摘要:

SummaryRoutine Q‐banding chromosome analysis detected the jumping behaviour of bright fluorescent chromosome 22 satellites (22s+) in two unrelated males (case 1 ascertained for recurrent abortions and case 2 for infertility), and in the mother of one of them, all with a normal karyotype. The 22s + was present in more than 90% of the cells. In a minority of the cells the polymorphism was present alternatively on another acrocentric, on one chromosome 22 and on another acrocentric, on both chromosomes 22 or it was absent. We take these findings as evidence of mitotic exchanges between the short arms of the acrocentric chromosomes. The presence of a stable 22s + in the fibroblasts of case 1 and in the lymphocytes of his son indicates that acrocentric short arm exchanges depend both on the type of tissue and on the genetic content of all the other acrocentric

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01180.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryThe genealogies of 533 individuals with an intracranial aneurysm (IA) born in the Saguenay‐Lac‐Saint‐Jean region, a geographically isolated area located in northeastern Quebec, were reconstructed using a population‐based register. A control group consisting of three individuals of the same sex and born on the same day and in the same municipality than the IA patients was created; the genealogies of the 1599 controls were also reconstructed. The coefficients of inbreeding and kinship were calculated. Familial aggregation, i.e. the presence of IA in two or more first‐ to third‐degree relatives, was also sought. The mean inbreeding coefficient was lower in the IA group than in the control group (7·92 × 10−4versus 10·04 × 10−4). The mean kinship coefficient was higher in the IA group than in the control group (2·17 × 10−4versus 1·55 × 10−4). Forty‐eight IA patients (9·0%) were first‐degree relatives compared to only 1·9% of the control individuals. The proportion of individuals showing familial aggregation was higher in the IA group than in the control group (29·8% and 18·6% respectively). These results strongly suggest that some IA are geneti

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01181.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryA new method for analysis of multifactorial traits is described which involves mathematical definition of MZ and DZ twin concordances in terms of penetrance and the number of contributory genes. This allows the number of major genes and their joint penetrance to be estimated. Application to familial schizophrenia indicates causation by a single dominant allele, a deduction supported by several treatments of observed risks in other family members. Lifetime empiric risks are analysed in the context of four conditions: genetic predisposition, prenatal trauma, psychological or other trauma in early adult life and possible exacerbation of symptoms associated with close contact with affected family members. Comparative empiric risks for twins and sibs are explained by consideration of coincident gestations, season of birth and the sharing of a chorionic sac and foetal blood supply. The data are consistent with penetrance being complete in homozygotes and generally around 0·33 in heterozygotes, but it increases in additive fashion depending on risk factors associated with the type of relationship with one or more affected family members and factors associated with twinning. The influence of an affected parent is nearly 3 times as great as that of an affected sibling. The population frequency of heterozygotes is deduced to be around 2·6

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01182.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Summary(1) The microgeographic structure of Sardinia, well documented from a historical and linguistic point of view, further supported by archaeological evidence, can also be dissected at the genetic level: gene frequencies show heterogeneities which are statistically significant.(2) Dendrogram analyses performed with different methods lead to the same result: even if gene frequencies cluster linguistically defined geographic domains in agreement with historical and archaeological evidence, no phylogenetic tree can be inferred, very likely because the assumptions which allow a phylogenetic tree to be a valid model of evolution (mainly constant evolutionary rates and independence between branches) do not apply to the genetic history of Sardinia.(3) Evidence of a qualitative association between distribution of genes and distribution of languages or dialects seems to emerge also at the microgeographic level of our analysis. More linguistic and genetic data are planned to be considered.

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01183.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummarySimulation studies are used to explore the properties of procedures for estimating components of variance and constructing test statistics in genetic linkage studies of quantitative traits. We evaluated the bias and median squared error of estimates of the linked additive genetic variance obtained by regression, maximum likelihood and quasilikelihood estimation procedures. The quasilikelihood and regression procedures provided unbiased estimates of the additive component of variance. Maximum likelihood procedures that assumed multivariate normality were biased for most sample sizes considered but had more precision for most generating models than regression or quasilikelihood methods did. Wald tests derived from quasilikelihood procedures had similar or greater power than Wald tests based upon estimators from maximum likelihood analyses. Quasilikelihood estimation may therefore be preferable whenever there is uncertainty about the generating distribution for the error variance, but the robustness of this approach is offset by its required computational complexity.

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01184.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryThe admixture model for linkage heterogeneity is modified to take account of the difference in recombination fractions in the two sexes. The data used may concern a single (marker) locus on one chromosome, which is suspected of being sometimes near a (disease) locus for a particular condition of interest, or there may be data on more than one locus on this chromosome. There may be data on a locus or loci on a second chromosome, which is also suspected of sometimes carrying an allele for the condition in question. The general principle for the analysis is the same in all such cases, though details may differ. The object is to estimate the relevant recombination fractions, and the proportions of cases in which the allele for the condition falls on each chromosome.

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01185.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryThe use of IBD proportions from a large set of affected sib‐pair data to estimate some or all of the main parameters describing the inheritance of a disease susceptibility gene is here considered. We assume there is no recombination present and neglect ascertainment bias, and assume that there are four distinct parental haplotypes present in each famil

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01186.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryWe report a new polymorphism in the complement C7 gene that results from an A‐C transversion in intron 12, 27 bp upstream of exon 13 (C712.‐27) and 36 bp upstream of the point mutation that underlies the C7 M/N antigenic polymorphism. The C7 12.‐27 polymorphism subdivides C7 M haplotypes, but not C7 N. It also sheds light on the evolution of the various types of deficiency genes at the adjacent C6

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01187.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01188.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0003-4800    

DOI:10.1111/j.1469-1809.1996.tb01189.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY