PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Hybridization, Genetic”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1991

Genetic hybrids of Plasmodium falciparum identified by amplification of genomic DNA from single oocysts.

Individual oocysts from Plasmodium falciparum-infected Anopheles gambiae and Anopheles stephensi mosquitoes have been examined by the PCR technique, after their removal from the midgut. The DNA obtained from these oocysts has been amplified using oligonucleotide primers specific for part of the merozoite surface antigen MSA-1 gene. This technique distinguishes oocysts which are the products of self-fertilisation events from those which are the products of cross-fertilisation between different parasite clones.

Animals↗
PubMed1990

Kinetoplast DNA minicircles are inherited from both parents in genetic hybrids of Trypanosoma brucei.

We have examined the inheritance of kinetoplast DNA (kDNA) in gentic crosses of trypanosomes. In 2 independent crosses of Trypanosoma brucei spp. trypanosomes, the kDNA maxicircles which carry the genes for mitochondrial biogenesis, were inherited from one parent only, as already found by other workers. However, the other component of kDNA, the minicircles, were inherited from both parents. This was demonstrated by Southern analysis using cloned minicircle probes. The inheritance of kDNA is therefore not uniparental. Our data point to fusion of the parental kinetoplast DNA networks during genetic exchange, with gradual loss of one or other parental maxicircle type due to random segregation of maxicircles at subsequent mitotic divisions. We infer that the first event of genetic exchange is fusion of parental trypanosomes (either haploid or diploid), followed at some point by fusion of the parental mitochondria.

Animals↗
PubMed1975

Genetic hybridization at the unlinked thy and str loci of Streptococcus.

The sanguis and pneumoniae species of Streptococcus were used as recipients in transformations from str+ to str-r and from thy- to thy+. The str-r mutations in the two species had been previously shown to be allelic. Homology of the thy- mutations in the two species was demonstrated in the similar phenotypic properties they conferred (death in the absence of thymidine, lack of thymidylate synthetase). The str and thy loci are unlinked in each species.--- When the two species are transformed by both homospecific and heterospecific DNA, the efficiency is always lower in the heterospecific cross. The efficiency of heterospecific transformation is considerably lower at the thy than at the str locus. DNA was extracted from recipients that had integrated markers of heterospecific origin. When such hybrid DNA is tested on the original recipient species, the heterospecific markers are usually as efficient as homospecific markers. When tested on the original donor species, however, the hybrid DNA is usually more efficient than heterospecific DNA. This is true for both thy and str transformation. -- -- Forty independent thy+ hybrids were obtained in the cross of sanguis thy- recipients with pneumoniae thy+ DNA. These hybrids fall into a number of classes based upon the relative efficiency with which their extracted DNA's are able to transfer the thy+ marker into pneumoniae thy- cells. The most efficient of these DNA's exhibits about 20% of the efficiency of homospecific pneumoniae thy+ DNA and three orders of magnitude greater efficiency than heterospecific sanguis thy+ DNA. Thus, very little of the inefficiency of heterospecific transformation of the thy locus is ascribable to a classic restriction mechanism. Rather, the wild-type thy+ loci in the two species appear to differ at multiple sites, and independent heterospecific transfers result in differential extents of integration of these sites. On this basis, the thy+ loci of the two species differ at a greater number of sites than do the respective str+ loci.

Alleles↗
PubMed1976

Genetic hybridization of the leu-ilv region in bacilli.

Two auxotrophic strains of Bacillus subtilis 168 served as recipients for DNA extracted from various wild-type strains of B. subtilis and wild-type species of the genus Bacillus. Depending upon the DNA source, heterologous transformations of the linked try-his-tyr loci were either as efficient as those observed with donor DNA obtained from the wild type B. subtilis 168 strain or were undetectable. The order and relative distances of the three gene loci were the same for all active DNA preparations. Similar results were obtained in heterologous transformations of the linked leu-ilv loci, except that DNA preparations from the Bacillus globigii and B. subtilis var. niger species exhibited a reduced but detectable frequency of transformation. With the latter preparations a marked polarity of integration favouring the leu+ gene was observed, an effect not seen with homologous DNA. Six independent hybrid lines were obtained from transformation of B. subtilis leu- ilv- with DNA from B. subtilis var. niger leu+ ilv+. DNA extracted from these lines fell into two classes on the basis of activity in transforming the parental recipient strain: (i) indistinguishable from homologous DNA, and (ii) intermediate between homologous DNA and DNA from the original donor strain. With either class, polarity of integration was no longer observed in the leu-ilv region. The intermediate type of hybrid demonstrates that at least some of the inefficiency of heterospecific transformation must be due to heterology in nucleotide sequence between the different species at the leu-ilv loci.

Bacillus↗
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↗
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↗
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↗
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↗
PubMed1990

Overexpression of matrix Gla protein mRNA in malignant human breast cells: isolation by differential cDNA hybridization.

Genetic alterations are involved in the development of human breast cancer. We sought to isolate genes that are differentially expressed or suppressed in cultured human breast carcinoma cells as compared to cultured normal human breast epithelial cells by employing differential screening of selected cDNA libraries. Analysis of several clones thus isolated revealed that the matrix Gla protein (MGP) gene is overexpressed in the breast cancer cell line 600 PEI, though is transcribed at lower levels in most other mammary derived cultures. MGP requires vitamin K dependent gamma-carboxylation for its known function and thus can be inhibited by vitamin K antagonists. This raises the possibility that MGP may be among those factors that when inhibited by vitamin K antagonists reduce metastases in experimental models. Among the gene whose transcription is consistently suppressed upon mammary transformation were fibronectin and the type I keratin, K14. Differential cDNA screening therefore is an effective method of identifying genes involved in various aspects of mammary cell transformation.

Base Sequence↗
PubMed1988

Packaging specific segments of the Salmonella chromosome with locked-in Mud-P22 prophages.

Hybrid genetic elements, Mud-P and Mud-Q (collectively, Mud-P22s), have been constructed that carry two-thirds of the temperate Salmonella phage P22 genome sandwiched between the ends of transposon Mu. Insertions of these elements in the Salmonella chromosome generate locked-in P22 prophages that cannot excise. Upon induction (as a consequence of the inactivation of P22 c2 repressor), a locked-in prophage replicates its DNA in situ, resulting in the amplification of neighboring regions of the chromosome and the processive packaging of three contiguous headsful of adjacent DNA in one direction from the P22 packaging site, pac. Phage particles in an induced lysate of a Mud-P22 lysogen contain DNA molecules corresponding to several minutes of chromosomal DNA adjacent to the site of prophage insertion and transduce nearby genetic markers with high efficiencies. Mud-P22 prophages have been introduced into an F' episome by transposition; resident Mud insertions on the Salmonella chromosome may be converted to Mud-P22 insertions by homologous recombination in P22-mediated transductional crosses.

Chromosomes, Bacterial↗
PubMed1975

Human intraspecific somatic cell hybrids: a genetic and karyotypic analysis of crosses between lymphocytes and D98/AH-2.

A number of human intraspecific hybrids were produced by fusing the 8-azaguanine-resistant cell line D98/AH-2 with PHA-stimulated lymphocytes from a normal human male, followed by selection in HAT medium. The parent cells differed in zymogram patterns for 4 enzyme systems. Hypoxanthine-guanine phophoribosyltransferase was missing in D98/AH-2 and was determined in the hybrids by the normal gene derived from the lymphocyte donor's X chromosome. The HL-A antigens of the lymphocyte donor as well as the W28 specificity from HeLa were easily recognized by a cytotoxicity assay on the hybrid cells, while D98/AH-2 itself was not killed in the normal way by any HL-4 typing sera. The initial hybrid karyotype in all lines was relatively stable, but slow loss of chromosomes occurred following extended growth in culture. The importance of the culture conditions for the rate of chromosome loss was demonstrated. The behavior of several chromosomes was followed in the hybrids and their derivatives. There was relatively nonspecific loss of small numbers of chromosomes, showing that loss of chromosomes from both the D98/AH-2 and the normal lymphocyte parent can occur. Cell lines resistant to 6-thioguanine were selected from the sensitive hybrids. Most had lost the lymphocyte donor's X chromosome, thereby losing the only active allele for HGPRT present in the initial hybrids. However, one line, DMR41, apparently retained the X chromosome and may have a mutated allele for HGPRT. Two lines that are the products of spontaneous segregation are also described. DM4CS and DM17A.

Acid Phosphatase↗
PubMed1985

Application of monoclonal antibodies and genetically-engineered hybrid B-subunit proteins to the analysis of the cholera/coli enterotoxin family.

Single amino acid substitutions, introduced by genetic engineering, significantly modify the behavior of the B-subunits of the cholera/coli enterotoxin family in SDS-PAGE and also markedly affect the reactivity of the proteins with mouse hybridoma-derived monoclonal antibodies raised against H-LT. The results indicate that single amino acids play an important role in defining epitopes in these proteins.

Amino Acid Sequence↗
PubMed1978

Genetic characterization of Mu-like bacteriophage D108.

Infection of Escherichia coli by bacteriophage D108 was shown to result in the generation of apparently random chromosomal mutations. Approximately 1% of the cells lysogenized by D108, as with Mu, acquired new auxotrophic mutations. D108-induced mutations were nonreverting and were most probably the result of insertion of the D108 genome into regions of genetic function. D108 and Mu shared many similar properties but were heteroimmune and had different host ranges. Lytic infections of Mu lysogens with D108 and D108 lysogens with Mu resulted in 100-fold increases in release of phage with prophage markers over those due to spontaneous induction. Phenotypic mixing was common, with most phage carrying the prophage immunity being packaged in particles with the host range of the superinfecting phage. A fraction of the superinfecting phage genomes were, however, packaged in particles with the prophage-specified host range. Although 10% of the prophage progeny were D108-Mu genetic hybrids, superinfecting phage-induced release of the prophage with reciprocal phenotypic mixing occurred in recA hosts, in which the frequency of D108-Mu genetic hybrids was reduced 100-fold.

Coliphages↗
PubMed1991

Substrate recognition by the NIa proteinase of two potyviruses involves multiple domains: characterization using genetically engineered hybrid proteinase molecules.

The proteolytic activity associated with the small nuclear inclusion protein (NIa proteinase) of tobacco etch virus (TEV), a potyvirus, catalyzes several cleavages at sites within the polyprotein derived from the TEV RNA genome. The homologous proteinase of tobacco vein mottling virus (TVMV), a closely related potyvirus, cleaves at similar, yet distinct, recognition sites. We examined these proteinases, in a cell-free cleavage system, in an attempt to define the biochemical basis of substrate specificity. Each proteinase was specific for its own cleavage site sequence in cell-free trans processing reactions, and no processing of the heterologous cleavage site was evident. Domains of the proteinase which were important in determining this substrate specificity were identified by generating hybrid proteinase genes containing both TEV and TVMV NIa proteinase coding sequences. Using site-directed mutagenesis and standard recombinant DNA techniques, plasmids were constructed which contained coding sequences for hybrid TEV-TVMV proteinases. These plasmids were expressed and tested in a cell-free environment for their ability to cleave both TEV and TVMV substrates. The data suggest that the carboxy-terminal 150 amino acids of the NIa protein contain the necessary information to specifically recognize a particular cleavage site sequence, and that specificity determinants are contained in at least three interactive subdomains within this region.

Amino Acid Sequence↗
PubMed1985

Alloreactive cytolytic T-cell clones preferentially recognize conformational determinants on histocompatibility antigens: analysis with genetically engineered hybrid antigens.

Hybrid genes were constructed for the localization of allodeterminants on murine class I antigens recognized by antibodies and cytolytic T lymphocytes. By using deletion subclones of the H-2Kd and H-2Kk genes, homologous regions were exchanged between the two alleles. The altered genes were introduced and expressed in mouse fibroblast and fibrosarcoma cells. Cells expressing hybrid antigens were analyzed with 29 monoclonal anti-H-2Kd and anti-H-2Kk antibodies and with 150 short-term alloreactive cytolytic T-cell clones. When only the first or only the second amino-terminal domain was exchanged, most T cells and 60% of the antibodies lost their reactivity to the H-2K antigen. No T-cell clone was directed against the third extracellular domain, whereas three antibodies could bind to this domain. This implies that nearly all determinants essential for a cytolytic T-cell response or for antibody binding lie on the two external domains and are conformational structures generated by the interaction of these two domains.

Animals↗
PubMed1977

Genetic studies of hybrids between coliphage lambda and salmonella phage P22: genetic analysis of the P22-lambda hybrid class.

P22-lambda hybrids which retain the protein coat of P22 have been isolated and characterized into two types. Type 1 hybrids which have the c through O-P genes of lambda are unable to grow lytically on Salmonella typhimurium. On the other hand, type 2 hybrids which contain only the c region of lambda, plated on S. typhimurium. Both hybrid types retained the generalized transducing and antigenic conversion capabilities of P22.

Antigens, Viral↗
PubMed1991

Studies of the species barrier between Drosophila madeirensis and Drosophila subobscura. II. Genetic analysis of developmental incompatibilities in hybrids.

The genetic analysis of two abnormal characters, extra sex combs and abnormal head shape in hybrids between Drosophila madeirensis and Drosophila subobscura, revealed a major effect of the X chromosome in both cases. Autosomes also play a role in determining these abnormalities, the E chromosome in case of extra sex combs, the E and O chromosomes in case of abnormal head shape. Autosomes do not cause the two abnormal characters, without interacting with the X chromosome.

Animals↗