. D1Lub1 clusters have low (≈50) or high (≥500) copy numbers. In mice with high-copy clusters five or six poly(A)+ RNAs are found, while in mice with low-copy clusters only a single member of the RNA family is detected. The RNA family is synthesized in a tissue-independent manner. Each member of the RNA family is defined by a set of DNA probes. Cross hybridization with the probes reveals common 5′ regions and variable remaining parts. The RNA variants are probably transcribed from different gene copies.Key words: long-range repeat cluster, long-range repeat derived gene family, mRNA family.