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Results for “Hybridization, Genetic”

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PubMed1997

[Genomic incompatibility in Drosophila virilis Sturt. X Drosophila lummei Hackman hybrids].

Genetic analysis of male sterility in Drosophila virilis x D. lummei hybrids was performed. It was shown that hybrid male sterility was caused mainly by incompatibility of sex chromosomes X and Y and homozygous chromosome 2 of D. virilis with other autosomes of D. lummei. Genes of chromosomes 3 and 5 enhanced sterility whereas genes of chromosome 4 suppressed its development. Factors controlling hybrid male sterility were demonstrated to have a recessive type of inheritance. At 17 degrees C, chromosome 6 of D. lummei was eliminated in F1 hybrids of the cross female D. virilis x male D. lummei. At 17 degrees C and 25 degrees C, sterility of the F1 hybrid males was 96% and 9%, respectively. Thus, two isolation mechanisms-elimination of chromosome 6 and male sterility-can simultaneously operate in F1. In addition to the region of the species-specific inversion In 1(a+b), factors controlling male sterility were mapped to the vermillion region of the X chromosome.

Animals↗

PubMed2006

Genetic alterations in primary gastric carcinomas correlated with clinicopathological variables by array comparative genomic hybridization.

Genetic alterations have been recognized as an important event in the carcinogenesis of gastric cancer (GC). We conducted high resolution bacterial artificial chromosome array-comparative genomic hybridization, to elucidate in more detail the genomic alterations, and to establish a pattern of DNA copy number changes with distinct clinical variables in GC. Our results showed some correlations between novel amplified or deleted regions and clinical status. Copy-number gains were frequently detected at 1p, 5p, 7q, 8q, 11p, 16p, 20p and 20q, and losses at 1p, 2q, 4q, 5q, 7q, 9p, 14q, and 18q. Losses at 4q23, 9p23, 14q31.1, or 18q21.1 as well as a gain at 20q12 were correlated with tumor-node-metastasis tumor stage. Losses at 9p23 or 14q31.1 were associated with lymph node status. Metastasis was determined to be related to losses at 4q23 or 4q28.2, as well as losses at 4q15.2, 4q21.21, 4q 28.2, or 14q31.1, with differentiation. One of the notable aspects of this study was that the losses at 4q or 14q could be employed in the evaluation of the metastatic status of GC. Our results should provide a potential resource for the molecular cytogenetic events in GC, and should also provide clues in the hunt for genes associated with GC.

Adult↗

PubMed1971

Cotransduction of strA and ribosomal protein cistrons in Escherichia coli-Salmonella typhimurium hybrids.

Genetic mapping of ribosomal protein cistrons of Salmonella typhimurium and Escherichia coli was performed by phage P1 mediated, generalized transduction. From an E. coli hybrid strain which carried a S. typhimuirum F' factor, an E. coli strain was constructed which had integrated S. typhimurium genetic material including the region of the strA locus. Salmonella genetic material from this hybrid was transduced into E. coli recipients. The ribosomal protein electrophoretic patterns of these hybrid transductants were correlated with the presence of markers contributed by each parent. The results of these studies indicate that cistrons for at least three characteristic S. typhimurium and two E. coli 30S ribosomal proteins are closely linked to the strA locus on the genetic maps of both organisms. At least one cistron coding for a 50S ribosomal protein is also closely linked to this locus on both maps. These findings support the concept that cistrons coding for the ribosomal proteins are clustered in one area of the genome. Mutations to spectinomycin and streptomycin resistance are closely linked in S. typhimurium and are located at strA.

Acrylates↗

PubMed2004

Genetics of hybrid inviability and sterility in Drosophila: dissection of introgression of D. simulans genes in D. melanogaster genome.

Interspecific crosses between Drosophila melanogaster and Drosophila simulans usually produce sterile unisexual hybrids. The barrier preventing genetic analysis of hybrid inviability and sterility has been taken away by the discovery of a D. simulans strain which produces fertile female hybrids. D. simulans genes in the cytological locations of 21A1 to 22C1-23B1 and 30F3-31C5 to 36A2-7 have been introgressed into the D. melanogaster genetic background by consecutive backcrosses. Flies heterozygous for the introgression are fertile, while homozygotes are sterile both in females and males. The genes responsible for the sterility have been mapped in the introgression. The male sterility is caused by the synergistic effect of multiple genes, while the female sterility genes have been localized to a 170 kb region (32D2 to 32E4) containing 20 open reading frames. Thus, the female sterility might be attributed to a single gene with a large effect. We have also found that the Lethal hybrid rescue mutation which prevents the inviability of male hybrids from the cross of D. melanogaster females and D. simulans males cannot rescue those carrying the introgression, suggesting that D. simulans genes maybe non-functional in this hybrid genotype. The genes responsible for the inviability have not been separated from the female sterility genes by recombination.

Animals↗

PubMed1993

Sexual isolation between Drosophila melanogaster females and D. simulans males. Male mating propensities versus success in hybridization.

Genetic variation has been found in males of a D. simulans population for their eagerness to hybridize with D. melanogaster females. In a search for traits involved in this hybridization, males of D. simulans were tested for mating speed and sexual vigour. Between-male differences were detected in both sexual traits, but no relationship was noticed between them, nor with the frequency of hybridization. Thus male mating propensities appear to be unrelated to the breakdown of sexual isolation between these sibling species.

Animals↗

PubMed1990

Identification of Haemophilus aphrophilus and Actinobacillus actinomycetemcomitans by DNA-DNA hybridization and genetic transformation.

DNA-DNA hybridization was used to identify clinical isolates as Haemophilus aphrophilus or Actinobacillus actinomycetemcomitans. Some of the isolates were naturally competent for genetic transformation and were also used as DNA recipients for identification of other isolates. The results obtained by hybridization were supported by interstrain-to-intrastrain transformation ratios. Distinction between the closely related species H. aphrophilus and A. actinomycetemcomitans was generally clear-cut by both methods. Distinction of H. aphrophilus and A. actinomycetemcomitans from type and reference strains of a diversity of species in the family Neisseriaceae and other gram-negative species was also demonstrated by both methods. This is the first description of the identification of clinical isolates of H. aphrophilus or A. actinomycetemcomitans by using them as recipients in genetic transformation. The results suggest that this is a reliable system for identification of new clinical isolates belonging to these taxonomic entities.

Actinobacillus↗

PubMed2003

Cleaner production for continuous digester processes based on hybrid Pareto genetic algorithm.

Pulping production process produces a large amount of wastewater and pollutant emitted, which has become one of the main pollution sources in pulp and paper industry. To solve this problem, it is necessary to implement cleaner production by using modeling and optimization technology. This paper studies the modeling and multi-objective genetic algorithms for continuous digester process. First, model is established, in which environmental pollution and saving energy factors are considered. Then hybrid genetic algorithm based on Pareto stratum-nichecount is designed for finding near-Pareto or Pareto optimal solutions in the problem and a new genetic evaluation and selection mechanism is proposed. Finally using the real data from a pulp mill shows the results of computer simulation. Through comparing with the practical curve of digester, this method can reduce the pollutant effectively and increase the profit while keeping the pulp quality unchanged.

Algorithms↗

PubMed2004

Genetics of hybrid incompatibility between Lycopersicon esculentum and L. hirsutum.

We examined the genetics of hybrid incompatibility between two closely related diploid hermaphroditic plant species. Using a set of near-isogenic lines (NILs) representing 85% of the genome of the wild species Lycopersicon hirsutum (Solanum habrochaites) in the genetic background of the cultivated tomato L. esculentum (S. lycopersicum), we found that hybrid pollen and seed infertility are each based on 5-11 QTL that individually reduce hybrid fitness by 36-90%. Seed infertility QTL act additively or recessively, consistent with findings in other systems where incompatibility loci have largely been recessive. Genetic lengths of introgressed chromosomal segments explain little of the variation for hybrid incompatibility among NILs, arguing against an infinitesimal model of hybrid incompatibility and reinforcing our inference of a limited number of discrete incompatibility factors between these species. In addition, male (pollen) and other (seed) incompatibility factors are roughly comparable in number. The latter two findings contrast strongly with data from Drosophila where hybrid incompatibility can be highly polygenic and complex, and male sterility evolves substantially faster than female sterility or hybrid inviability. The observed differences between Lycopersicon and Drosophila might be due to differences in sex determination system, reproductive and mating biology, and/or the prevalence of sexual interactions such as sexual selection.

Chromosome Mapping↗

PubMed1979

Genetics of F1 hybrid susceptibility to myeloma grafts.

The genetics of hybrid susceptibility of parental myeloma transplants in histocompatible F1 hybrids was investigated. Various inbred mouse strains and their descendant congenic lines were crossed with BALB/C mice to produce appropriate F1 hybrids. Genetic inferences were drawn from the comparison of the frequencies of tumor graft takes among congenic combinations. Hybrids containing the C57BL/10 genetic background were less susceptible to myeloma transplants than were hybrids of other genotypes. Both H-2-associated and non-H-2-associated genetic factors played significant roles in determining host susceptibility to the transplants. The D end of the major histocompatibility complex did not play a predominant role in determining hybrid susceptibility in C57BL-derived F1 hybrids.

Animals↗

PubMed2003

An integrated approach to optimization of Escherichia coli fermentations using historical data.

Using a fermentation database for Escherichia coli producing green fluorescent protein (GFP), we have implemented a novel three-step optimization method to identify the process input variables most important in modeling the fermentation, as well as the values of those critical input variables that result in an increase in the desired output. In the first step of this algorithm, we use either decision-tree analysis (DTA) or information theoretic subset selection (ITSS) as a database mining technique to identify which process input variables best classify each of the process outputs (maximum cell concentration, maximum product concentration, and productivity) monitored in the experimental fermentations. The second step of the optimization method is to train an artificial neural network (ANN) model of the process input-output data, using the critical inputs identified in the first step. Finally, a hybrid genetic algorithm (hybrid GA), which includes both gradient and stochastic search methods, is used to identify the maximum output modeled by the ANN and the values of the input conditions that result in that maximum. The results of the database mining techniques are compared, both in terms of the inputs selected and the subsequent ANN performance. For the E. coli process used in this study, we identified 6 inputs from the original 13 that resulted in an ANN that best modeled the GFP fluorescence outputs of an independent test set. Values of the six inputs that resulted in a modeled maximum fluorescence were identified by applying a hybrid GA to the ANN model developed. When these conditions were tested in laboratory fermentors, an actual maximum fluorescence of 2.16E6 AU was obtained. The previous high value of fluorescence that was observed was 1.51E6 AU. Thus, this input condition set that was suggested by implementing the proposed optimization scheme on the available historical database increased the maximum fluorescence by 55%.

Algorithms↗

PubMed1984

A mixed population of Trypanozoon in Glossina palpalis palpalis from Ivory Coast.

Cloning trypanosomes clearly showed that at least two enzymically distinct populations of Trypanozoon were present within the salivary glands of a wild-caught Glossina palpalis palpalis from Ivory Coast. Normal sampling techniques detected only the predominant population, which would be the only population reaching a stage suitable for enzyme characterization. Thus a tsetse fly may fail to be implicated as a transmitter of man-infective trypanosomes. The enzymic relationship of the two Trypanozoon populations suggested genetic hybridization. The separate clones retained their individual enzymic integrity after blood and cyclic transmission.

Animals↗

PubMed1991

Studies of the species barrier between Drosophila subobscura and D. madeirensis. I. The genetics of male hybrid sterility.

The genetics of hybrid male sterility between Drosophila subobscura and D. madeirensis were studied with the help of 20 markers in backcross males. A major effect resides in the sex chromosomes: backcross males with the X and Y of different origin (mad X-sub Y or sub X-mad Y) have very small and empty testes. In compatible combinations testes are of normal size but males may be sterile or fertile depending on the genetic constitution of their autosomes. Six autosomal factors affecting hybrid male fertility could be postulated. This estimation is based on the assumption of the absence of interaction between viability and fertility. The presence and the mode of such interaction may modify the number of sterility factors.

Animals↗

PubMed2006

Reinforcement and the genetics of hybrid incompatibilities.

Recent empirical studies suggest that genes involved in speciation are often sex-linked. We derive a general analytic model of reinforcement to study the effects of sex linkage on reinforcement under three forms of selection against hybrids: one-locus, two-locus, and ecological incompatibilities. We show that the pattern of sex linkage can have a large effect on the amount of reinforcement due to hybrid incompatibility. Sex linkage of genes involved in postzygotic isolation generally increases the strength of reinforcement, but only if genes involved in prezygotic isolation are also sex linked. We use exact simulations to test the accuracy of the approximation and find that qualitative predictions made assuming weak selection can hold when selection is strong. Our simulations also show that incompatibilities that evolve in allopatry by drift or weak selection are likely to be lost by swamping during secondary contact, even when selection against hybrids is strong.

Alleles↗

PubMed1989

Regional mapping of the human gene encoding the novel pituitary polypeptide 7B2 to chromosome 15q13----q14 by in situ hybridization.

Genetic sequences encoding the novel pituitary polypeptide 7B2 were isolated from a human pituitary cDNA library. Hybridization analysis of a panel of human x mouse cell hybrids with a 7B2 cDNA probe indicated that the locus for the human 7B2 gene is probably located on chromosome 15. In situ hybridization analysis of metaphase chromosomes allowed the regional localization of the 7B2 gene to chromosome 15 at q13----q14.

Chromosome Mapping↗

PubMed1997

Genetics of hybridization of Glossina swynnertoni with Glossina morsitans morsitans and Glossina morsitans centralis.

Reciprocal crosses were performed with Glossina swynnertoni and Glossina morsitans morsitans and with G.swynnertoni and Glossina morsitans centralis, using strains that carried marker genes in all three linkage groups. Glossina swynnertoni males can inseminate, but not fertilize, G.m.morsitans; all other crosses produced some fertile females. Hybridization did not cause sex ratio distortion among F1 flies. Most F1 and backcross females were fertile, but all F1 males were sterile. Sterility among backcross males was also high (99% in Bx1, 85% in Bx2, and about 50% in Bx3 to Bx5). Chromosome transmission by hybrid females usually conformed to Mendelian expectations, but genetic recombination was lower than observed in G.m.morsitans. The reduction in fertility among backcross females was not associated with heterozygosity in any linkage group. Sterility among hybrid and backcross males was associated with heterozygosity of sex chromosomes and probably autosomes. The results support the systematic placement of G.swynnertoni closer to G.m.centralis than to G.m.morsitans.

Animals↗

PubMed2005

A robust hybrid between genetic algorithm and support vector machine for extracting an optimal feature gene subset.

Development of a robust and efficient approach for extracting useful information from microarray data continues to be a significant and challenging task. Microarray data are characterized by a high dimension, high signal-to-noise ratio, and high correlations between genes, but with a relatively small sample size. Current methods for dimensional reduction can further be improved for the scenario of the presence of a single (or a few) high influential gene(s) in which its effect in the feature subset would prohibit inclusion of other important genes. We have formalized a robust gene selection approach based on a hybrid between genetic algorithm and support vector machine. The major goal of this hybridization was to exploit fully their respective merits (e.g., robustness to the size of solution space and capability of handling a very large dimension of feature genes) for identification of key feature genes (or molecular signatures) for a complex biological phenotype. We have applied the approach to the microarray data of diffuse large B cell lymphoma to demonstrate its behaviors and properties for mining the high-dimension data of genome-wide gene expression profiles. The resulting classifier(s) (the optimal gene subset(s)) has achieved the highest accuracy (99%) for prediction of independent microarray samples in comparisons with marginal filters and a hybrid between genetic algorithm and K nearest neighbors.

Algorithms↗

PubMed1985

Interspecific chloroplast recombination in a Nicotiana somatic hybrid.

Genetic recombination between chloroplasts of two flowering plant species, Nicotiana tabacum and Nicotiana plumbaginifolia, after somatic cell fusion is described. The parental lines differed in three cytoplasmic genetic markers. The N. tabacum mutant SR1-A15 was streptomycin-resistant, defective in chloroplast greening, and lincomycin-sensitive. The N. plumbaginifolia mutant LR400 was streptomycin-sensitive, normal green, and lincomycin-resistant. Streptomycin-resistant clones in cell culture are identified by their ability to form a green callus on a selective medium. Streptomycin resistance in the SR1-A15 mutant could not be expressed due to defective chloroplasts. Protoplasts of the two species were fused, and calli grown from the fused population were screened for the expression of streptomycin resistance from the SR1-A15 line as the result of interspecific chloroplast recombination. A somatic hybrid, pt14, expressed a new combination of the cytoplasmic genetic markers. In the pt14 chloroplast genome three N. tabacum and four N. plumbaginifolia parent specific restriction sites have been identified, indicating that the pt14 chloroplast genome contains at least six recombination sites.

Journal Article↗

PubMed2005

AFLP analyses demonstrate genetic divergence, hybridization, and multiple polyploidization in the evolution of Achillea (Asteraceae-Anthemideae).

Achillea, a temperate genus of herbaceous allogamous perennials, is a model for evolutionary radiation through hybridization and polyploidization. AFLP analyses were performed on 300 individuals of 66 populations and 27 taxa/cytotypes, mainly from the polyploid A. millefolium aggregate and its suspected hybrid links with other clades of the genus. The mosaic genetic structure of hybrids and polyploids is revealed by specific AFLP bands shared with their assumed parents. In E Asia, A. alpina-4x and A. wilsoniana-4x are allotetraploids between A. acuminata-2x (sect. Ptarmica) and A. asiatica-2x (sect. Achillea-A. millefolium agg.). A. virescens-4x is a hybrid species linking A. nobilis agg. and A. millefolium agg. in S Europe. The hybrid swarm A. clypeolata-2x yen A. collina-4x recently formed in Bulgaria shows no AFLP bands additive to its parents; by contrast, other more ancient allopolyploids exhibit genetic innovations. Relationships within A. millefolium agg. are complex. Five 2x-taxa, mostly well separated and regressive, are limited to Eurasia; seven 4x- and 6x-taxa are intimately linked by hybridization, are expansive, and through A. asiatica-2x/4x have formed the N American polyploids. All these results from AFLPs correspond well to other evidence, and indicate a long history of reticulate evolution in Achillea.

Achillea↗