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PubMed2002

[Segregation distortion of marker nuclear genes in alloplasmic and isoplasmic lines of barley].

Inheritance of barley nuclear genes responsible for various morphological marker traits was studied in hybrid populations F2 and Fa. Nine marker genes showed deviation from Mendelian monogenic inheritance depending on the cross direction and maternal cytoplasm. Segregation biases to both recessive mutant and dominant normal phenotypes were observed. Mechanisms of the segregation bias related to cytoplasm substitution in iso- and alloplasmic lines are discussed.

Cell Nucleus↗
PubMed2002

Co-segregation of thrombophilic disorders in factor V Leiden carriers; the contributions of factor VIII, factor XI, thrombin activatable fibrinolysis inhibitor and lipoprotein(a) to the absolute risk of venous thromboembolism.

BACKGROUND AND OBJECTIVES: The clinical expression of factor V Leiden varies widely within and between families and only a minority of carriers will ever develop venous thromboembolism. Co-segregation of thrombophilic disorders is a possible explanation. Our aim was to assess the contributions of high levels of factor VIII:C, factor XI:C, thrombin activatable fibrinolysis inhibitor (TAFI) and lipoprotein (a) (Lp(a)) to the risk of venous thromboembolism in factor V Leiden carriers. DESIGN AND METHODS: Levels of the four proteins were measured, in addition to tests of deficiencies for antithrombin, protein C and protein S, and the prothrombin G20210A mutation, in 153 factor V Leiden carriers, derived from a family cohort study. The (adjusted) relative risk and absolute risk of venous thromboembolism for high levels of each protein were calculated. RESULTS: Of carriers, 60% had one or more concomitant thrombophilic disorders. Crude odds ratios (95% CI) of venous thromboembolism for high protein levels were: 3.2 (1.1-9.3) (factor VIII:C); 1.7 (0.6-4.9) (factor XI:C); 3.0 (1.1-8.2) (TAFI); and 1.9 (0.7-5.7) (Lp(a)). Adjusted for age, sex, other concomitant thrombophilic disorders and exogenous risk factors, the odds ratio for venous thromboembolism were 2.7 (0.8-8.7) for high factor VIII:C levels and 1.8 (0.6-5.3) for high TAFI levels. Annual incidences in subgroups of carriers were 0.35% (0.09-0.89), 0.44% (0.05-1.57) and 0.94% (0.35-2.05) for concomitance of high levels of factor VIII:C, TAFI and both, respectively, as compared to 0.09% (0.00-0.48) in single factor V Leiden carriers and 1.11% (0.30-2.82) for other concomitant disorders. INTERPRETATION AND CONCLUSIONS: High levels of factor VIII:C and TAFI, in contrast with factor XI:C and Lp(a), are mild risk factors for venous thromboembolism, and substantially contribute to the risk of venous thromboembolism in factor V Leiden carriers. Our data support the hypothesis that the clinical expression of factor V Leiden depends on co-segregation of thrombophilic disorders.

Adult↗
PubMed2002

Identification of gene expression profiles that segregate patients with childhood leukemia.

To identify genes whose expression correlated with biological features of childhood leukemia, we prospectively analyzed the expression profiles of 4608 genes using cDNA microarrays in 51 freshly processed bone marrow samples from children with acute leukemia, over a 24-month period, at a single institution. Two supervised methods of analysis were used to identify the 20 best discriminating genes between the following cohorts: acute myelogenous leukemia (AML) versus acute lymphoblastic leukemia (ALL); B-lineage versus T-lineage ALL; newly diagnosed B-lineage standard-risk versus high-risk ALL; and B-lineage leukemia harboring the TEL-AML 1 fusion versus patients without a molecularly characterized translocation. These methods identified overlapping sets of genes that segregated patients within described subgroups. Cross-validation demonstrated that the majority of patients could be correctly classified based on these genes alone, and hierarchical clustering grouped patients with similar clinical and biological disease features. The potential for select genes to discriminate patients was validated using real-time PCR in samples that were analyzed by microarray profiling and in other uniformly processed leukemic marrow samples. As expected, microarray technology can successfully segregate patients defined by traditional measures such as immunophenotype and cytogenetic alterations. However, among specific subgroups, this preliminary analysis also suggests that microarrays can identify unanticipated similarities and diversity in individual patients and thus may be useful in augmenting risk-group stratification in the future.

Child↗
PubMed2002

Morphological, cytological and BSA-based testing on limited segregation population AFLPs.

Cytoplasmic male sterility (cms) in rye (Secale cereale L.), especially cytoplasma PAMPA, is used commercially in hybrid breeding programmes. The development of molecular markers that are tightly linked to the numerous genes coding for pollen fertility is expected to have great impact in the field. Morphological and cytological analyses of plants from a three-way cross C394: [(S67P/94 x S38/94) x CHD296] indicated the presence of at least several genes acting at different stages of pollen grain development, and proved the concurrence of both approaches in plant classification. The AFLP technique combined with the Bulk Segregant Analysis (BSA) were applied to identify DNA fragments linked to the genes of interest. All the 256 possible primer pair combinations based on the MseI and EcoRI restriction sites generated distinct band patterns allowing the identification of 31143 DNA fragments, visualised using the isotopic method. On average, any given primer combination generated 122 fragments. Among 1111 and 431 potential genetic markers respectively identified in the restorer form and the maternal lines, 775 and 295 were present in the F2 population. These numbers were then reduced to 109 and 51. The identified DNA fragments were tested on a limited segregating population, C394-F2, in order to eliminate false signals and to select markers for a future marker-assisted selection programme. Twenty-five markers were selected. Four of these markers were not identified via the BSA approach, indicating that if a highly polymorphic component is used for a cross, or a polygenic trait is studied, then the use of a limited population may be required.

Breeding↗
PubMed2003

Abnormal segregation of prion protein octapeptide-repeat alleles in cattle.

The study was conducted on full-families of Black-and-White cattle obtained as 25 AI sire families and 355 cows, as well as their progenies, mostly heifers at the age of 1-3 months. The sire group was composed by the casual qualification of 10 PRNP 6/6 and 15 PRNP 6/5 individuals on the basis of accessible young progenies. The randomly selected group of cows is characterised by a very high frequency of PRNP 6/6 (74.9%), followed by lower frequency of PRNP 6/5 (24.5%) and a very low frequency of PRNP 5/5 genotype (0.6%). The progenies represent all expected genotypes, such as: PRNP 6/6 (60.5%), PRNP 6/5 (35.8%) and PRNP 5/5 (3.7%), respectively. Taking into consideration the genotypes of parents and progenies, the segregation of PRNP 6 and PRNP 5 alleles was analysed. Results of the non-informative mating variant of male symbol PRNP 6/6 x female symbol PRNP 6/6 (n = 87) are affected by the PRNP 6/6 progeny genotype in all cases. Subsequently, the results of mating variants male symbol PRNP 6/6 x female symbol PRNP 6/5 (n = 29) and male symbol PRNP 6/5 female symbol PRNP 6/6 (n = 179) showed statistically non-significant differences in both above-mentioned alternations. The progeny group related from male symbol PRNP 6/5 x female symbol PRNP 6/5 parental mating obtained fully informative and most valuable results based on the presented research concept. In the common group of 58 calves, the genotype PRNP 6/6 is represented by 26 individuals (44.8%), PRNP 6/5 - by 19 individuals (32.8%) and PRNP 5/5 - by 13 individuals (22.4%). Therefore, the theoretical genotype rate (25% : 50% : 25%) is drastically deformed and the differentiation between the observed and expected numbers of animals is statistically highly significant (chi(2) = 12.72; 2 df.). These differences are affected by two times higher PRNP 6/6 homozygous (chi(2) = 9.12; 1 df.) and responsively by the low number of PRNP 6/5 heterozygous animals (chi(2) = 3.45; 1 df.). Further investigations are carried out to explain the genetic determination of abnormal PRNP octa-peptide repeat allele segregation, which suggests possible lethal cis-trans linkage effects.

Animals↗
PubMed1992

Segregation of structural collagen genes in adolescent idiopathic scoliosis.

The etiology of idiopathic scoliosis remains unknown. The condition results in a characteristic deformity of the spine and surrounding tissues. Both Types I and II collagen are important constituents of the affected tissues, and thus defective collagens are reasonable candidates for the primary abnormality in adolescent idiopathic scoliosis (AIS). Direct analyses of the amount and solubility of collagen have revealed differences between normal individuals and those with AIS. However, these changes may be secondary to the mechanical effects of the spinal deformity. Segregation analysis was done of genetic markers linked to the structural genes encoding Types I and II collagen to test these candidate loci in four pedigrees with dominantly inherited AIS. In one pedigree, markers linked to both of the Type I collagen loci (COL1A1 and COL1A2) were found to be inherited independently of the abnormal phenotype. Two pedigrees were discordant at one of the Type I loci. The condition also segregated independently of the locus for Type II collagen (COL2A1) in three pedigrees. This is evidence against idiopathic scoliosis generally being caused by mutations in the Types I and II collagen genes.

Adolescent↗
PubMed1992

Discordant segregation of Na+,K(+)-adenosine triphosphatase alleles and essential hypertension.

OBJECTIVES: To determine whether the alpha 2 and or beta 1 isoforms of the Na+,K(+)-adenosine triphosphatase (Na+,K(+)-ATPase) are involved in the pathogenesis of essential hypertension. DESIGN: Segregation analysis of polymorphic DNA markers was used to test the involvement of Na+,K(+)-ATPase in essential hypertension. PARTICIPANTS: Children with persistent hypertension having one parent with essential hypertension were included in the study. Criteria for persistent hypertension were blood pressure readings with systolic and/or diastolic levels exceeding the 95th percentile based upon age and sex. The diagnosis of hypertension for adults, including parents and older siblings, was confirmed using criteria recommended in the 1988 report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure. RESULTS: In three essential hypertensive families consisting of 18 members including 11 hypertensives, several obligate recombinants between the Na+,K(+)-ATPase alpha 2 isoform marker and the hypertension phenotype were observed. Similarly, in one hypertension family consisting of four members, obligate recombinants between the beta 1 isoform marker and the disease were observed. CONCLUSIONS: The discordant segregation of the alpha 2 and beta 1 isoform markers and essential hypertension suggests that neither the Na+,K(+)-ATPase alpha 2 nor beta 1 isoform genes play a primary role in the pathogenesis of hypertension in the families studied.

Adult↗
PubMed2003

Segregation analysis of 231 Ashkenazi Jewish families for evidence of additional breast cancer susceptibility genes.

Between 5 and 10% of breast cancer is attributable to inherited cancer susceptibility genes. Mutations in the genes BRCA1 and BRCA2 account for two-thirds of hereditary breast cancer cases. Using segregation analysis, families of cases without BRCA1/2 mutations were studied for statistical evidence of another major breast cancer gene in a community-based sample of Jewish probands tested previously for the presence of three BRCA founder mutations. A total of 231 probands with breast cancer, who do not carry a founder mutation, reported complete data on 602 female first-degree relatives of probands over age 20; 78 of these relatives had breast cancer. Segregation analysis was used to evaluate the likelihood of various genetic and nongenetic models. Sporadic, environmental, and general Mendelian genetic models fit the family data poorly and were rejected. A Mendelian recessive model fit better than dominant and codominant models, although none of these could be rejected. Cumulative incidence curves predicted by the recessive and codominant models fit observed incidence among first-degree relatives well. The assumption of Mendelian transmission of a major recessive gene(s) is compatible with the data. The recessive model predicts that 4% of women would carry the high-risk genotype, with 85% of them developing breast cancer by age 70. There was significant heterogeneity between these families and the 114 BRCA1/2 mutation-positive families from the same study population, implying that this apparent recessive effect is not because of undetected BRCA1/2 mutations. The study adds support for a major autosomal recessive component to breast cancer susceptibility.

Adult↗
PubMed1992

ABO segregation distortion in Visakhapatnam, India.

Distortions in mother-infant, mother-child and father-child segregation for the ABO system as well as in the sex of offspring are described in a sample from a maternity service and from families of Visakhapatnam, India. Some distortions follow the expected fetomaternal incompatibility depression, others the expected feto-maternal induction of tolerance, and some remain unexplained. A differential action of selective factors on male and female fetuses, infants and children was also found, but no hypothesis could be postulated to explain it. The mother-infant matrix was found to be different from the mother-child matrix probably due to the inclusion of the reproductive time only in the mother-infant matrix. Unexpectedly, father-child segregation distortions were also found.

ABO Blood-Group System↗
PubMedDate not supplied

The first international leprosy conference, Berlin, 1897: the politics of segregation.

The present paper examines the first attempts to internationalise the problem of leprosy, a subject hitherto overlooked by historians of imperialism and disease. The last decade of the nineteenth century saw many in the civilised countries of the imperialist West gripped by a paranoia about an invasion of leprosy via germ-laden immigrants and returning expatriates who had acquired the infection in leprosy endemic colonial possessions. Such alarmists clamoured for the adoption of vigorous leper segregation policies in such colonies. But the contagiousness of leprosy did not go unquestioned by other westerners. The convocation in Berlin of the first international meeting on leprosy revealed the interplay of differing and sometimes incompatible views about the containment of leprosy by segregation. The roles of officials from several countries, as well as the roles of five protagonists (Albert Ashmead, Jules Goldschmidt, Edvard Ehlers. Armauer Hansen, and Phineas Abraham) in the shaping of the Berlin Conference are here examined.

Congresses as Topic↗
PubMed1992

Segregation and linkage analysis.

Computer programs are available in the software package SAGE to perform a variety of segregation and linkage analyses used by human geneticists. These methods are designed specifically to uncover major gene segregation in pedigree data coming from non-inbred populations. With the aid of a closely linked polymorphic marker, they can detect a locus that contributes as little as 10% to the variation of a quantitative trait in a pedigree sample of several hundred individuals.

Animals↗
PubMed1992

Segregation analysis detects a major gene controlling blood infection levels in human malaria.

The profound influence that the genetic makeup of the host has on resistance to malaria infection has been established in numerous animal studies. This genetic heterogeneity is one of the main causes of the difficulties in developing an effective malaria vaccine. Segregation analysis is the first step in identifying the nature of genetic factors involved in the expression of human complex diseases, as infectious diseases. To assess the role of host genes in human malaria, we performed segregation analysis of blood parasite densities in 42 Cameroonian families by using both the unified mixed model and the class D regressive model of analysis. The results provide clear evidence for the presence of a recessive major gene controlling the degree of infection in human malaria. Parameter estimates show a frequency of .44-.48 for the deleterious allele, indicating that about 21% of the population is predisposed to high levels of infection.

Adolescent↗
PubMed1992

Rh segregation distortion: an artifact of ascertainment bias?

On the basis of Rh blood group data on mother-child pairs collected from the maternity clinic of a hospital in Chile, Valenzuela and Harb postulated that there is a significant segregation distortion at the Rh locus. For data collected from a hospital, biases of ascertainment cannot be ruled out. For the Rh blood group locus, there is a strong possibility of preferential admission of Rh(-) pregnant women, especially of those Rh(-) women with Rh(+) husbands. We show that the evidence of segregation distortion vanishes when the possibility of such preferential admissions are taken into account.

Adult↗
PubMed1991

Complex segregation analysis of primary hepatocellular carcinoma in Chinese families: interaction of inherited susceptibility and hepatitis B viral infection.

Primary hepatocellular carcinoma (PHC) is extremely common in eastern China, where it is both associated with chronic infection with hepatitis B virus (HBV) and often familial. Complex segregation analysis of 490 extended families was undertaken with liability classes defined by age, sex, and HBV infection status. The maximum-likelihood model suggests that a recessive allele with population frequency approximately .25 yields lifetime risk of PHC, in the presence of both HBV infection and genetic susceptibility, of .84 for males and .46 for females. The model further predicts that, in the absence of genetic susceptibility, lifetime risk of PHC is .09 for HBV-infected males and .01 for HBV-infected females and that, regardless of genotype, it is virtually zero for uninfected persons. Complex segregation analysis therefore provides evidence for the interaction of genotype, environmental exposure, sex and age in determining the occurrence of PHC in this population.

Carcinoma, Hepatocellular↗
PubMed1991

Segregation of callosal and association pathways during development in the visual cortex of the primate.

The segregation of callosal and association pathways in the developing visual cortex of the monkey was studied using the retrograde tracers fast blue and diamidino yellow. Quantitative analysis of the laminar distribution of labeled callosal and association neurons made it possible to reveal the shifting pattern of connections that characterizes the development of these two pathways. In the adult, callosal neurons are restricted to supragranular layers, where they are concentrated at the bottom of layer 3. Association neurons are located both in infra- and supragranular layers. Supragranular layer association neurons are concentrated in layer 2, with limited spread into layer 3 so that there is little overlap with callosal neurons. In the immature brain, callosal neurons are characterized by a tangential distribution that is more widespread than in the adult, while their laminar distribution undergoes little developmental change. Association neurons show two types of changes in their laminar distribution: (1) in the early fetus, there is a large excess of association neurons in supragranular layers, the adult distribution being achieved some time after birth; and (2) during maturation there is a selective elimination of at least 50% of the projections originating from the lower part of layers 2/3. Hence, the adult radial segregation of association and callosal pathways is achieved in part by regressive phenomena. The developmental reduction of bihemispheric projections is largely independent of changes in the organization of association neurons. Quantitative analysis of the morphology and spatial location of neurons sending axon collaterals to both hemispheres suggests that they constitute a subset of callosal neurons and that their frequency is determined by factors that regulate directly this population. These results are discussed with respect to the specification of visual cortical pathways during ontogenesis.

Amidines↗
PubMed2006

Expected coalescence times and segregating sites in a model of glacial cycles.

The climatic fluctuations of the Quaternary have influenced the distribution of numerous plant and animal species. Several species suffer population reduction and fragmentation, becoming restricted to refugia during glacial periods and expanding again during interglacials. The reduction in population size may reduce the effective population size, mean coalescence time and genetic variation, whereas an increased subdivision may have the opposite effect. To investigate these two opposing forces, we proposed a model in which a panmictic and a structured phase alternate, corresponding to interglacial and glacial periods. From this model, we derived an expression for the expected coalescence time and number of segregating sites for a pair of genes. We observed that increasing the number of demes or the duration of the structured phases causes an increase in coalescence time and expected levels of genetic variation. We compared numerical results with the ones expected for a panmictic population of constant size, and showed that the mean number of segregating sites can be greater in our model even when population size is much smaller in the structured phases. This points to the importance of population structure in the history of species subject to climatic fluctuations, and helps explain the long gene genealogies observed in several organisms.

Animals↗
PubMed1991

Complex segregation analysis of autism.

A complex segregation analysis of autism in 185 Utah families was carried out using the mixed model. The 209 affected individuals in these families represent nearly complete ascertainment of the autistic cases born in Utah between 1965 and 1984. The sibling recurrence risk for autism was 4.5% (95% confidence limits 2.8%-6.2%). Likelihoods were maximized for major-gene models, a polygenic model, a sibling-effect model, and a mixed model consisting of major-gene and shared-sibling effects. The analysis provided no evidence for major-locus inheritance of autism. Subdivision of the sample according to the probands' IQ levels showed that sibling recurrence risk did not vary consistently with IQ level. A segregation analysis of families in which the proband had an IQ less than 50 also failed to provide evidence for a major locus. However, because of the etiologic heterogeneity of this disorder, genetic analysis of other meaningful subsets of families could prove informative.

Autistic Disorder↗
PubMed1990

Segregation of mitochondrial genomes in a heteroplasmic lineage with Leber hereditary optic neuroretinopathy.

Relatively little is known about the factors maintaining mitochondrial DNA (mtDNA) sequence diversity in humans. A detailed understanding of the transmission genetics of mtDNA has been partly hampered by the lack of evidence for heteroplasmic individuals. Among families with Leber hereditary optic neuroretinopathy, we found a maternal lineage with individuals heteroplasmic for a single nucleotide change, and we were able to follow the segregation of polymorphic mitochondrial genomes over 3 generations. The results show that rapid segregation can occur but also that the level of heteroplasmy can be maintained from one generation to another. In this family the disease phenotype is associated with the mtDNA sequence change, confirming the involvement of the mutation in the disease.

Base Sequence↗