bluuebunny/crossref_metadata_2025 huggingface dataset:
Retrotransposon-microsatellite amplified polymorphism (REMAP) markers for genetic diversity assessment of the rice blast pathogen (Magnaporthe grisea)
Authors: Chadha Sonia , Gopalakrishna T
Published: April 2011

This present study is the first report of the application of the retrotransposon-microsatellite amplified polymorphism (REMAP) technique in fungi. Genome fingerprinting has a major role in the characterization of population structure and in the analysis of the variability in fungi. Retrotransposon-microsatellite amplified polymorphism assay was used in virulent isolates of a rice blast pathogen (Magnaporthe grisea) as a new assay system for genetic variability studies that overcomes the limitations of previous techniques. The high polymorphism observed in REMAP could be due to past or recent actions of retrotransposon in M. grisea. Retrotransposon-microsatellite amplified polymorphism, with its superior marker utility, was concluded to be the marker of choice for characterizing M. grisea isolates.Key words: Retrotransposon-microsatellite amplified polymorphism (REMAP), MAGGY, rice blast, Magnaporthe grisea, genetic diversity, retrotransposons.
Meiotic stability of B chromosomes and production of macrospermatids in Aiolopus strepens (Orthoptera: Acrididae)
Authors: Suja J. A. , Vega C. Garcia de la , Rufas J. S.
Published: April 2011

Four males from several Spanish natural populations of Aiolopus strepens were found to carry B chromosomes. These are short and acrocentric and are identical in the different individuals. They show mitotic instability and meiotic stability. When present in odd numbers one unpaired B is generally observed, while in even numbers they usually form bivalents. In no case were lagging B's observed. B chromosomes do not affect nucleolar expression. A significant increase in the number of macrospermatids is found in individuals with B's. This is more pronounced in follicles containing odd numbers of supernumerary chromosomes. A possible explanation based on an assumed influence of B univalents on the maintenance of intercellular connections is discussed.

Key words: B chromosomes, spermiogenesis, insect cytogenetics.
Polysomy and supernumerary chromosomes in Ornithogalum umbellatum L. (Liliaceae)
Authors: Rejón C. Ruiz , Lozano R. , Rejón M. Ruiz
Published: April 2011

One hundred bulbs of Ornithogalum umbellatum L. have been analyzed cytogenetically in one natural population collected from the Sierra Nevada of Spain. Three types of plants were identified: (i) diploid plants (2n = 18, 26%); (ii) diploid plants with a variable number of B chromosomes (1–8 B's, 40%); and (iii) polysomic plants (2n = 19–23) with or without B's (34%). B's are of two types: metacentric and acrocentric and are associated with three types of abnormalities: (i) failure of the A chromosomes to move to the poles at anaphase I; (ii) nondisjunction of some A chromosomes at anaphase II; and (iii) the occurrence of tetraploid sporocytes. The B's are isopycnotic, do not associate with the A's, and invariably occur as univalents at first meiosis but show no tendency for elimination. All members of the complement except the satellite chromosome, no. 6, have been detected in a trisomic or a tetrasomic condition. Additionally some unusual structural variants, not present in the diploid standard complement, appear in some polysomic individuals. The polysomic elements are euchromatic, stable, and they do not associate either with normal chromosomes or with B's. The polysomic elements form univalents when they are trisomic and bivalents when tetrasomic. The fact that a high frequency (94%) of the polysomic elements also carry B's suggests that these two forms of numerical variation are interrelated in origin.

Key words: Ornithogalum umbellatum, polysomy, supernumerary chromosomes.
Chromosomal localization of the white gene of Lucilia cuprina (Diptera; Calliphoridae) by in situ hybridization
Authors: Bedo D. G. , Howells A. J.
Published: April 2011

The white gene of Lucilia cuprina was mapped to trichogen polytene chromosomes using in situ hybridization. A tritium-labelled riboprobe made from the first gene cloned from this species was used with techniques modified from standard methods used for Drosophila melanogaster. Cytological data limiting the location of the white gene to a small portion of 3L and complementing the in situ results are also presented.

Key words: Lucilia cuprina, white gene, in situ hybridization.
Genetic analysis of cold hardiness and dormancy in alfalfa
Authors: Perry M. C. , McIntosh M. S. , Wiebold W. J. , Welterlen Mark
Published: April 2011

Cold hardiness and fall dormancy in alfalfa (Medicago sativa L.) are positively associated, although this relationship is not always desirable for maximum production. The purpose of this study was to determine basic genetic information about cold hardiness and dormancy utilizing six parents differing in their cold hardiness and fall dormancy and their S0 and S1 progeny. A 6 × 6 diallel analysis was conducted to determine differences in general and specific combining abilities. Parent–offspring regression analyses were used to estimate heritabilities for cold hardiness and fall dormancy. Fall dormancy was measured as plant height 42 days after a final cut in September. Cold hardiness was measured using specific conductivity of exosmolyzed electrolytes of plant root tissues subjected to −8 °C. General combining abilities were significant for specific conductivity and height. Specific combining ability was also significant for specific conductivity. Mean values for S0 cross progeny were 11 to 13% higher than midparent values. Heritability estimates based on parent–offspring regression coefficients were 1.32 for specific conductivity and 0.72 for height.Significant positive phenotypic correlations were found for specific conductivity and fall growth for all generations except for height for S1 progeny. The correlations decreased with each successive generation. Genotypic correlations were positive, large, and increasing for each generation indicating large, negative, and decreasing environmental correlations. Linkage of these two traits is suggested. Selection for cold hardiness and fall growth would be rapid with proper breeding methods, but selection for high levels of both cold hardiness and fall growth would be difficult with the cultivars used in this study.

Key words: cold hardiness, dormancy, alfalfa, Medicago sativa, conductivity, fall growth, phenotypic, genotypic.
Morphology and genome analyses of interspecific hybrids of Elymus scabrus
Authors: Torabinejad J. , Carman J. G. , Crane C. F.
Published: April 2011

Sexual, hexaploid (2n = 42) Elymus scabrus (R. Br.) A. Löve (formerly Agropyron scabrum (R. Br.) Beauv.) was used as the male parent for crossability studies and genome analysis of this Australian species. Mean number of paired chromosome arms (PA) and mean number of chromosome associations per metaphase I cell were determined for four different interspecific hybrids. Means by the female parent of each interspecific hybrid were as follows: tetraploid Elymus canadensis L., 1.17 PA and 32.76 I + 0.04 II (ring) + 1.08 II (rod) + 0.005 IV (chain) in 179 cells from four F1's; hexaploid Elymus tsukushiensis Honda, 14.13 PA and 23.48 I + 4.69 II (ring) + 4.13 II (rod) + 0.27 III + 0.01 IV (ring) + 0.01 IV (rod) in 140 cells from three F1's; tetraploid Elymus longearistatus (Boiss.) Tzvelev, 4.20 PA and 27.53 I + 0.39 II (ring) + 3.12 II (rod) + 0.15 III in 59 cells from one F1; and tetraploid Elymus semicostatus (Nees ex Steud.) A. Löve, 3.98 PA and 27.961 + 0.34 II (ring) + 2.86 II (rod) + 0.16 III + 0.04 IV (chain) in 50 cells from one F1. All F1's were completely sterile. An amphiploid of F1 E. tsukushiensis – E. scabrus was obtained by 0.1% colchicine treatment. It was partially sterile and had the expected chromosome number of 2n = ca. 84. The data were interpreted to indicate that E. scabrus lacks the S and H genomes of E. canadensis, contains the Y genome and a modification of another genome of E. tsukushiensis, and a modification of the Y genomes of E. longearistatus and E. semicostatus. These results contradict a previous report of an S and H genome composition for the Australasian wheatgrasses.

Key words: apomixis, Elymus canadensis, Elymus longearistatus, Elymus semicostatus, Elymus tsukushiensis.
Differential zygotic abortion in an interspecific Lycopersicon cross
Authors: Gadish I. , Zamir D.
Published: April 2011

Monogenic segregations of seven isozyme markers were analyzed in F2 and reciprocal backcross progenies of an interspecific hybrid between Lycopersicon esculentum and L. pennellii (LA 716). In the F2 population, four markers, which map to three different chromosomes, deviated significantly from the expected Mendelian ratios and in all cases an excess of the L. pennellii alleles was observed. In the backcrosses all the genes segregated normally. These results and the lack of effect of different gametophytic selection conditions on the deviations indicated that the elimination of L. esculentum alleles in the F2 did not occur at prezygotic stages. Three of the isozymes were assayed in mature F2 seed and revealed similar deviations to those observed in F2 plants. These findings, as well as the lower numbers of seed per fruit observed in the F2 than in the backcross (where the hybrid functioned as female parent), indicate that differential zygotic abortion is the main cause of the unequal segregations. In addition, analysis of two linkage groups in the reciprocal backcrosses revealed higher recombination frequencies on the female side.

Key words: Lycopersicon esculentum, L. pennellii, unequal segregations, differential zygotic abortion, recombination.
Hybrid dysgenesis in Drosophila melanogaster: the elimination of P elements through repeated backcrossing to an M-type strain
Authors: Good Allen G. , Hickey Donal A.
Published: April 2011

The rapid increase in the frequency of P elements in natural populations of Drosophila melanogaster has led to the suggestion that these elements can spread in nature through replicative transposition. In an attempt to model the introduction of a small number of P flies into an M population we backcrossed P flies and their offspring to M flies. Two components of dysgenesis, P element activity and P element copy number (measured by DNA hybridization), were monitored each generation. In these experiments P elements were not capable of spreading rapidly enough to maintain 30–50 copies per fly and were rapidly lost from the population. We also found that the reduction in a fly's ability to induce gonadal dysgenesis was matched by an equivalent reduction in P element copy number as measured by DNA hybridization. These results are discussed in terms of the conventional mechanisms of selection or segregation; the conclusion is that there are conditions under which P elements can be lost from a population.

Key words: hybrid dysgenesis, P element, transposable elements, Drosophila.
Isolation and characterization of DNA probes from the short arm of the human X chromosome that detect restriction fragment length polymorphisms
Authors: Starr Terence , Wood Stephen
Published: April 2011

We have isolated 30 X chromosome specific probes from a flow-sorted library enriched for the human X chromosome. Hybridization to somatic cell hybrids containing different regions of the X chromosome localized nine of these probes to Xp. After testing 185 probe–enzyme combinations, three of the Xp probes were found to detect restriction fragment length polymorphisms.

Key words: DNA probe, polymorphisms (restriction), X chromosome.
Nuclear DNA content in the Australian Bulbine (Liliaceae)
Authors: Watson E. M.
Published: April 2011

Nuclear DNA measurements for 17 Australian populations of Bulbine support the recognition of the four major groups already suggested by chromosome studies. Within the perennial group, Bulbine bulbosa s. lat., the tuberless, 46-chromosome (hypo-8x) "rock lily" has a similar DNA content to the hypo-4x, 24-chromosome populations of the "bulbosa" complex, which has populations at hypo-4x, -8x, and -12x levels. The "rock lily" also has substantially less DNA than another 46-chromosome entity, represented by the Kroombit population. Within the annual group, Bulbine semibarbata s. lat., the distinctions are less clear. However, the winged-seeded, 4x, 28-chromosome "alata" appears to have slightly more DNA than the closely related 26-chromosome "semibarbata." The 54-chromosome, 8x annual populations of eastern Australia have a DNA amount consistent with their proposed allopolyploid origin. The 52-chromosome "semibarbata" populations of Western Australia have, as expected, a lower DNA content than the 54-chromosome form and approximately twice the 4x "semibarbata" amount. It is suggested that some observed clinal variation in DNA content and an apparent DNA deficit in some of the higher polyploids of both perennial and annual groups may be attributable to climatic trends since the Miocene.

Key words: Liliaceae, Bulbine, DNA content, polyploids, genome evolution.
The orientation behaviour of multiple chromosome configurations in acridid grasshoppers
Authors: John B.
Published: April 2011

The existing data on the behaviour of multiple chromosome configurations arising from single interchanges between either metacentric–telocentric or telocentric–telocentric nonhomologues in 10 species of acridid grasshoppers are compared with data from four new cases. Two of these new cases involve metacentric–telocentric exchanges but the other two, for the first time in acridids, deal with a reciprocal translocation between two nonhomologous metacentrics. The combined data are used to evaluate the factors that influence multiple orientation in this family of grasshoppers and reemphasize the importance of chiasma frequency and chiasma distribution for multiple behaviour. This conclusion is reinforced by a consideration of the known cases of chain of three multiples originating from the Robertsonian fusion of nonhomologous telocentrics in acridoids.

Key words: acridid grasshoppers, multiple chromosome configurations, chiasma distribution, orientation behaviour.
Trigenomic combinations for the analysis of meiotic control in the cultivated Brassica species
Authors: Busso C. , Attia T. , Röbbelen G.
Published: April 2011

Haploid hybrids of either Brassica campestris (AA) or B. oleracea (CC) with B. nigra (BB) show a relatively low amount of chromosome pairing as compared with the level observed in the hybrid B. campestris × B. oleracea. This finding led to assume that B. nigra may carry a genic system suppressing homoeologous pairing in Brassica. To test this hypothesis, trigenomic hybrids (genome constitution ABC, 2n = 27) were synthesized, in which the effect of the B genome on the homoeologous pairing of the A and C genomes could be measured. The results indicate the inability of B. nigra to affect the level of pairing between homoeologous chromosomes of the A and C genomes. No genetic factor for a suppression of pairing was found in the B genome and there were no cytoplasmic effects on the regulation of pairing. However, cytological evidence pointed to chances of a successful transfer of economically valuable genes from B. nigra into the A and C genomes through the normal events of meiotic recombination.

Key words: Brassica, triploid (trigenomic), homoeologous pairing, gene transfer.
Cytological mechanisms of thelytokous parthenogenesis in insects
Authors: Lamb Richard Y. , Willey Robert B.
Published: April 2011

The eight female parthenogenetic mechanisms recognized in insects are organized under the broad categories "ploidy restoration" and "ploidy stasis." Each term replaces three imprecise and inappropriate existing names. Of the eight mechanisms, two are given names for the first time, and a table brings together all mechanisms in a new manner that shows the exact point in meiosis during which the DNA is doubled.

Key words: insect reproduction, parthenogenesis, parthenogenetic mechanisms.
Inheritance and linkage of isozymes in Populus tremuloides (Michx.)
Authors: Hyun Jung O. , Rajora Om P. , Zsuffa Louis
Published: April 2011

Progenies of four controlled crosses were assayed electrophoretically to determine the inheritance of isozymes of 10 loci coding for six enzymes, aconitase (ACO), glutamate oxaloacetate transaminase (GOT), isocitrate dehydrogenase (IDH), phosphoglucomutase (PGM), 6-phosphogluconate dehydrogenase (6-PGD), and phosphoglucose isomerase (PGI), in roots of Populus tremuloides. Chi-square goodness of fit tests verified a single-gene Mendelian control of the segregating allozyme variants at each of five loci: Aco-1, Got, Pgm-2, 6-Pgd-2, and Pgi-2. Evidence was also obtained for a single-gene control of each of the remaining five loci (Aco-2, Idh, Pgm-1, 6-Pgd-1, and Pgi-1). ACO and PGM showed monomeric, while GOT, IDH, 6-PGD, and PGI had dimeric, banding patterns. The results of joint two-locus segregation tests indicated no linkage between 6-Pgd-2 and Pgi-2.

Key words: Populus species, electrophoresis, allozymes, inheritance, linkage.
Character association analysis in common wheat (Triticum aestivum L.)
Authors: Balyan H. S. , Singh Tejbir
Published: April 2011

Grain yield of wheat as a component characteristic of total dry matter (biological) yield is governed by harvest index (V. P. Kulshrestha and H. K. Jain. 1982. Z. Pflanzenzuecht. 89: 19–30). At the phenotypic level, both the grain and biological yields are dependent upon a number of measurable agronomic characteristics such as plant height, tiller number, spike length, and grains per spike, etc. From a breeder's point of view, it is of great value to know the relative significance of these characteristics in determining grain yield to design appropriate selection strategies. The present study evaluated the covariability of yield in relation to various agronomic traits and ascertained their direct and indirect contributions towards grain yield.

Key words: wheat, grain yield.
The chromosomal location of a gene (msg) affecting megasporogenesis in durum wheat
Authors: Joppa L. R. , Williams N. D. , Maan S. S.
Published: April 2011

An aneuploid durum wheat line (Triticum turgidum L. var. durum) having 13 chromosome pairs and 2 unpaired chromosomes at metaphase I of meiosis in pollen mother cells (i.e., monosomic for chromosomes 7A and 7D) was observed to produce some progeny plants with 2n = 40 chromosomes. These aneuploid (triploid) plants were usually weak and sterile. Triploid plants also occurred in the progeny of durum plants monosomic for chromosome 7A, or in progeny of plants that were mono-telodisomic or ditelomonotelosomic for chromosome 7Aq (13 II + 1 t II or 13 II + t II + t I) but not in the progeny of plants ditelomonotelosomic for chromosome 7Ap (13 II + t II + t 1). Therefore, there is a gene(s) on chromosome arm 7Ap that prevents the production of diploid (2n) egg cells in wheat. In the absence of 7Ap, a portion of the egg cells have 26 chromosomes, which when fertilized with a pollen nucleus with 14 chromosomes, produces progeny plants with 2n = 40 chromosomes. The data also indicated that chromosome arm 7Dp probably contains a second gene that is capable of preventing the production of triploid plants.

Key words: Triticum turgidum L. var. durum, polyploidy, aneuploid, triploid, monosomic.
Doubled haploids for detecting pleiotropy and linkage of genes controlling two characters
Authors: Choo T. M. , Reinbergs E.
Published: April 2011

A new method was developed for detecting pleiotropy and linkage of genes controlling two characters. It employs doubled-haploid lines derived from diallel crosses and permits quantification of pleiotropic effects. The method was used to study genetic correlations between five pairs of four characters (heading date, plant height, the number of spikes per hill, and grain yield) in seven varieties of barley. Results suggested that pleiotropy was present in all five pairs of characters and linkage in four pairs of characters.

Key words: barley, haploids, pleiotropy, linkage.
In situ digestion of Drosophila virilis polytene chromosomes by AluI and HaeIII restriction endonucleases
Authors: Mezzanotte R. , Bianchi U. , Marchi A.
Published: April 2011

Polytene chromosomes of Drosophila virilis were treated with AluI and HaeIII restriction endonucleases. Both enzymes were capable of extensively digesting chromosomal DNA, with the exception of some regions that contain repetitive DNAs. Moreover, a comparison was made between our data and the data already obtained with the same enzymes in D. melanogaster. On this basis, AluI digestion showed that the 5S RNA genes of D. virilis and D. melanogaster have different base composition, while digestion with HaeIII revealed resistance of the histone genes in D. virilis, contrary to what was previously found in D. melanogaster.

Key words: restriction endonucleases, 5S RNA genes, histone genes, polytene chromosomes, Drosophila species.
Genetics and cytology of unreduced gametes in cultivated rye (Secale cereale L.)
Authors: Lelley T. , Mahmoud A. A. , Lein V.
Published: April 2011

An inbred genotype of cultivated rye was found that produces unreduced gametes in a very regular fashion. In the cross progeny of this line with another inbred line, which did not show unreduced gametes, the inheritance of this phenomenon was studied. The formation of unreduced gametes appears to be a recessive trait controlled by more than one gene. Chiasma frequency in 4n PMCs is exactly twice that in 2n PMCs. In first metaphase of 4n PMCs only bivalents (no multivalents) were seen. The possible mechanism leading to unreduced gametes and its evolutionary implications are discussed.

Key words: rye, unreduced gametes, polyploidy, genetic control, chiasma frequency.
Cross prediction in barley using doubled-haploid lines
Authors: Choo T. M.
Published: April 2011

The usefulness of the cross prediction method developed by J. L. Jinks and H. S. Pooni (1976, Heredity 36: 253–266) in a doubled-haploid breeding program was evaluated. Doubled-haploid lines were derived from two barley crosses by the bulbosum method. Doubled-haploid lines from each cross were divided into two sets, one with 52 lines and the other 58 to 79 lines. These doubled-haploid lines were evaluated for grain yield, heading date, and plant height in hill plots with 10 replications at Elora, Ontario, in 1973 and 1974. The mean and phenotypic variance of doubled-haploid lines from the first set were used to calculate the predicted distribution under the assumption of normality. The predicted distribution was compared with that observed from the other set by a χ2 test. It was found that the predicted distribution differed from the observed distribution in the majority of the cases and the two tails of the distribution accounted for much of the difference in 6 of the 12 (= 3 characters × 2 crosses × 2 years) cases. The numbers of transgressive lines and best lines were also predicted for the three characters in the two crosses in each year. Twenty of the 24 observed numbers of transgressive lines were not within their 95% confidence interval but 8 of the 12 observed numbers of best lines were within their 95% confidence interval. A significant correlation coefficient between predicted and observed numbers of transgressive lines was obtained for grain yield and heading date. The prediction that one cross had more high-yielding lines and fewer short-stature lines than the other cross agreed well with the actual observation. It appears that the cross prediction method is of value in predicting the cross potential and can be used for identifying superior crosses in a doubled-haploid breeding program in barley.Key words: barley, haploids, cross prediction.
The B chromosomes of Locusta migratoria. III. Effects on the activity of nucleolar organizer regions
Authors: Salcedo F. Javier , Viseras Esther , Camacho Juan Pedro M.
Published: April 2011

Active nucleolus organizing regions (NORs) have been studied in two controlled crosses in the locust Locusta migratoria. NOR activity was detected in all the chromosomes of the standard complement but not in the B chromosomes. On the basis of both the frequency with which they are active and the size of the resulting nucleolus, NORs in this species can be classified in three groups: (i) type I primary NORs that are active in the majority of cells and give rise to large nucleoli; (ii) type II primary NORs that are active in the majority of cells but produce small nucleoli; and (iii) secondary NORS that are active in a minority of cells and yield small nucleoli. The presence of B chromosomes influences the mean activity of some NORs, particularly those giving rise to small nucleoli (groups ii and iii), although different populations yield contradictory results. Our findings indicate that NOR activity in L. migratoria is regulated by genetic and environmental factors, and can be influenced by the presence of B chromosomes which tend to increase the cellular level of NOR activity. An analysis of dependence between NORs for activity demonstrated the existence of a positive dependence between many of the NORs that give rise to small nucleoli. The presence of B chromosomes, however, favoured these enhancement relationships between nonhomologous NORs.Key words: Locusta, B chromosomes, nucleolar organizer.
A method to induce Giemsa staining resistance of avian W chromosomes: detection of an additional W chromosome in a turkey
Authors: Mayr B. , Auer H.
Published: April 2011

A hypotonic treatment using a low osmolal solution (0.038 Os/kg) led to a poor staining of the W chromosome in all our investigated bird species (chicken, turkey, pheasant, goose, pigeon, bearded vulture, and barn owl). A turkey establishing a ZWW karyotype was detected.Key words: birds, W chromosome, differential Giemsa staining, ZWW karyotype.
Analyse génétique de la zone d'hybridation entre les deux sous-espèces de souris Mus musculus domesticus et Mus musculus musculus en Bulgarie
Authors: Vanlerberghe Flavie , Boursot Pierre , Catalan Josette , Gerasimov Svestoslav , Bonhomme François , Botev B. Atanassov , Thaler Louis
Published: April 2011

The hybrid zone between the two subspecies of mice Mus musculus domesticus and Mus musculus musculus, which has been studied extensively in Denmark, crosses Europe to the Black Sea through the Alps and the Balkans. Two hundred and seventy-nine animals were captured in 22 localities along a transect across the Balkans. The animals were characterized for seven diagnostic nuclear loci by protein electrophoresis and by restriction pattern analysis of their mitochondrial DNA. The nuclear data show a sharp transition between the two subspecies, most of the variations in allele frequencies (from 0.9 to 0.1) occurring within a 36-km section of the transect. The introgression varies from one locus to the other and is more pronounced, in terms of distance, in M. m. musculus territory. Mitochondrial DNA introgression is important but occurs in one direction only, i.e. from M. m. musculus to M. m. domesticus, while a cytoplasmic transfer from M. m. domesticus to M. m. musculus has been reported. A previous study showed that no Y chromosome introgression occurs. The different behaviour of these three types of markers could be due to the interaction between selection against hybrid genomes and meiotic recombination. Objectively, it would appear that the genes that can introgress are neutral or nearly so and have been separated from deleterious genes they were linked to by recombination. This could explain the differential introgression between autosomal loci. The mitochondrial and Y chromosomes undergo no or very little recombination and each is transmitted as a whole. Their degree of introgression is thus indicative of the intensity of selection resulting from the amount of functional differentiation between the two taxa, which seems to be strong for the Y chromosome and weak for mitochondrial DNA. We propose that the asymmetry of nuclear introgression is due to different population structures. As M. m. musculus is relatively less structured, the rapid spreading of introgressed genes would be favoured. Such a scheme, however, can hardly account for the unidirectionality of the mitochondrial flow, which could be due to sex-dependant behaviour.Key words: mice, hybrid zone, introgression, enzyme polymorphism.
Polysomaty and somatic reduction in Phaseolus coccineus L.
Authors: Cavallini A. , Cremonini R. , Cionini G. , Cionini P. G.
Published: April 2011

By means of karyological, cytophotometric, and autoradiographic analyses it has been shown that, owing to alterations in the DNA synthesis – mitosis sequence, cells with different nuclear conditions are continuously formed de novo and proliferate in Phaseolus coccineus meristems. Besides diploid cells, the following also occur: (i) polyploid cells as the result of chromosome endoreduplication followed by mitosis; (ii) haploid cells as the result of the separation of the two groups of homologous chromosomes in cells that have omitted DNA reduplication; and (iii) since haploid cells undergo chromosome endoreduplication and divide, isogenic cells can be produced. Diploid mitoses alone are present in the meristems of early embryos; haploid mitoses first appear in both root and shoot meristems with increasing embryo development, followed later by cells undergoing chromosome endoreduplication. The study of the root apex has shown that neither polyploid nor reduced cells occur with the same frequency in its various portions. These results are discussed in relation to pertinent data in the literature and the mechanisms responsible for the occurrence of polysomaty and somatic reduction are suggested.Key words: isogenic cells, Phaseolus coccineus, polysomaty, somatic reduction.
Genetic components of chromosome behaviour in Papaver somniferum L.
Authors: Patra N. K. , Chauhan S. P.
Published: April 2011

Three nuclear variables, namely chiasma frequency, internuclear variation of chiasmata, and numerical deviations in the chromosomes of pollen mother cells, referred to as meiotic lability, were studied in 5 × 5 diallel crosses of Papaver somniferum L. Chiasma frequency and meiotic lability were controlled by both additive and dominant gene actions and internuclear chiasmata variance was controlled by the dominant component. High values for chiasma frequency and meiotic lability were dominant over their low values, whereas low values of internuclear variation of chiasmta were dominant over the corresponding high values.Key words: chromosome behaviour, genetic components, Papaver somniferum.
Micronuclear DNA sequences from Tetrahymena do not confer mitotic stability on ARS plasmids in Saccharomyces
Authors: Horsfall Wendy H. , Pearlman Ronald E.
Published: April 2011

Genomic libraries containing micronuclear DNA sequences from Tetrahymena thermophila have been constructed in a vector containing ARS1, SUP11, and ura3 sequences from the yeast Saccharomyces cerevisiae. When transformed into a strain of S. cerevisiae carrying a suppressible ochre mutation in the ade2 gene, viable transformants are obtained only if the transforming plasmid is maintained at a copy number of one or two per cell. Mitotic segregation of the plasmid is easily assessed in a colour assay of transformants. Using this assay system, we showed that micronuclear DNA from Tetrahymena does not contain sequences that confer mitotic stability on yeast ARS-containing plasmids; i.e., sequences that function analogously to yeast centromere sequences. One transformant was analyzed that carries Tetrahymena sequences that maintain the copy number of the ARS plasmid at one or two per cell. However, these sequences do not confer mitotic stability on the transformants and they confer a phenotype in this assay similar to that of the REP3 gene of the yeast 2 μm plasmid.Key words: mitotic stability, centromere, Tetrahymena, Saccharomyces.
Maize (Zea mays L.) DNA sequences homologous to the oncogenes myb, ras, and src
Authors: Zabulionis R. B. , Atkinson B. G. , Procunier J. D. , Walden D. B.
Published: April 2011

The presence of genes that may govern cell division and differentiation is being investigated in the agronomically important higher plant Zea mays. Heterologous animal oncogene probes (v-myb, v-fos, v-src, and v-Ki-ras) were hybridized to Southern-blotted endonuclease-restricted fragments of maize DNA under conditions that allowed up to 28% mismatch between the probe and genomic sequence. Human, yeast, and Escherichia coli endonuclease restricted DNA served as controls for the hybridization conditions used. The Southern blotted DNAs were hybridized with probes to ribosomal DNA and pBR322 to ensure that the observed hybridization signals were not due to spurious binding or contamination of the oncogene probes. Maize DNA sequences homologous to v-myb, v-src, and v-Ki-ras were detected. No maize sequences homologous to the v-fos probe were detected. The oncogene probes did not detect any homologous sequences in E. coli DNA and all the reported homologous bands in human and yeast DNA were observed. These results illustrate the evolutionary conservation of animal proto-oncogenes within the plant kingdom, and suggest that these sequences may play a role in the replication and differentiation of plant cells.Key words: oncogenes, v-myb, v-fos, v-src, v-Ki-ras, Zea mays.
Inheritance of grain protein concentration, grain yield, and related traits in spring wheat (Triticum aestivum L.)
Authors: McKendry A. L. , McVetty P. B. E. , Evans L. E.
Published: April 2011

The inheritance of grain protein concentration (GPC), grain protein yield (GPY), total nitrogen at maturity (TNM), nitrogen harvest index (NHI), grain yield (GY), total dry matter (TDM), and harvest index (HI) were studied in two spring wheat crosses, 'HY521/UM684' and 'HY521/Sinton' in 1985 at Winnipeg and Portage la Prairie, Manitoba. Analysis of variance of parental performance by location indicated that the parents differed significantly for all traits measured and that genotype by location interactions accounted for less than 8% of the observed variation. Generation means analyses indicated that all traits were primarily under genetic control in both crosses with additive gene action being significant for all traits studied. Dominance gene action was detected for all traits but the degree and direction was both trait and genotype specific. Additive × additive epistasis was significant for GPY, TNM, GY, and TDM, but again, was genotype specific. Variance analyses indicated a large genetic component of the variation relative to the environmental component for all traits studied. F2 broad sense heritabilities were moderately high for GPC (0.57–0.76), GPY (0.57–0.76), TNM (0.56–0.73), NHI (0.39–0.59), GY (0.51–0.70), TDM (0.65–0.79) and HI (0.50–0.67). Narrow sense heritabilities were moderately high for GPC (0.50–0.75) and HI (0.49–0.58) but were somewhat lower for GPY (0.26–0.48), TNM (0.27–0.38), NHI (0.24–0.38), GY (0.27–0.39) and TDM (0.32–0.65). Implications of the results of this study on breeding for simultaneous improvement in GPC and GY are discussed.Key words: bread wheat, heritability, grain protein yield, total nitrogen at maturity, nitrogen harvest index, total dry matter, harvest index, breeding strategies.
Quadrivalent formation in a tetraploid chicken oocyte
Authors: Solari A. J. , Fechheimer N. S.
Published: April 2011

Synaptonemal complex analysis of an exceptional tetraploid oocyte from a diploid chicken heterozygous for the MN t (Z;1) rearrangement was performed by electron microscopy of a spread preparation. Ten separate quadrivalents (26% of the chromosomal axes) were analyzed, as well as 50 autosomal bivalents. All the axes less than 2.5 μm in length formed bivalents (38) only, while axes in the 2.5–4.2 μm range formed 5 quadrivalents and 12 bivalents. The longer, separate axes formed quadrivalents only. Partner switches in excess of one were documented. The two identical W chromosomes paired only at the ends of their short arms. Quadrivalent formation may require a threshold length (2.5 μm), at least in this species. The tip of the short arm of the W chromosome may be a pairing initiation point, and it corresponds to the region associated with a localized recombination nodule previously described in diploid oocytes.Key words: quadrivalent, tetraploid, synaptonemal complex, chicken oocyte.
Synaptonemal complex proteins
Authors: Heyting C. , Dietrich A. J. J. , Moens P. B. , Dettmers R. J. , Offenberg H. H. , Redeker E. J. W. , Vink A. C. G.
Published: April 2011

Synaptonemal complexes were isolated from rate spermatocytes for the purpose of biochemical and morphological analysis. Several monoclonal antibodies were elicited against purified synaptonemal complexes to study the composition and assembly of these structures. Four classes of antibodies could be discriminated according to the polypeptides that they recognize on Western blots of purified synaptonemal complexes, namely antibodies recognizing (i) a 190-kDa polypeptide; (ii) a 30- and a 33-kDa polypeptide; (iii) two polypeptides with molecular weights of about 120 kDa; and (iv) polypeptides with molecular weights of 66–55 kDa. The localization of these antigens within spermatocytes was analyzed light microscopically, by means of the immunoperoxidase technique and ultrastructurally, by immunogold labelling of surface-spread spermatocytes. The 66-to 55-kDa polypeptides are not confined to synaptonemal complexes; rather, these polypeptides appear to be chromosomal components. The 190-, 30-, and 33-kDa polypeptides make part of the lateral elements of paired as well as unpaired segments of synaptonemal complexes. The 120-kDa polypeptides were localized on the inner edge of the lateral elements, specifically in paired segments of synaptonemal complexes. The distribution of the 190-, 120-, 30-, and 33-kDa polypeptides within the testis was analyzed by immunofluorescence staining of cryostat sections. All these polypeptides turned out to be specific for nuclei of zygotene up to and including diplotene spermatocytes. Only in some early spermatids could the 190-, 30-, and 33-kDa polypeptides be detected, presumably in remnants of synaptonemal complexes. We conclude that the lateral elements of synaptonemal complexes do not arise by rearrangement of pre-existing components in the nucleus, but that their major components are newly synthesized during meiotic prophase.Key words: synaptonemal complex, immunocytochemistry, meiosis.
Population structure and evolutionary progress
Authors: Slatkin Montgomery
Published: April 2011

Wright's shifting-balance theory is discussed as an example of a process that can cause species to evolve combinations of characters that could not evolve under natural selection alone. A review of the existing theory of peak shifts indicates that the conditions of extreme isolation that are necessary to permit genetic drift to alter the outcome of natural selection in local populations would make gene flow too weak to spread a new combination of genes to other populations in a reasonable time. Instead, it seems likely that major demographic changes must occur in a species for the shifting-balance process to work. A discussion of direct and indirect studies of gene flow in natural populations suggests that the current genetic structure of many species is likely to reflect past demographic events rather than ongoing gene flow. It is possible then that demographic processes could be responsible for spreading new traits in a species, but that would be true whether those new traits evolved only owing to natural selection or owing in addition to genetic drift and other forces.Key words: shifting-balance theory, gene flow.
Intraspecific and interspecific genetic variation in Drosophila
Authors: Powell Jeffrey R. , Caccone Adalgisa
Published: April 2011

Utilizing the technique of DNA – DNA hybridization, we have characterized the degree of genetic variability in single-copy DNA both within and between several species of Drosophila. The results of intraspecific variation studies indicate considerable variation both for levels of nucleotide heterozygosity (estimated to be over 2%) as well as for insertions–deletions. Interspecific studies confirm this great deal of variability and further establish an extreme heterogeneity within Drosophila genomes for rates of divergence. This heterogeneity is much more extreme than that seen between exons and introns. The degree of single-copy DNA divergence generally supports phylogenetic affinities deduced from more traditional methods. However, exceptions occur where single-copy DNA divergence is not correlated with other properties such as degree of chromosomal differentiation, morphology, or ability to form interspecific hybrids. We argue that single-copy DNA divergence as measured by DNA–DNA hybridization is an accurate indicator of phylogenetic relationships and therefore sheds light on the evolution of other biological properties. Many, if not most, evolutionary tests require an accurate phylogeny of the group being studied and DNA, because of the high information content inherent within the molecule, offers the best hope of deriving true phylogenies.Key words: DNA evolution, Drosophila, molecular evolution, phylogenetics, DNA–DNA hybridization.
Molecular biology of enzyme adaptations in higher eukaryotes
Authors: Hickey Donal A. , Benkel Bernhard F. , Magoulas Charalambos
Published: April 2011

Multicellular eukaryotes have evolved complex homeostatic mechanisms that buffer the majority of their cells from direct interaction with the external environment. Thus, in these organisms long-term adaptations are generally achieved by modulating the developmental profile and tissue specificity of gene expression. Nevertheless, a subset of eukaryotic genes are still involved in direct responses to environmental fluctuations. It is the adaptative responses in the expression of these genes that buffers many other genes from direct environmental effects. Both microevolutionary and macroevolutionary patterns of change in the structure and regulation of such genes are illustrated by the sequences encoding α-amylases. The molecular biology and evolution of α-amylases in Drosophila and other higher eukaryotes are presented. The amylase system illustrates the effects of both long-term and short-term natural selection, acting on both the structural and regulatory components of a gene–enzyme system. This system offers an opportunity for linking evolutionary genetics to molecular biology, and it allows us to explore the relationship between short-term microevolutionary changes and long-term adaptations.Key words: gene regulation, molecular evolution, eukaryotes, Drosophila, amylase.
Transposable elements and fitness in Drosophila melanogaster
Authors: Mackay Trudy F. C.
Published: April 2011

Transposable elements constitute a significant fraction of the Drosophila melanogaster genome. The five families of moderately repeated transposable elements identified to date occupy dispersed and variable genomic locations, but have relatively constant copy numbers per individual. What effect to these elements have on the fitness of the individuals harboring them? Experimental evidence relating to this question is reviewed. The relevant data fall into two broad categories. The first involves the determination of the distribution of transposable elements in natural populations, by restriction mapping or in situ hybridization, and the comparison of the observed distribution with different theoretical expectations. The second approach is to study directly the effects of new transposable element-induced mutations on fitness. The P family of transposable elements is a particularly efficient mutagen, and the results of experiments in which initially P-free chromosomes are contaminated with P elements are discussed with regard to P-induced fitness mutations.Key words: transposable elements, Drosophila melanogaster, insertional mutagenesis, fitness, P element mutagenesis, hybrid dysgenesis.
Molecular phylogeny of the family of apes and humans
Authors: Goodman Morris , Koop Ben F. , Czelusniak John , Fitch David H. A. , Tagle Danilo A. , Slightom Jerry L.
Published: April 2011

The morphological picture of primate phylogeny has not unambiguously identified the nearest outgroup of Anthropoidea and has not resolved the branching pattern within Hominoidea. The molecular picture provides more resolution and clarifies the systematics of Hominoidea. Protein and DNA evidence divides Hominoidea into Hylobatidae (gibbons) and Hominidae, family Hominidae into Ponginae (orangutan) and Homininae, and subfamily Homininae into two tribes, one for Gorilla, and the other for Pan (chimpanzee) and Homo. Parsimony and maximum likelihood analyses, carried out on orthologous noncoding nucleotide sequences from primate β-globin gene clusters, provide significant evidence for the human-chimpanzee tribe and overwhelming evidence for the human-chimpanzee-gorilla clade. These analyses also indicate that the rate of molecular evolution became slower in hominoids than in other primates and mammals.Key words: primate phylogeny, gene clusters, nucleotide sequences.
Cellular and genetical aspects of interactions between hosts and fungal symbionts in mycorrhizae
Authors: Gianinazzi-Pearson Vivienne , Gianinazzi Silvio
Published: April 2011

Contact between appropriate mycorrhizal symbionts initiates a cascade of events that leads to modifications in the behaviour of both organisms at cell and tissue levels and the establishment of a functionally compatible relationship. Mechanisms that regulate the outcome of the symbiosis must involve a complex interchange of signals that triggers changes in genome expression in either symbiont. Analysis of symbiosis-specific proteins, interspecific grafting experiments, and the obtention of fungal and plant variants with phenotypes deficient for mycorrhiza formation provide information to help unravel the molecular and genetical puzzles of fungus–host interactions in mycorrhizal associations.Key words: mycorrhiza, cellular relations, host mutants, fungal strains, interspecific grafting.
Aging, evolution and individual health span: introduction
Authors: Cinader B.
Published: April 2011

The effect of autologous and environmental wear and tear on genes and gene products will be considered in systems renewed by self-replicating stem and precursor cells as well as in systems that do not have the capacity for self-renewal. Aging will be discussed in terms of speciation and in terms of health-span differences between individuals of the same species. The analysis of speciation involves early as well as late-acting genes. The intraspecies analysis is primarily concerned with the second half of life and thus is not affected by selective pressures. Analysis of individual aging is concerned with health span, qualified by identification of the particular system that is responsible for the limit of health span in subpopulations; it depends on a subset of allelic products of many genes and their relative functional capacity. The identification of such alleles can provide the starting point for reverse genetics. Results will be presented, which have been obtained by analysis of age-related events in inbred mice, where regulation, involved in degenerative disease of old age, can be studied in groups of individuals with a relatively constant genetic background. It should be possible to identify appropriate probes for degenerative diseases of old age that can be used for detection of corresponding human genes. Worldwide demographic changes have created the need for a new type of public health policy. To respond to this need, we should learn how to identify individuals at risk from degenerative diseases of old age and how to treat them preventively.Key words: evolution of aging – demographic changes, life-span – health span, chromosome fragility, muscular dystrophy, Sandhoff disease, end cell and aging, hibernation and life-span, degenerative diseases of old age.