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F Demenais

Publications and source records attributed to F Demenais.

85 records · Page 5Linked to original sources
PubMed1984

An epidemiological and genetic study of facial clefting in France. II Segregation analysis.

Familial transmission of cleft lip with or without cleft palate (CL(P] and isolated cleft palate (CP) was studied in two French samples of 458 CL(P) and 156 CP nuclear families, using the recently implemented unified model. In neither case could discrimination be achieved between polygenic inheritance and monogenic inheritance with a high proportion of sporadic cases. In this type of disorder with a complex genetic basis the information furnished by such an approach, which only considers the affected status, is discussed. Future investigations on the joint familial transmission of the disease and different marker systems may help to identify the genes involved in these developmental anomalies.

Cleft Lip↗
PubMed1983

Exclusion of a tight linkage between familial polyposis coli and HLA.

Linkage was investigated between a dominant gene determining familial polyposis coli (FPC) and HLA in a large pedigree. A tight linkage was excluded at a value of the recombination fraction between 0 and 5%. Linkage studies with various markers should be pursued to permit detection of high risk individuals and to better understand the phenotypic variability observed in certain polyposis families.

Colonic Neoplasms↗
PubMed1983

Further analysis of familial transmission of congenital glaucoma.

A re-analysis of familial transmission of congenital glaucoma is performed here using the unified model and considering, respectively, joint and conditional likelihoods. Whereas the familial aggregation of this malformation is consistent with the segregation of a recessive major gene and a high proportion of sporadic cases using conditional likelihood, this is rejected using joint likelihood. The difference in the results obtained using each of these two strategies is discussed.

Female↗
PubMed1982

Neural tube defects in France: segregation analysis.

Segregation analysis was performed on a subset of a large body of French data comprising 298 nuclear families. Two models were used in this analysis: the transmission probability model [Elston and Stewart, 1971; Elston, 1981] and the mixed model [Morton and MacLean, 1974]. Both models are consistent with familial aggregation of neural tube defects, in this sample, being due to either the segregation of a recessive major gene or a sibling environmental effect, or both factors. In each case, other environmental factors are also involved. These results were compared to the findings of other studies and discussed in respect to the diversity of the epidemiological features displayed by different populations. Some observations of vertical transmission in a British study and the proportion of affected first cousins, in both France and Great Britain, lead us to reject a possible absence of transmission. We propose a monogenic component with a large influence of environmental factors, some of which may be common to sibs, to explain the occurrence of neural tube defects in this sample.

Environment↗
PubMed1982

A five-generation family with sacral agenesis and spina bifida: possible similarities with the mouse T-locus.

In man, a malformation that recalls some of the defects associated with T/t mutants in the mouse is sacral agenesis. We report on a family with a high incidence of sacral malformation, ranging from a complete absence of the sacrum (SA), with or without spina bifida aperta, to a spina bifida occulta (SBO) that could only be detected by x-ray. The condition appeared in a man with four children who were all affect, and thereafter, to varying degrees, in 17 of his 28 descendants. Segregation analysis has been performed in this family, using the Elston and Stewart transmission probability model [1971]. The two traits (SA and SBO) were first studied separated and then together. A fully penetrant major dominant gene is show to cause SA. When the phenotypes SA and SBO are considered together, Mendelian transmission is rejected. This could be explained genetically by two alternative hypotheses: genetic heterogeneity or a dominant major gene transmitted in excess by heterozygotes (tau Aa A = 0.896), suggesting a segregation distortion property of an allele at a T-like locus.

Adult↗
PubMed1981

Segregation analysis of congenital glaucoma: approach by two differential models.

To determine the mode of inheritance of congenital glaucoma, segregation analysis was performed using two different models: the transmission probability model and the mixed model. Whereas the latter, testing for monogenic inheritance in the presence of both monogenic and polygenic components, results in strong evidence for a major locus, the former, testing for Mendelian segregation at one locus, rejects this hypothesis. The differences in the results of these two models are discussed and are attributed to the underlying structure of each. Genetic heterogeneity of congenital glucoma is proposed.

Female↗
PubMed1980

[Epidemiologic and genetic studies of spina bifida (author's transl)].

The incidence of neural tube defects among the siblings of 311 index cases has been estimated at 1.9%. The recurrence risk is higher for a same type malformation i.e. spina bifida after the birth of a child with spina bifida. The same features appear in other surveys from the literature although the general recurrence risk is lower in our series. The sex ratio appears to be inversely correlated with the incidence of the malformation, being higher in France than in Britain. Interpretation of the segregation analysis of the data is difficult. Genetic counseling is based upon the empirical risk (1.25% in the studied cases). Indications of antenatal diagnosis are discussed.

Female↗
PubMed1980

Diseases having two classes of severity: estimation of the proportions of each manifestation by maximum likelihood.

In diseases having variable expressivity, the proportions of the different manifestations of the affection in the population may be different from the observed proportions in a sample when probabilities of ascertainment of these various manifestations are different from each other. This bias can be avoided by taking into account the respective probabilities of ascertainment of these manifestations and by estimating the proportions by maximum likelihood. In this paper, the method of estimation is developed for the particular case of two different phenotypes. Probabilities of observations are calculated, and scores and measures of information are derived. The different factors affecting the respective proportions of affected individuals are: the difference between probabilities of ascertainment of the two forms, the probability of ascertainment of the milder form, the proportion of the more severe form in the population, and the proportion of sibships with a single affected child in the population. The method is applied to published data on retinoblastoma. Validity of the assumptions is discussed and these assumptions are checked using the retinoblastoma data.

Eye Neoplasms↗
PubMed1979

[Incidence of cystic fibrosis in Brittany (author's transl)].

Incidence of cystic fibrosis has been estimated in three adjacent geographic areas of Brittany: North Finistere, South Finistere and Morbihan. This incidence is respectively 6.0 x 10(-4), 4.8 x 10(-4), 2.9 x 10(-4) in these three areas. A significant difference between North Finistere and Morbihan was found. Without proofs in favor of natural selection, genetic drift seems to be a possible explanation of this variation. Moreover, as in other studies, a genetic heterogeneity of the disease was not shown.

Cystic Fibrosis↗
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↗
PubMed1978

Cluster of cystic fibrosis cases in a limited area of Brittany (France).

Cystic fibrosis in the northern sector of the French "département" of Finistère is 1:1787 live births. Within this sector a concentration of the disease was found in a small area. The minimal frequency in this area, from 1946 to 1972, was calculated as 1 per 377 live births, the gene frequency being 0.0515. Genealogic analysis, going back to the beginning of the 18th century, showed a relationship between 8 of the 10 families to which the patients belonged. The origin of the deleterious genes may be explained by a least five primary ancestral couples living in the 18th century. Random drift is the most probable explanation for the concentration of cystic fibrosis in this region.

Cystic Fibrosis↗
PubMed1978

Consanguinity in multifactorial inheritance. Application to data on congenital glaucoma.

The increase of parental consanguinity in multifactorial inheritance is evaluated by calculating the expected incidence of affected children whose parents are first cousins, using several values, namely for condition frequency and heritability of liability. This increase is compared to the expected increase in recessive inheritance, when one or more loci are involved. The method is illustrated by examples of recessive and multifactorial conditions and applied, as a test of discrimination between different modes of inheritance, to data on congenital glaucoma.

Consanguinity↗