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PubMed1987

[Segregation analysis of familial polyposis coli].

The results of Mendelian analysis of the hereditary colon polyposis are presented, considering age influence on manifestation of the character and specificity of the data obtained. The possibility of pleiotropic monogenic control of the hereditary polyposis and primary colon cancer is checked up and confirmed.

Adenomatous Polyposis Coli↗
PubMed1988

[The genetics of breast cancer, population and familial research and segregation analysis].

The data on clinico-genealogy studies of 1046 probands with breast cancer and their relatives are presented. The nature of inheritance corresponded to the Mendelian model. As to other families, there is no strong evidence for the monogene model both with complete and incomplete penetrance of mutant homo- and heterozygotes. Penetrance of homozygotes was 7.9-30.5%, this being 2.0-7.3% for heterozygotes. The conclusion is drawn that it is necessary to consider the regularities of inheritance of breast cancer in the light of the multifactorial model.

Adult↗
PubMed1978

Efficiency and robustness of pedigree segregation analysis.

Different pedigree structures and likelihoods are examined to determine their efficiency for parameter estimation under one-locus models. For the cases simulated, family size has little effect; estimates based on unconditional likelihoods are generally more efficient than those based on conditional likelihoods. The proposed method of pedigree analysis under a one-locus model is found to be robust in the analysis of nuclear families: skewness of the data and polygenic inheritance will not lead to the spurious detection of major loci unless they occur simultaneously, and together with a moderate amount of environmental correlation among sibs.

Gene Frequency↗
PubMed1985

The segregation-linkage analysis of genetically determined characters.

The model of combined segregation-linkage analysis is presented. The method offers the opportunity of simultaneous estimation of recombination fraction between the locus of genetic marker and that of a disease gene and the evaluation of its inheritance pattern. The computer programme MUBAS estimates combinations of parameters: dominance-d, penetrance-t and recombination fraction by the method of maximum likelihood using the distribution of the observed numbers of sib pairs: ill/proband and healthy/proband.

Genetic Linkage↗
PubMed1977

Extrachromosomal inheritance in Schizosaccharomyces pombe. III. Isolation and characterization of paromomycin-resistant mutants.

In the antimycin--resistant mutant anar-8 of the fission yeast Schizosaccharomyces pombe (Sch.p.) spontaneous mutants were isolated showing high resistance to the aminoglycoside antibiotic paromomycin. All mutants were resistant to the structurally related antibiotic neomycin. Tetrad analysis, mitotic segregation analysis, and mitotic haploidization revealed extrachromosomal, very likely mitochondrial inheritance. In contrast to the rapid segregation of mitochondrial markers in zygotic clones of Saccharomyces cerevisiae (S.c.) the heteroplasmic state of diploids proved to persist for at least 50 generations after zygote formation. Stationary cultures of the paromomycin-resistant mutants parr-106 and parr-112 contain up to 6% respiratory-deficient mutants, but no reversion to paromomycin-sensitivity was observed among 1700-1800 colonies tested. The ability of mutant anar-8 to produce spontaneously respiratory-deficient mutants could be separated from the antimycin-resistant phenotype of anar-8.

Ascomycota↗
PubMed1988

Family resemblance for serum uric acid in a Jerusalem sample of families.

Familial aggregation of serum uric acid was studied in a sample of families examined in the Jerusalem Lipid Research Clinic. We first examined homogeneity of familial correlations across the major origin groups in the Israeli population sample. In general correlations were homogeneous across origin groups, except for spouse pairs. Pooled correlations among biological relatives across the origin groups were all statistically significant. Spouse correlation upon adjustment for concomitant variables was moderately positive (r = 0.115), yet significantly different from zero. Genetic and cultural determinants of uric acid were estimated utilizing a path model with 10 parameters to be estimated from a total of 16 correlations. Under a reduced model, genetic heritability (h2) was estimated to be 0.47 +/- 0.05 and cultural heritability (c2) was 0.11 +/- 0.03. However, our data gave suggestive evidence that cultural heritability was higher in parents (c2 = 0.28) than in children (c2 = 0.10). Commingling analysis and segregation analysis were also performed, and our findings imply that in the Israeli population there is no evidence for a major gene for high uric acid levels segregating in families.

Adult↗
PubMed1990

Evidence for a major gene in familial anencephaly.

A 21-year-old white woman sought counseling after the birth of two consecutive anencephalic male fetuses with complete rachischisis and discordant renal dysplasia. The presence of parental consanguinity prompted reconsideration of recessive inheritance. The segregation ratio from 23 additional consanguineous cases was compared with that observed in 294 presumably nonconsanguineous families previously reported. Using classical segregation analysis, the segregation ratios in the non-sporadic cases were consistent with a major autosomal recessive locus in both populations.

Abortion, Spontaneous↗
PubMed1989

Familial analysis of bipolar affective disorder using logistic models.

Data on bipolar affective disorder in 187 pedigrees from the Collaborative Depression Study were analyzed using logistic models that have been extended to incorporate age of onset information. Logistic regression analysis and segregation analysis revealed evidence for complex familial effects on this disorder.

Age Factors↗
PubMed1990

Transmission of a psychometric indicator for liability to schizophrenia in normal families.

The genetic analysis of schizophrenia would be facilitated by identification of a heritable correlate of liability. Deviance on an index of Minnesota Multiphasic Personality Inventory (MMPI) signs is associated with the disease phenotype; the familial aggregation and mode of transmission of this continuous psychometric indicator have yet to be established. In this paper, we examine the indicator through commingling analysis and segregation analysis with both the mixed and unified models on 65 nuclear families containing 211 normal individuals. Evidence for a high degree of familiality is found. Analysis of untransformed data under a conditional likelihood provides evidence for Mendelian transmission of a major gene with commingling of two distributions. The frequency of the "high index score" allele is 0.15, with the gene accounting for 31% of the total population variance; such a locus would be relevant to the study of psychopathology as 28% of the population would carry at least one deviant allele. When power-transformed scores are used to eliminate skewness, there is evidence for one distribution and it is not possible to distinguish single gene from multifactorial (polygenic or cultural) inheritance. While our findings regarding mode of transmission must be interpreted cautiously and confirmation of a single locus requires further study, demonstration of familiality warrants continued investigation of the index as an indicator of liability for schizophrenia.

Adolescent↗
PubMed1979

Congenital glaucoma: genetic models.

Modes of inheritance of congenital glaucoma have been studied. Two methods of analysis, complex segregation analysis and frequency of congenital glaucoma in second- and third-degree relatives, did not permit one to retain a unitary mode of inheritance ofthis malformation. Genetic heterogeneity of congenital glaucoma is proposed. Recurrence risks and guidelines for genetic counseling in specified situations are given.

Adult↗
PubMed1992

Molecular cloning of a gene (cfp) encoding the cytoplasmic filament protein P59Nc and its genetic relationship to the snowflake locus of Neurospora crassa.

P59Nc is a 59-kD polypeptide associated with 8-10-nm diameter cellular filaments in normal Neurospora crassa strains. Abnormally sized and shaped bundles of these structures are present in N. crassa strains carrying mutations at the locus sn (snowflake). By using molecular cloning and restriction fragment length polymorphism (RFLP) segregation analysis strategies we show here that sn is not the genetic locus of P59Nc. Several P59Nc cDNAs were cloned from a N. crassa lambda GT11 library after immunoscreening with specific polyclonal anti-P59Nc antibodies. Additional longer cDNAs were obtained from a N. crassa cDNA-lambda ZAP library. When used as probes in Southern blots of total DNA from wild-type strains, multicent-2 (a multiple mutant strain), and snowflake mutants, the P59Nc cDNAs revealed comparable patterns of hybridizing bands for all of the restriction enzymes tested. Analysis of segregation of BclI and ClaI RFLPs, detected in the genomic region of the P59Nc gene (locus cfp: cellular filament polypeptide), among a set of strains designed for RFLP mapping, or among selected progeny of crosses involving a snowflake parent, respectively, indicate that (i) there is in N. crassa a single cfp locus positioned on the right arm of linkage group VII between the locus for and the proximal breakpoint of the translocation T(VII----I)5936; (ii) the sn mutations in the centromere region of chromosome I do not represent translocations of cfp; and (iii) the snowflake mutants possesses a normal copy of the P59Nc gene on their chromosomes VII.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1987

Centromeric proteins recognized by CREST sera and meiotic chromosome segregation.

Analysis of the peptides recognized by CREST sera was carried out in different mouse tissues and cells, including spermatozoa. In all cases, a polypeptide of Mr = 18,000 was recognized by the sera and occasionally two other proteins of Mr = 80,000 and Mr = 140,000 were observed after immunoblotting of nuclear proteins. In both early and late spermatids, centromeric staining was observed after incubation and immunofluorescence with CREST sera. After detergent treatment, it was even possible to detect centromeric staining in mature spermatozoa. In spermatid cells, the immunofluorescent pattern presented a binomial distribution of the number of fluorescent spots, with a mean value around half of the haploid number of chromosomes. Since this pattern is the result of chromosome segregation after meiosis II, our data suggest that this centromeric peptide is not directly implicated in the chromosome segregation process. On the other hand, the distribution of spots after immunofluorescence suggests a different organization of centromeric components in meiosis I and meiosis II.

Animals↗
PubMed1989

Equivalence of the mixed and regressive models for genetic analysis. I. Continuous traits.

The mixed model of segregation analysis specifies major gene effects and partitions the residual variance into polygenic and environmental components. The model explains familial correlations essentially in terms of genetic causation. The regressive model, on the other hand, is constructed by successively conditioning on ancestral phenotypes and major genes. Familial patterns of dependence are described in terms of correlations without necessarily introducing a particular scheme of causal relationship. These two approaches are compared both theoretically and numerically through computer simulations for the case of continuous traits on nuclear families. The class D regressive model, which is characterized by equal sib-sib correlations, is mathematically and numerically equivalent to the mixed model. The simpler class A regressive model, which is also characterized by equal sib-sib correlations determined in this case by the common parentage, provides good estimates of the mixed model parameters: major gene parameters and residual polygenic heritability, derived from the parent-offspring correlation. However, in the absence of a major gene, the restriction imposed by the class A model on the sibling correlation can affect the conclusions of segregation analysis: False inference of a major gene was observed in two out of ten replicates. Our simulations also indicate that the mixed model allowing for different heritabilities in adults and children leads to correct estimates of the major gene parameters and residual familial correlations (parent-offspring and sib-sib) as specified by the class A model. For all the models studied, major gene effects, when present, are correctly detected and estimated.

Adult↗