bluuebunny/crossref_metadata_2025 huggingface dataset:
The chloroplast genome of plants: a unique origin
Authors: Ozeki Haruo , Umesono Kazuhiko , Inokuchi Hachiro , Kohchi Takayuki , Ohyama Kanji
Published: April 2011

Complete nucleotide sequences of chloroplast genomes are now available for two green plants: Marchantia polymorpha (a liverwort) and Nicotiana tabacum (tobacco). Although these two plant species are taxonomically very distant from one another, their deduced gene organization is remarkably similar. This implies that the chloroplast genomes in all land plants may have arisen from a unique ancestor. Including the unidentified open reading frames, we establish the number of distinct chloroplast genes at about 125, consisting of 4 species of ribosomal RNA genes, 30 or 31 species of transfer RNA genes, and about 90 protein genes. About half of these genes are concerned with the basic mechanisms of gene expression in the chloroplast, such as transcription and translation, and share many features with prokaryotic organisms. Complete sequence analysis revealed that each functional protein complex containing components encoded by the chloroplast genes also contains nuclear-encoded ones, as if some of the genes from each complex have "migrated" to the nucleus from a symbiotic prokaryote during the course of evolution. By this process, the basis of the present nuclear–chloroplast relationships had been established in very early times (300–400 million years ago) before the branching of Bryophytina and Tracheophytina. From this unified single origin the present-day chloroplast genomes in plants have evolved mainly by mutations in nucleotides and rearrangement of DNA, but rarely by changes in gene content.Key words: chloroplast genome, complete DNA sequence, gene organization, Marchantia polymorpha, Nicotiana tabacum, unified origin.
Selection in natural and experimental populations of Drosophila pseudoobscura
Authors: Anderson Wyatt W.
Published: April 2011

The inverted gene arrangements of Drosophila pseudoobscura were used by Th. Dobzhansky in pioneering analyses of natural selection. Recent experiments have shed light on the mechanisms of selection contributing to the balanced polymorphism for the gene arrangements. In experimental populations, both major components of fitness, viability and fertility, are frequency dependent, and rare genotypes often have a selective advantage. Viabilities are also density dependent. The frequency dependence and density dependence of the fitness components are not universal. Some karyotypes are strongly influenced by frequency or density, some are slightly influenced, and some do not appear to be influenced at all. The role of heterozygote advantage in the selection on the gene arrangements is not clear. It is probably one important element in the overall selection, but viability and fertility do not always show a heterozygote advantage. Viability and fertility components of selection seem to be about equally important in changing inversion frequencies. Male mating success is an important component of selection in natural populations, and in one population rare male karyotypes have been found to have a pronounced mating advantage.Key words: selection, selection components, Drosophila pseudoobscura, inversions.
Could natural selection account for molecular evolution and polymorphism?
Authors: Gillespie John H.
Published: April 2011

A model of molecular evolution is presented that is based on the combined action of natural selection, genetic drift, and mutation. The mathematical description of the model uses strong-selection, weak-mutation limits to approximate the dynamics of multidimensional diffusion processes with one dimensional Markov chains. This approach leads to a great simplification of the dynamics and provides a unified method for describing many different mechanisms of natural selection. In this paper two models are examined, one based on selection in a randomly fluctuating environment, the other on overdominance. Both models exhibit similar dynamics, with a rapid buildup phase that introduces new alleles into the population, followed by a relatively quiescent phase where new alleles may enter and leave the population at a low rate. If occasional extreme environmental changes occur that favor particular alleles, the resulting dynamics turn out to be in remarkable agreement with many of the observations on molecular evolution and polymorphism. Thus the model is at least as successful as the neutral theory in accounting for evolutionary events at the molecular level.Key words: molecular evolution, natural selection, neutral theory.
Expression of the nodulation and nitrogen fixation genes in Rhizobium meliloti during development
Authors: Shen San Chiun , Wang Shui Ping , Yu Guan Qiao , Zhu Jia Bi
Published: April 2011

Genes that specify nodulation (nod genes) are only active in the free-living rhizobia or in the nodule initiation state of rhizobia. As soon as the repression of nod genes occurs in the bacteroids of the nodule, nifA is induced, while ntrC is inactivated and thus the nifA-mediated nif/fix genes are turned on. Limitation of available oxygen brings about the induction of nifA, which reflects the actual status of nif/fix gene activities in symbiotic state of rhizobia. Oxygen thus appears to be a major symbiotic signal to the expression of bacteroid nif/fix genes. Mutation of nifA or shortage of nifA product in wild-type rhizobia caused by the inhibition of multicopy nifH/fixA promoters leads to an abnormal development of nodules and premature degradation of bacteroids in nodules.Key words: nitrogen fixation, nodulation, nif/fix regulation, nifA mutant.
Expression of the genes encoding hsp73, hsp18, and ubiquitin in radicles of heat-shocked maize seedlings
Authors: Atkinson Burr G. , Liu Ling , Goping Ing Swie , Walden David B.
Published: April 2011

Radicles of intact 5-day-old maize (cv. OH43) seedlings exposed to a rapid, short-term elevation (2 h) in environmental (25 to 42.5 °C) temperature exhibit new and (or) enhanced synthesis of a specific set of proteins, the so-called heat shock proteins (hsps), with molecular masses of 108 000, 89 000, 84 000, 76 000, 73 000, 30 000, 23 000, and 18 000. Continuous exposure of intact seedlings to this elevated temperature results in a depression in the synthesis of these hsps after 8 – 12 h and a shift in the pattern of the proteins synthesized to one that resembles those proteins synthesized by radicles from seedlings grown at 25 °C. The transient synthesis of hsp73 and the hsp18 family in radicles from seedlings exposed to, and maintained at, an elevated temperature correlates with the levels of hsp73 and hsp18 mRNAs associated with their polyribosomes. The heat shock induced accumulation of these hsp mRNAs occurs concomitantly with a fourfold increase in polyribosome-associated ubiquitin mRNAs. However, unlike the transient association of hsp73 and hsp18 mRNAs with polyribosomes in radicles from seedlings maintained at 42.5 °C (8 – 12 h), the level of uniquitin mRNAs associated with polyribosomes does not return to a steady-state control (25 °C) level for at least 24 h. The marked, rapid increase in the level of ubiquitin mRNAs associated with polyribosomes in radicles from heat-shocked seedlings provides the first evidence implicating ubiquitin as a heat shock protein of plants.Key words: heat Shock, heat shock proteins, ubiquitin, maize.
Sequential mutagenesis of a maize gene, using the transposable element Dissociation
Authors: Kermicle Jerry L. , Alleman Mary , Dellaporta Stephen L.
Published: April 2011

Forty unstable isolates of an R allele conferring strongly colored seed (R-sc:124) were established using a two-step procedure involving the Ac – Ds transposable element system. First, a series of full-color reversions to R-sc were isolated from two existing Ds mutable alleles, r-sc:m1 and r-sc:m3. Variegated kernels were then selected from large-scale testcrosses of the revenant strains (Ac still present) to establish new mutants. Four of the 9 R-sc revenants from r-sc:m3 gave no mutable alleles, whereas 5 produced a total of 40, in frequencies ranging from 0.8 × 10−4 to 10.2 × 10−4. Upon removal of Ac, each of the 40 mutations was stabilized as colorless or pale, indicating insertion of a Ds element at the R locus. When placed in heterozygous combination with r-sc:m3 (Ac absent), all but possibly 1 of the 38 mutants tested gave R-sc recombinants, showing that insertion had occurred in sites different from that in r-sc:m3. Thirty-eight of the 40 new mutable alleles that were examined by Southern blotting contained a Ds insert of 2.1 kbp, the same size as that found for r-sc:m3. These findings are consistent with the excision of Ds from r-sc:m3, followed by its insertion into a linked site in the R-sc revertant, and the subsequent reinsertion of the element into R. The testcrosses of R-sc revenants obtained from r-sc:m3 also produced five stable mutations to colorless or pale. In contrast with the r-sc:m3 revertant series, no r-mutable or stable variant was obtained from 10 R-sc revenants of r-sc:m1. Either the Ds involved (~ 400 bp) does not transpose to linked sites preferentially or, when it does, it becomes relatively immobile.Key words: mutagenesis, transposable elements, Dissociation (Ds), Activator (Ac), maize.
Long-range mapping in the research and diagnosis of genetic disease
Authors: Ommen G. J. B. van , Pearson P. L.
Published: April 2011

This paper reviews current genetic and molecular biological methods that may be used in the so-called "reverse genetics" approach. These methods are the mapping, isolation, and study of the chromosomal DNA containing a previously unidentified gene responsible for a genetic disease, beginning with its chromosomal localization. In principle, the reverse genetics methodology follows the same path for different diseases studied. An overall outline of the steps to be undertaken is given and discussed. Several stages are illustrated with reference to current research in the fields of Duchenne muscular dystrophy, Huntington's disease, and polycystic kidney disease.Key words: human genetic disease, Duchenne muscular dystrophy, Huntington disease, polycystic kidney disease, reverse genetics.
Computers: the best friends a human genome ever had
Authors: Kelly Michael J.
Published: April 2011

Mapping and sequencing the human genome will generate large amounts of data, which must be sorted, analyzed, and stored for rapid retrieval to complete this enormous task. Computers and their software programs provide the most important tool to the molecular biologist today. A discussion of current capabilities and future needs in computer hardware and software for the human genome project is the topic of this paper. The use of computer programs to generate restriction maps, manage clone libraries, manage sequence projects, and generate consensus sequences is presented. The use of computers to communicate useful information rapidly to scientific colleagues is also mentioned. The role of both GenBank and BIONET is central to the dissemination and analysis of sequence information. The capabilities of electronic communication worldwide for assisting this project is available on the BIONET National Computer Resource, using existing networks.Key words: human genome, computers, software, clones, GenBank, BIONET, restriction maps, nucleic acid sequences.
Future growth in biotechnology in the developing countries
Authors: Riazuddin S. , Nasim Anwar
Published: April 2011

Conditions in developing countries are nowhere near what they should be to reap the benefits of modern biotechnology. Be that as it may, there are possibilities in which intelligent thinking and rational planning by the people concerned, combined with input from international agencies and national centres of excellence, can lead to potential economic gains. One possibility is the establishment of collaborative research on a regional basis to tackle common problems and to train each other's manpower in acquired skills. Similarity of circumstances would make these programmes more relevant and cost effective. To ensure the success of joint programmes in the local setting, foreign input in the form of finances, provision of critical laboratory materials, and expert advice in the selection of technically solvable problems becomes inevitable. Thus participation by the developed-country agencies and laboratories in the developing countries presents a purposeful pooling of efforts that will sow the seeds for sustainable development of the developing world. Given that, new technology would prove a boon and a blessing for humanity in general and for the developing world in particular.Key words: biotechnology, developing countries.
Allotetraploid behavior of hybrids of Medicago sativa L. and M. papillosa Boiss.
Authors: McCoy T. J. , Quarisa G. L.
Published: April 2011

Diploid (2n = 2x = 16), triploid (2n = 3x = 24), and tetraploid (2n = 4x = 32) interspecific hybrids between alfalfa (Medicago sativa L.) and M. papillosa Boiss. were recovered either from seed (the triploid hybrids) or from ovule–embryo culture (the diploid and tetraploid hybrids). Cytogenetic analysis of diploid interspecific hybrids (with one genome of M. sativa, designated S, and one genome of M. papillosa, designated P), indicated significant genomic affinity, with an average of 7.6 bivalents and 0.8 univalents per pollen mother cell. In contrast, cytogenetic analysis of the triploid interspecific hybrids (with one S genome and two P genomes) indicated little if any genomic affinity between M. sativa and M. papillosa. In 7 of 14 triploid hybrids analyzed no trivalent configurations were observed, and in the other hybrids, trivalent frequency ranged from 0.1 to 0.4 per pollen mother cell. Tetraploid interspecific hybrids with two S and two P genomes had predominantly bivalent pairing. Based on the lack of homology of S and P genomes, the tetraploid hybrids are basically allotetraploids (SSPP). Therefore, backcross progeny from crossing the tetraploid hybrids with tetraploid M. sativa have the genomic constitution SSSP. Univalents and trivalents were observed in first backcross (BC1) progeny, as expected, based on an allotetraploid interpretation. Most of the BC1 progeny were partially or completely male sterile, and female fertility was significantly reduced. Potential uses of homoeologous genomes such as M. papillosa in alfalfa genetic and breeding studies are discussed.Key words: cytogenetics, interspecific hybrids, ovule –embryo culture.
Transmission of an alien telocentric addition chromosome in common wheat that confers blue seed color
Authors: Whelan E. D. P.
Published: April 2011

Phenotypic markers of chromosomes are useful for determining chromosome behavior in cytogenetic studies. Transmission of an alien, telocentric addition from Agropyron tricophorum (Link) Richt. that confers purple aleurone pigment and blue seed color was evaluated in common wheat (Triticum aestivum L.). Twenty-five of 2570 seeds from bagged heads of eight ditelocentric-addition sister plants were almost white rather than blue. Seven of these 25 seeds and 4 of 336 blue seeds segregated 41.4%:58.6% blue:white. Meiotic analyses showed that all plants grown from these 11 seeds were spontaneously produced monotelocentric additions. Transmission of the alien telocentric chromosome through the egg and the pollen was estimated to be 19.5 and 14.3%, respectively, based on BC1F1 seed color. About 28% of F2 and F3 seeds were blue; of these 7.4% were ditelocentric additions. The frequency of blue seed in F2 progeny from spontaneous monotelocentric additions (41.4%) was significantly greater than that of monotelocentric additions from controlled crosses (28%). Penetrance of the blue seed color gene(s) associated with the alien telocentric chromosome was good. Misclassification of seed color for 1595 BC1F1 seeds was less than 3% based on BC1F2 progeny.Key words: Agropyron tricophorum.
Multilocus genetic structure, characterization, and relationships of Populus × canadensis cultivars
Authors: Rajora Om P. , Zsuffa Louis
Published: April 2011

The genotypes of 21 clones of 18 Populus × canadensis Moench cultivars ('Baden 431', 'Blanc du Poitou', 'Canada Blanc', 'DN44', 'Dorskamp 925', 'Eugenei', 'Gelrica', 'Grandis', 'Heidemij', 'I-55/56', 'I-132/56', 'I-262', 'Jacometti', 'Ostia', 'Regenerata', 'Robusta', 'Steckby', and 'Zurich 03/3') were determined for 31 allozyme loci coding for 9 enzyme systems in root tips. Horizontal starch gel electrophoresis was used to assay the enzymes. All clones had allozyme gene and allele contribution from both P. deltoides Marsh, and P. nigra L. The interclonal allozyme variability was controlled by nine loci. 'Canada Blanc' and 'Ostia' shared the same 31-locus genotypes, whereas each of the remaining 19 clones, including 3 clones of 'Robusta' and 2 clones of 'Jacometti', had unique multilocus genotypes. On average, unique genotypes differed from each other at 3.59 loci. Principal-component analysis of the clonal genotypes at 9 variable loci indicated 4 loci (Idh-2, Idh-3, Mdh-4, and Idh-1) to be the most discriminating among the clones. The first two principal components accounted for 48% of the total variance in the nine loci. Clones on the principal component analysis ordination (principal components 1 and 2) were separated into 3 groups; 14 belonged to one group and 5 to a second group. 'Blanc du Poitou' was widely separated from all others. 'Canada Blanc' and 'Steckby' showed the highest genetic interrelationships. Three 'Robusta' clones and two 'Jacometti' clones were in the same group., The interrelationships among the clones based on allozyme genotypes were in general agreement with their speculated origin and (or) morphology.Key words: Populus × canadensis, allozymes, multilocus genotypes, clone–cultivar identification, clone relationships.
Organisation de la variabilité enzymatique des populations marocaines de luzerne (Medicago sativa L.): structures géniques et génotypiques
Authors: Birouk A. , Dattée Y.
Published: April 2011

Five enzymatic loci have been analyzed electrophoretically to study the genic and genotypic structures of 20 populations of alfalfa (Medicago sativa L.) from Morocco. Five different geographical origins were considered: Ziz, Drâa and Dadès (three oases in the Sahara), Demnate, and oases from mountainous regions. For comparison, three cultivars (African, Moapa, Europe) and four populations (one from Sudan, two from Spain, and one from Provence) of foreign origin were included in the study. The genic structures of the above 27 populations or cultivars allowed a good discrimination among populations and origins. The alleles with low frequency played a significant role in the discrimination and the discrimination was better when established on the basis of allelic diversity than on genotypic structures. The Flemish cultivar Europe differed from all other mediterranean material (African, Moapa, Provence, Morocco populations) but closely resembled two Spanish ecotypes from Mielga. The cultivars African and Moapa proved to be different from the Morocco populations. The latter could be divided into two different genic pools: one consisted of the Demnate populations, the other grouped populations of the Sahara and mountainous oases with no clear distinction between geographical origins. Genotypic structures based on the analyses of 30 plants from each population or cultivar did not allow to discriminate among populations. To study fixation indices and verify the panmictic equilibrium hypothesis, the number of specimen per population or cultivar had to be increased for a few populations. All the populations or cultivars analyzed showed a lack of heterozygous plants and the hypothesis of a Hardy–Weinberg equilibrium could not be accepted. Frequencies of monogenic individuals and digenic duplexes were high, but tetragenic individuals were infrequent.Key words: alfalfa, isozymes, genic structures, genotypic structures, infrequent alleles.[Journal translation]
Relatedness of three species of Agaricus inferred from restriction fragment length polymorphism analysis of the ribosomal DNA repeat and mitochondrial DNA
Authors: Hintz William E. A. , Anderson James B. , Horgen Paul A.
Published: April 2011

The ribosomal DNA (rDNA) repeat of Agaricus brunnescens (= A. bisporus) was cloned and mapped for six restriction endonucleases. The map positions of the 26S, 18S, and 5.8S rRNA genes on the 9.2 kilo base pairs (kbp) repeat were determined by alignment of sites conserved in the rRNA genes of other fungi. The rDNA restriction site maps for six isolates of A. brunnescens, five isolates of A. bitorquis, and three isolates of A. campestris were compared using cloned A. brunnescens (Ag 50) rDNA as a hybridization probe. The rDNA restriction patterns for all six A. brunnescens isolates were identical. The A. bitorquis and A. campestris isolates were subdivided into two groups each, according to rDNA restriction-site polymorphisms. The A. brunnescens and A. bitorquis rDNAs were distinguished by a 0.7 kbp length difference in the noncoding spacer between the 18S and 26S rRNA genes. Despite the almost perfect conservation of the coding region between species, the noncoding spacers of A. campestris and the other two Agaricus species were too divergent to propose a simple series of mutational events to account for the differences. Interstrain and interspecies variation in the mitochondrial DNA was also surveyed. Strain-specific mitochondrial DNA restriction patterns were recognized and fewer differences were observed between the A. brunnescens and A. bitorquis isolates than between A. campestris and the other two species.Key words: Agaricus brunnescens (= A. bisporus), Agaricus, rDNA, mitochondrial DNA, restriction fragment length polymorphism analysis.
Chromosome pairing in the Triticum monococcum complex: evidence for pairing control genes
Authors: Shang X. M. , Jackson R. C. , Nguyen H. T. , Huang J. Y.
Published: April 2011

The occurrence and behavior of pairing control genes at the diploid level were analyzed by using the models and equations developed by Jackson and co-workers. It appears that all pairing control genes are codominant and they are detectable only as heterozygotes in diploids. The phenotypic expressions of such genes are the production of univalents, and this is positively correlated with the occurrence of unpaired chromosome segments at pachytene. Analyses of a large number of accessions of the Triticum monococcum complex and various hybrid combinations have also shown that pairing control gene alleles occur within accessions of the same diploid species and in intraspecific and interspecific hybrids. Strength differences among the pairing control alleles are indicated by different frequencies of univalents at the diploid level, and the occurrence of pairing control genes is not correlated with taxonomic units.Key words: mathematical models, meiotic analyses, pairing control gene, heterozygotes, pachytene, Triticum diploids.
Chromosome structural changes and their role in the evolution of tetraploid wheats
Authors: Noda Kaz. , Koulin Ge
Published: April 2011

The possibility that chromosomal interchanges present in the Timopheevi group (AAGG) are responsible for the differentiation of two different groups of tetraploid wheats, the Emmer group (AABB) and the Timopheevi (AAGG) group, has been examined. Chromosomes of Triticum dicoccoides (2n = 28, AABB) and six interchange types of the Timopheevi group (2n = 28, AAGG) were studied by N-banding. The banding patterns of the G genome were distinct from those of the B genome. The banding patterns of the G genome chromosomes of the interchange types were similar to the basic banding patterns of the G genome except those of interchanged chromosomes. No intermediate banding patterns between the B and G genomes were observed. These interchanges might have occurred after establishment of the basic karyotype of the G genome and would not be related to the differentiation of AABB and AAGG from a progenitor tetraploid, such as amphidiploid (AASS) between Aegilops speltoides (SS) and Triticum boeoticum (AA).Key words: tetraploid wheats, N-banding, interchange.
Chromosome segregation from cell hybrids. VI. Centromeres of both parental chromosome sets stain with antikinetochore antibody
Authors: Zelesco Paula A. , Graves Jennifer A. Marshall
Published: April 2011

Antikinetochore antibodies obtained from serum of patients with the CREST syndrome of scleroderma were used to test the hypothesis that there are differences in protein binding to retained- and segregant-set centromeres in Chinese hamster – human hybrids. This hypothesis is not supported since identical staining of the two types of kinetochores was observed with CREST antibody.Key words: chromosome segregation, antikinetochore staining, CREST antibodies, cell hybrids.
Extraction of disomic addition lines of Brassica napus – B. nigra
Authors: Jahier J. , Chèvre A. M. , Tanguy A. M. , Eber F.
Published: April 2011

The hybrid Brassica napus × B. nigra was produced and backcrossed three times to rapeseed. BC3 genotypes with one or two additional chromosomes were either selfed or haplodiploidized by using anther culture followed by colchicine doubling. Thirty-four fertile disomic addition lines have so far been obtained. Meiotic pairing in most of them was close to 20 II at metaphase I of meiosis. Their characterization is in progress. This material obtained for the first time in B. napus should be of great interest in the study of genome structure and basic chromosome number in Brassica species.Key words: Brassica, genome, disomic addition lines, meiotic behaviour.
Concepts of varietal value and of test value in autotetraploids. Application to genetic advance in population improvement
Authors: Gallais A.
Published: April 2011

The application to autotetraploids of the concepts of varietal value and of test value allows the derivation of expressions of genetic advance for the different types of varietal values (per se value, line value, single-cross or double-cross values, synthesizing ability) according to the testing system used to select the intercrossed plants. Formulae are given for series of intrapopulation schemes and for reciprocal recurrent selection. With autotetraploids, if non-inbred plants are intercrossed and when epistasis is not involved, there is a contribution of additive effects and of dominance effects for the considered testing systems. However, it is shown that, except for mass selection or S1 selection devoted to improve the per se value of the population, the contribution of dominance is very low. The formulae are exactly the same as for diploids if the contribution of dominance variance is neglected.Key words: autopolyploid, quantitative genetics, varietal ability, test value, recurrent selection.
Monosomic alien addition lines of rice: production, morphology, cytology, and breeding behavior
Authors: Jena K. K. , Khush Gurdev S.
Published: April 2011

Interspecific hybrids between three breeding lines of Oryza sativa (2n = 24 = AA) and 18 accessions of O. officinalis (2n = 24 = CC) were obtained through an embryo-rescue technique. The crossability ranged from 1.0 to 2.3%. The AC hybrids showed a low amount of chromosome pairing (0–4 bivalents) and were completely male sterile. The BC1 progeny, obtained upon backcrossing to O. sativa were allotriploid (AAC) and were also male sterile. Further backcrosses to O. sativa produced 94 BC2 plants with chromosome numbers of 2n to 2n + 6. Monosomic alien addition lines (AA + 1C) corresponding to the 12 chromosomes of the haploid complement of O. officinalis were isolated from among forty 2n + 1 BC2 plants. These addition lines differ from their diploid sibs by an array of morphological features and resemble the 12 primary trisomics of O. sativa. The female transmission rates of alien chromosomes varied from 6.6 to 26.8%. Four of the 12 monosomic alien addition lines transmitted the alien chromosome through the male gametes.Key words: chromosome pairing, introgression, embryo rescue, allotriploid, genes for insect resistance, interspecific gene transfer.
Genetic basis of sterility in hybrids from crosses of Glossina morsitans submorsitans and Glossina morsitans morsitans (Diptera: Glossinidae)
Authors: Gooding R. H.
Published: April 2011

Glossina morsitans submorsitans Newstead and Glossina morsitans morsitans Westwood carrying two marker genes on the X chromosome, two in linkage group II, and one in linkage group III were hybridized. About 17% of the F1 and from 33 to 56% of the backcross males fertilized G. m. submorsitans, but only one F1 and two backcross males fertilized G. m. morsitans. Similarly, F1 and backcross females were fertilized by G. m. submorsitans but rarely by G. m. morsitans. Chromosomal composition of F1 and backcross males indicated that hybrid male sterility is due to incompatibility of the X chromosome from one subspecies and the Y from the other subspecies or possibly an incompatibility between X chromosomes and autosomes from different subspecies. Results are discussed in the context of a model for evolution of X and Y incompatibility and a model for evolution of maternally inherited factors that cause unidirectional sterility in males. In hybrid females, intrachromosomal recombination was suppressed in the X chromosome and in linkage group II. Fertility of backcross females, mated to G. m. submorsitans, could not be related to the chromosomal composition of the females.Key words: Glossina, hybrid sterility, tsetse, X chromosomes.
Chiasmata and recombination nodules in Lilium longiflorum
Authors: Stack Stephen M. , Anderson Lorinda K. , Sherman Jamie D.
Published: April 2011

We determined the frequency of chiasmata at late diplotene in microsporocytes of Lilium longiflorum (lily). Because there are long, intimate associations of homologous chromosomes in addition to short associations that appear to be single chiasmata, the number of chiasmata counted depends on how the long associations are interpreted. Using a defined method, we determined that there was an average of 54.8 ± 6.0 chiasmata per complete set of diplotene bivalents. Recombination nodules are 100-nm ellipsoids that are found on the central element of synaptonemal complexes. There is correlative evidence that strongly indicates recombination nodules are located at the sites of crossing-over in late pachytene. Using spreads of synaptonemal complexes stained with uranyl acetate – lead citrate, we determined that the frequency of recombination nodules was 1/57.2 μm of synaptonemal complex. Using separate silver-stained spreads of synaptonemal complexes from lily microsporocytes, we determined that the average length of a complete set of pachytene synaptonemal complexes was 3149 ± 668 μm. Therefore, an average set of synaptonemal complexes would have 55.1 (3149 ÷ 57.2) recombination nodules, a number that closely matches the average number of chiasmata in a set of late diplotene bivalents.Key words: chiasmata, recombination nodules, synaptonemal complex, Lilium longiflorum.
FOREWORD/PRÉFACE
Authors: Moens Peter B.
Published: April 2011

One of Canada's outstanding cytogeneticists, Klaus Rothfels, died unexpectedly in 1987. A group of his former students and colleagues have arranged a series of research articles that reflect the nature of Dr. Rothfels' scientific work and his inspiration to others.A world leader in the evolutionary analysis of speciation in black flies, his legacy in that field is most strongly represented in this series. Included is a posthumous synthesis of Klaus' work entitled Speciation in black flies. This paper was assembled by his graduate students and it is presented as such, unrefereed.Klaus' single most celebrated discovery, the air drying of chromosome spreads for karyotyping, has been highlighted in Citation Classics of Current Contents (27(3): 19. 1984). His reminiscence of the discovery was also published in the Bulletin of the Genetics Society of Canada (16(1): 15. 1985).I thank the reviewers who contributed their time and talents to this memorial publication. All of us miss Klaus Rothfels as a scientist and as a person.
An experimental comparison of selection methods
Authors: Winkelman D. C. , McMillan I. , Friars G. W. , McKay L. R.
Published: April 2011

Five methods of selection each in five replicates were examined for single-generation response in high and low 21-day pupal weight of Tribolium castaneum. The methods of selection tested were individual (ID), dam family or full (DF), sire family or half-sib (SF), progeny test (PT), and index (IX). A selection intensity, involving as parents the top 25% of the individuals on any specific phenotypic scale, was applied throughout the experiment. Each replicate included a contemporaneous, randomly mated control line. Responses attained with each method were compared with predicted gains and with results observed for other methods. Differences in responses of males and females were also assessed. Response to selection was markedly asymmetrical with greater gains observed in the downward direction. In the lines selected for low pupal weight, males and females were found to respond similarly and actual responses did not differ from those predicted. Ranking of methods by responses obtained for downward selection yielded the order IX > ID > PT > DF > SF. Selection for high pupal weight yielded differences in responses of males and females and the observed responses were significantly less than those predicted in all cases except that of PT-selected females. Observed responses for males were ordered as IX > ID > PT > DF > SF, while those for females were PT > IX > DF > SF > ID. When the data from both sexes were combined, the order of responses was PT > IX > DF > ID > SF.Key words: asymmetrical response, selection, Tribolium, pupal weight.
Influence of the Oryza sativa genotype on the fertility and quantitative traits of F1 hybrids between the two cultivated rice species O. sativa L. and O. glaberrima Steud.
Authors: Bougerol Bruno , Pham Jean-Louis
Published: April 2011

Crosses were carried out between the two cultivated rice species, using a constant Oryza glaberrima parent and 14 O. sativa cultivars, including 11 traditional African ones. The F1 hybrids were studied for quantitative traits and their fertility. Analyses of the quantitative traits revealed the intermediate position of F1 s with respect to the parental lines and the high heritability of several characters, including the secondary branching within the panicle. All F1 hybrids showed complete seed sterility and only by an examination of the pollen could the different combinations be discriminated. The hybrids obtained from two O. sativa cultivars introgressed from the wild species O. longistaminata were particularly sterile.Key words: rice, Oryza sativa, Oryza glaberrima, interspecific hybridization, sterility, quantitative inheritance.
Linkage and segregation distortion in Drosophila melanogaster
Authors: Sharp Cecil B. , Hilliker Arthur J.
Published: April 2011

Segregation distortion is caused by a group of genetic elements in and near the centric heterochromatin of chromosome 2 of Drosophila melanogaster. These elements promote their preferential recovery in heterozygous males by rendering sperm bearing the homologous chromosome dysfunctional. Previous work has shown that numerous Y–autosome translocations are associated with the suppression of the segregation distorter phenotype. The present study examined the effects of translocations between the major autosomes upon the expression of segregation distortion. Autosomal translocations involving either the segregation distorter chromosome or its sensitive homologue had no significant effect upon the expression of segregation distortion. These results argue that linkage arrangement per se may not have a major effect on segregation distortion. The suppression of SD by specific Y–autosomal translocations may be due to the disruption of elements on the Y chromosome that are important for the expression of SD.Key words: segregation distortion, meiotic drive, translocations, Drosophila melanogaster.
BKm minisatellite sequences are not sex associated but reveal DNA fingerprint polymorphisms in rainbow trout
Authors: Lloyd Marilyn A. , Fields Mary J. , Thorgaard Gary H.
Published: April 2011

GATA-GACA repetitive sequences first isolated from a female snake (termed BKm sequences) and associated with sex chromosomes in some species were hybridized to DNA from rainbow trout (Salmo gairdneri). Genomic DNA was studied from three groups of rainbow trout: (i) randomly selected males and females from an outbred group, (ii) androgenetic individuals from an inbred strain, and (iii) parents and offspring of an outbred strain. Three restriction enzymes (EcoRI, HaeIII, or HinfI) were used to digest the genomic DNA. The DNA was electrophoresed in agarose gels, transferred to nylon membranes, and the GATA-GACA repetitive sequence probe was hybridized to this DNA. There was no evidence of sex-associated patterns of hybridization with the enzymes used. However, the sequences reveal DNA fingerprint polymorphisms which appear to be inherited in a stable manner.Key words: BKm, GATA-GACA repetitive sequences, DNA fingerprint, rainbow trout, Salmo gairdneri.
Genome relationship between Thinopyrum bessarabicum and Thinopyrum elongatum
Authors: Forster B. P. , Miller T. E.
Published: April 2011

Two wheat/Thinopyrum amphiploids, wheat/T. bessarabicum and wheat/T. elongatum were crossed together and meiosis was studied in the F1 hybrid. The data show that although the wheat chromosomes pair fully, those of the two diploid Thinopyrum species rarely pair, 21 bivalents plus 14 univalents being the modal configuration. The genome symbols E for T. elongatum and Eb for T. bessarabicum are proposed.Key words: Thinopyrum elongatum, Thinopyrum bessarabicum, genome relationship.
Multivalent formation and pairing behavior of germ line limited chromosomes in male meiosis of Acricotopus lucidus (Diptera, Chironomidae)
Authors: Staiber Wolfgang
Published: April 2011

The pairing behavior of the germ line limited chromosomes of Acricotopus lucidus was investigated in male meiosis using G-banding. Each of the nine different types of limited chromosomes can be absent or can be present in metaphase I with two or four homologous chromosomes, one type even with up to 10. Usually the homologues form bivalents, but frequently quadrivalents and also hexavalents consisting of the same chromosome type were observed. In some cases multivalents composed of different limited chromosomes occurred. This resulted probably from pairing and crossing-over between hom(oe)ologous segments in otherwise nonhomologous chromosomes. The observations are discussed in relation to origin and diversity of the germ line limited chromosomes.Key words: germ line limited chromosomes, multivalent formation, male meiosis, Acricotopus lucidus.
Sélections sur la phase haploïde chez le Mil (Pennisetum typhoides (Burm.) Stapf et Hubb.): effet de la température
Authors: Robert T. , Sarr A. , Pernès J.
Published: April 2011

Intergametophytic competitions with a polygenic inheritance trend have been previously described in pearl millet. This study puts emphasis on the effect of environmental parameters, particularly temperature, on the segregation of five genes encoding for enzyme proteins. F2 progenies of selfed F1 plants grown under three temperature regimes (22 °C constant, 27/17 °C, and 32/27 °C (day/night)) were studied. Significant segregation distortions were found for four genes. It is shown that the selection pressures placed on the free haploid phase by pollen competition are enhanced by temperature. Furthermore, genotype × environment interactions influence the gametophytic competitive ability of the parental genotypes. The hypothesis of genetic linkage between these marker loci and the chromosomal sectors responsible for pollen competitive ability is discussed. We also discuss the role these selective mechanisms and their consequences on the genetic makeup of the following generations may play in plant breeding, population genetics, and genetic resources management.Key words: pearl millet, segregation distortions, gametophytic selections.
Para-Fluorophenylalanine-induced chromosome number changes in higher plants. I. Maize
Authors: Banks P. , Britten E. J. , Gordon G. H.
Published: April 2011

Excised maize embryos and germinating maize seeds were treated with para-fluorophenylalanine to induce chromosome changes. Aneuploidy and changes in ploidy levels were observed. Identified hypoploid changes involved the loss of a single chromosome and, in one case, the loss of one arm of a chromosome. Hyperploids included trisomics, double trisomics, and probably tetrasomics. The use of karyotype analysis demonstrated that at least 6 of the 10 maize chrosssmosomes were involved in these modifications. Analysis of chromosome numbers in progeny indicated the "likely" chromosome number of the reproductive tissue of treated plants. In some treated plants the likely chromosome number of the reproductive tissue was the same as that observed in adventitious roots, while in others it was different from that of their adventitious roots. The use of para-fluorophenylalanine may be of value in plants other than maize for purposes of chromosome number engineering.Key words: aneuploids, chromosome number changes, maize, para-fluorophenylalanine, Zea mays.
Linkage analysis and arm location of the open bud (ob1) and yellow petal (Y2) loci in chromosome 18 of cotton
Authors: Endrizzi J. E. , Nelson R.
Published: April 2011

An open bud mutant phenotype was recovered in the transference of the yellow petal (Y2) gene from Gossypium darwinii to G. hirsutum. The open bud mutant is allelic to the open bud (ob1) mutant in G. hirsutum. By the induction and use of monotelodisomes it was shown that the open bud and yellow petal genes are located, respectively, on the short and long arms of chromosome 18. The ob1 gene is 3.4 and the Y2 gene is 8 map units from the centromere; thus the two loci are at least 11 map units apart.Key words: monosome, telosome, linkage, Gossypium mutants.
Cytogenetics of the Herbert River ringtail possum, Pseudocheirus herbertensis (Diprotodonta: Pseudocheiridae): evidence for two species
Authors: Murray J. D. , McKay G. M. , Winter J. W. , Ingleby S.
Published: April 2011

The two Herbert River ringtail possum subspecies, Pseudocheirus herbertensis ssp. herbertensis and P. h. ssp. cinereus, have diploid chromosome numbers of 12 and 16, respectively. The sex chromosomes of both subspecies are exceptionally large, with the X and Y chromosomes being approximately 16 and 12% of the haploid autosomal complement, respectively. A sex chromosome bivalent cannot be identified during male meiosis and a sex vesicle is not present during pachytene. The two karyotypes are most likely related by two centric fusion events affecting the autosomal complement. We conclude that the X and Y chromosomes have been translocated onto homologous autosomes to give t(XA) t(YA) ♀ t(XA) t(XA) ♂. Our data also strongly support the separation of P. h. cinereus as a distinct species.Key words: karyotypes, sex chromosomes, speciation.
Allozyme divergence and evolutionary relationships among Populus deltoides, P. nigra, and P. maximowiczii
Authors: Rajora Om P. , Zsuffa Louis
Published: April 2011

Horizontal starch gel electrophoresis of enzymes was used to study genetic divergence among Populus deltoides Marsh. (section Aigeiros Duby, Salicaceae), P. nigra L. (section Aigeiros), and P. maximowiczii Henry (section Tacamahaca Spach.) at 37 to 40 allozyme loci coding for 12 enzyme systems in root tips. These three Populus species were genetically distinct from each other. Populus deltoides, P. nigra, and P. maximowiczii had mutually exclusive alleles at two loci, and each of these species had unique alleles at many loci. Certain allozyme loci were detected only in one or two of these species. Frequency distributions of allozyme loci were bimodal with respect to genetic identity for comparisons between any two species. The mean genetic distance was 0.36 ± 0.10 between P. deltoides and P. nigra, 0.39 ± 0.09 between P. deltoides and P. maximowiczii, and 0.34 ± 0.10 between P. nigra and P. maximowiczii. The enzyme electrophoretic evidence indicated a monophyletic origin of the three Populus species.Key words: poplars, genetic identity and divergence, allozymes, molecular evolution, phylogenetics.
A cytogenetic survey of 25 species of lower termites from Australia
Authors: Luykx Peter
Published: April 2011

A survey of 25 species of lower termites (families Mastotermitidae, Termopsidae, and Kalotermitidae) in Australia revealed that centric fusions are a common theme in karyotype evolution in these insects. All but one of the species studied have a basic XX/XY mechanism of sex determination, secondarily complicated in about a third of a species by centric fusions between autosomes and sex chromosomes. There is no obvious relationship between systematic position and presence or absence of these fusions. Fusions between Y chromosomes and autosomes were more common than fusions between X chromosomes and autosomes, in accord with the prediction of the hypothesis that differential selection between the two sexes is the basis for the spread of sex-linked fusions. The absence of these fusions in many species does not favor the idea that a high degree of sex linkage is a necessary condition for the establishment or maintenance of eusocial behavior in termites. The difference in the mechanism of sex determination from that of cockroaches (XX/XO) argues against the evolutionary derivation of termites from ancestral cockroaches; derivation of both groups from some common ancestor with XX/XY sex determination is more likely.Key words: termites, karotype, evolution, sex chromosomes, Australia.
Analysis of lethal mutations induced in a mutator strain that activates transposable elements in Caenorhabditis elegans
Authors: Clark Denise V. , Johnsen Robert C. , McKim Kim S. , Baillie David L.
Published: April 2011

A screen was conducted for lethal mutations in the nematode Caenorhabditis elegans in a strain containing the mutator mut-4(st700)I to examine the nature of mutator-induced lethal mutations within two large chromosomal regions comprising a total of 49 map units (linkage group IV (right) and linkage group V (left)). The genetic analysis of 28 lethal mutations has revealed that the mutator locus mut-4(st700)I causes both putative single-gene mutations and deficiencies. We have identified lethal mutations in three different genes, in addition to seven deficiencies. There is a mutational hot spot on linkage group V (left) around the lin-40 locus. Six mutations appear to be alleles of lin-40. In addition, 5 of 7 deficiencies have breakpoints at or very near lin-40. All seven deficiencies delete the left-most known gene on linkage group V (left) and thus appear to delete the tip of the chromosome. This is in contrast to gamma ray and formaldehyde induced deficiencies, which infrequently delete the closest known gene to the tip of a chromosome.Key words: Caenorhabditis elegans, mutator, deficiencies, lethal mutations.
Study of chromosomes, DNA amount, and in vitro growth in different species of Luzula
Authors: Sen Jayanti , Mukherjee Sumona , Sharma A. K.
Published: April 2011

Cells of six different species of Luzula were subjected to in vitro culture and examined for callus formation. The cells of calli from the different species were analyzed for variation in chromosome number. The cells of different species showed a differential response in culture with respect to callus growth. Chromosome number variation in vitro, including both hypo- and hyper-diploidy, was recorded in all species except L. pediformis and L. luzuloides. The chromosome fragments survived as a result of a nonlocalized centromere. With prolonged culture, normal diploid cells were frequent. The nuclear DNA content of cells of these species was also measured, both in vivo and in vitro. The DNA values ranged from 6.05 to 7.03 pg per 4C nucleus. No marked change in DNA value was noted in cells even with high chromosome numbers, thereby confirming their origin through fragmentation of chromosomes. In cells of callus, the DNA amount was observed to be higher than in normal cells, indicating fragmentation and duplication of individual chromosomes. Their importance in the origin of new genotypes has been indicated.Key words: Luzula spp., in vitro growth, chromosomes, nuclear DNA content.