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At least 19 recordsLinked to original sources
PubMed1982

Protein polymorphisms, segregation in genetic crosses and genetic distances among fishes of the genus Xiphophorus (Poeciliidae).

The products of 49 protein-coding loci were examined by starch gel electrophoresis for populational variation in six species of Xiphophorus fishes and/or segregation in intra-and interspecific backcross and intercross hybrids. Electrophoretic variation was observed for 29 of the 35 locus products in a survey of 42 population samples. The highest frequency of polymorphic loci observed in noninbred populations was 0.143. After ten or more generations of inbreeding, all loci studied were monomorphic. Inbred strains generally exhibited the commonest electrophoretic alleles of the population from which they were derived. An assessment of genetic distances among Xiphophorus populations reflected classical systematic relationships and suggested incipient subspeciation between X. maculatus from different drainages as well as several species groups. Thirty-three loci were analyzed with respect to segregation in hybrids. The goodness of fit of segregations to Mendelian expectations at all loci analyzed (except loci in linkage group I) is interpreted as evidence for high genetic compatibility of the genomes of Xiphophorus species. It is anticipated that these data will result in a rapid expansion of the assignment of protein-coding loci to linkage groups in these lower vertebrate species.

Alleles↗
PubMed1992

An RFLP map of the Plasmodium falciparum genome, recombination rates and favored linkage groups in a genetic cross.

We report a genetic linkage map of the Plasmodium falciparum genome, using the inheritance patterns of nearly 90 RFLP markers in a genetic cross. Markers were assigned to polymorphic loci on all 14 nuclear chromosomes. Genetic recombination between parental markers was detected in each of the progeny, indicating that progeny from cross-fertilization events were favored over progeny from self-fertilization of either parent alone. Inheritance patterns among the markers suggested that certain parental linkage groups on chromosomes 2, 3, 12 and 13 were favored in the cross. Recombination frequencies on five chromosomes indicated an approximate map unit size of 15-30 kb per centiMorgan for P. falciparum.

Animals↗
PubMed1987

A histidine-rich protein gene marks a linkage group favored strongly in a genetic cross of Plasmodium falciparum.

Two histidine-rich protein genes in Plasmodium falciparum are related by an ancestral duplication and interchromosomal transposition. We have followed the inheritance of these genes in a cross between two clones of P. falciparum. Examination of progeny shows that one gene, encoding the protein HRP-II, behaves as expected and may be inherited from either parent. The other gene, encoding HRP-III, has been found to derive from one parent in all progeny examined. We conclude the linkage group marked by HRP-III is favored strongly in the cross. This linkage group spans a region at one end of chromosome 13. Growth studies suggest the favored inheritance is explained by rapid expansion of progeny possessing the HRP-III marker relative to slower growth of progeny without it.

Chromosome Mapping↗
PubMed1994

Analysis of a new genetic cross between two East African Trypanosoma brucei clones.

Two clones of East African Trypanosoma brucei, with distinct homozygous isoenzyme patterns for one of three enzymes examined, were cotransmitted through the tsetse fly vector Glossina morsitans centralis. Flies with mature infections were individually fed on mice and the subsequent bloodstream from populations analysed for the presence of hybrid trypanosomes by isoenzyme analysis. Several combinations have previously been detected using this approach (Schweizer, Tait & Jenni, 1988; Sternberg et al. 1989). Four clones were isolated from one of the hybrid-containing populations. They showed a hybrid phenotype, as would be expected for the F1 progeny in a diploid Mendelian system. The analysis of the progeny clones, using two gene probes which detect restriction fragment length polymorphisms between the two parental stocks, showed that alleles had segregated at each locus and given rise to three different non-parental combinations of alleles in the hybrid progeny. Characterization of the hybrid progeny clones by PFGE (pulsed field gradient gel electrophoresis) revealed that all progeny clones were recombinant for the intermediate size chromosomes. From the analysis of the segregation of the larger chromosomes, marked by PGK (phosphoglycerate kinase) and CP (cysteine protease) gene probes, it was inferred that the progeny clones did not result from a direct fusion of diploid cells. Results with the PGK probe fit into a classical system with meiosis and subsequent fusion of the nuclei to form diploid progeny. On the other hand, blots with the CP probe as well as some of the ethidium bromide stained PFGE gels revealed the existence of non-parental size chromosomes in some of the hybrid progeny. This phenomenon was observed previously (Gibson, 1989) and further investigation is required to elucidate the mechanism.

Africa, Eastern↗
PubMed1979

Expression of xenotropic murine leukemia viruses as cell-surface gp70 in genetic crosses between strains DBA/2 and C57BL/6.

Flow microfluorometry was used to assess levels of xenotropic murine leukemia virus envelope-related cell-surface antigens (XenCSA) expressed on lymphocytes of mice derived from crosses between C57BL/6 (B6) and DBA/2 (D2); 24 recombinant inbred strains (BXD RIs) and 62 backcross mice were studied. The results suggest that XenCSA expression is affected by more than one gene but that the predominant influence is exerted by a single semidominant gene apparently located on chromosome 4 at or in close proximity to the Fv-1 locus. Studies of spontaneous virus production in B6D2F1 X D2 mice suggest that this locus may also affect production by spleen cells of xenotropic MuLV registering in a fluorescent antibody assay of mink lung cells.

Animals↗
PubMed1997

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

In the order Kinetoplastida, genetic exchange has been demonstrated only in the genus Trypanosoma. Analysis of kinetoplast DNA (kDNA) in genetic crosses of T. brucei has shown that whereas maxicircles are inherited uniparentally, minicircles are inherited from both parents. This result was confirmed for a new cross of T. b. brucei and T. b. rhodesiense by restriction enzyme digestion and Southern analysis of purified kDNA. By hybridisation with small minicircle-derived probes, we could demonstrate the presence of particular parental minicircles in the kDNA of hybrid progeny clones. All hybrid clones had inherited two minicircles from one parent despite two of the four clones having maxicircles from the other parent. The results suggest that rather than small-scale exchange of minicircles between parental networks, gross breakdown and reassembly of the minicircle network occurs during genetic exchange.

Animals↗
PubMed2026

Methods for single-pair Ascaridia galli genetic crosses.

Ascarid parasites infect a wide range of hosts, causing significant clinical and economic impacts. However, genetic tools for studying ascarid biology remain limited. We optimized genetic crosses using Ascaridia galli , a common ascarid of chickens. Sexually immature larval parasites were recovered from donors, transferred to gelatin capsules, and then given orally to recipients. We successfully established single-pair matings in 32% of crossing attempts. This method to control genetic crosses further establishes the avian model for ascarid research and will enable future studies to create a high-quality reference genome, inbreed anthelmintic resistant and sensitive lines, and investigate host-pathogen interactions.

Journal Article↗
PubMed1964

RECIPIENT ABILITY OF SALMONELLA TYPHOSA IN GENETIC CROSSES WITH ESCHERICHIA COLI.

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Stanley Falkow, and L. S. Baron. Recipient ability of Salmonella typhosa in genetic crosses with Escherichia coli. J. Bacteriol. 87:54-60. 1964.-Salmonella typhosa strain 643WS(r) was mated with Escherichia coli Hfr strains W1895 and Hayes, with single marker selection for the E. coli genes lac(+) (lactose utilization) and ara(+) (arabinose utilization). Four classes of Salmonella hybrids were obtained, each class possessing one marker derived from one E. coli parent. In a series of eight genetic crosses, in which each hybrid class was remated with each of the Hfr strains, recipient ability of the hybrids was increased only when their substituted E. coli genetic section matched the lead region of the Hfr chromosome. Data obtained from replica plating indicated that the S. typhosa 643WS(r) population is probably homogeneous with respect to its initial ability to mate with E. coli. Transfer of the F-lac element was found to occur only slightly less efficiently from an E. coli F' donor to S. typhosa than it did to an E. coli F(-) strain. This indicated that E. coli is able to conjugate almost as effectively with S. typhosa as it does intraspecifically. However, failure to detect beta-galactosidase production by merozygotes derived from an E. coli Hfr W1895 x S. typhosa mating indicated that transfer of chromosomal lac(+) may be impaired.

Arabinose↗
PubMed2004

GenomeMixer: a complex genetic cross simulator.

UNLABELLED: GenomeMixer is a cross-platform application that simulates meiotic recombination events for large and complex multigenerational genetic crosses among sexually reproducing diploid species and outputs simulated progeny to several standard mapping programs. AVAILABILITY: Documentation, C++ source, and binaries for Mac OS X and x86 Linux are freely available at http://www.nervenet.org/genome_mixer/. GenomeMixer can be compiled on any system with support for the Trolltech Qt toolkit, including Windows.

Chromosome Mapping↗
PubMed1983

Toxoplasma gondii: genetic crosses reveal phenotypic suppression of hydroxyurea resistance by fluorodeoxyuridine resistance.

Mutants resistant to sinefungin (SF) and hydroxyurea (HU) were isolated from an oocyst-producing strain of Toxoplasma gondii with the aid of mutagenesis with ethylnitrosourea. These mutants were used with previously described mutants resistant to adenine arabinoside (araA) and fluorodeoxyuridine (FUDR) in genetic crosses in cats. In order to interpret the data from crosses in which all four mutants were used to infect the same cat, it was necessary to devise a mathematical expression to predict the recombination frequency for unlinked markers. This frequency was shown in theory to be half of the product of the two parental phenotype frequencies. A series of crosses in which the parental frequencies were systematically varied yielded frequencies of recombination that were in accord with this calculation. The four-way crosses in the same cat showed unlinked recombination between all markers except HU and FUDR. This pair of markers yielded no doubly resistant recombinants, suggesting complete linkage. However, linkage was excluded when a binary cross between the HU- and FUDR-resistant mutants resulted in the normal number of doubly sensitive recombinants. The lack of doubly resistant recombinants was shown to be a consequence of phenotypic suppression of HU resistance by FUDR resistance. This suppression was first demonstrated by showing that an FUDR-resistant mutant selected from an HU-resistant parasite lost the HU resistance. The phenotypically suppressed HU-resistant gene was revealed by genetic crosses with wild type T. gondii. Although both parental stains were sensitive to HU, some of the progeny parasites were resistant.

Animals↗
PubMed2000

EBL-1, a putative erythrocyte binding protein of Plasmodium falciparum, maps within a favored linkage group in two genetic crosses.

The Duffy binding-like (DBL) superfamily of Plasmodium falciparum encompasses genes which encode ligands for host cell receptors. This superfamily includes two distinct groups of genes, the var genes which encode antigenically variant cytoadherence proteins (PfEMP1), and the eba-175 gene which encodes a glycophorin A binding protein involved in erythrocyte invasion. Here we describe another DBL superfamily member related to eba-175, the ebl-1 gene. Like the eba-175 gene, ebl-1 is a single copy gene encoding DBL domains that have sequences and an overall arrangement distinct from var genes. The inheritance of ebl-1 was found to be strongly favored in two genetic crosses in which one parental clone lacked a chromosome segment carrying the gene. A proliferation phenotype has been previously linked to the same chromosome segment in the first genetic cross. These results suggest that ebl-1 and eba-175 are related members of a multigene family involved in the invasion of erythrocytes by P. falciparum.

Amino Acid Sequence↗
PubMed1986

Emotional reactivity and alcohol preference among genetic crosses of the Maudsley and Roman rats.

The relationship between open-field emotional reactivity and alcohol preference was investigated in crosses of the Maudsley and Roman rat lines. No significant differences were found in any of the behaviors between the respective reciprocal crosses. The scores on the two variables showed a positive correlation between open-field defecation (OFD) and alcohol preference. The findings confirmed a prediction for the relationship between OFD and alcohol preference in these genetic crosses. In light of the previous findings it would seem that OFD and alcohol preference are not directly related to each other, and emotional reactivity acts as a mediating process between the two behaviors. However, in these genetic crosses the observed relationship between OFD and alcohol preference can be explained by a possible genetic overlap between the mechanisms mediating these two behaviors.

Alcohol Drinking↗
PubMed1995

Trypanosoma brucei: inheritance of kinetoplast DNA maxicircles in a genetic cross and their segregation during vegetative growth.

The inheritance of maxicircle DNA was determined using a polymorphic EcoRI restriction site in the maxicircle variable region. In 11 hybrid progeny from a genetic cross of two stocks of Trypanosoma brucei, 7 progeny apparently inherited maxicircles uniparentally from either parent, in agreement with the results from previous studies, but in 4 progeny inheritance was biparental. Three subclones from 2 of these 4 progeny were made, and in these the maxicircles of only one parental type were detected. These data are considered in terms of a simple model whereby half the maxicircle genomes are inherited from each parent into progeny at meiosis with subsequent stochastic segregation at each mitotic division. This model generates a quantitative prediction as to the period of time required for fixation of inheritance to a uniparental pattern which provides a reasonable fit to the experimental data. These results provide an explanation as to why previous studies have shown that maxicircles are (apparently) inherited uniparentally: the kinetoplast is a unitary organelle inherited faithfully at cell division, but the maxicircles that it contains are best considered as a population that divides stochastically. Consideration of the model also explains why maxicircle populations are homogeneous.

Animals↗
PubMed2000

Do-it-yourself statistics: A computer-assisted likelihood approach to analysis of data from genetic crosses.

Graduate school programs in genetics have become so full that courses in statistics have often been eliminated. In addition, typical introductory statistics courses for the "statistics user" rather than the nascent statistician are laden with methods for analysis of measured variables while genetic data are most often discrete numbers. These courses are often seen by students and genetics professors alike as largely irrelevant cookbook courses. The powerful methods of likelihood analysis, although commonly employed in human genetics, are much less often used in other areas of genetics, even though current computational tools make this approach readily accessible. This article introduces the MLIKELY.PAS computer program and the logic of do-it-yourself maximum-likelihood statistics. The program itself, course materials, and expanded discussions of some examples that are only summarized here are available at http://www.unisi. it/ricerca/dip/bio_evol/sitomlikely/mlikely.h tml.

Animals↗