t(7;22)(q31;q12) in a uterine leiomyoma.
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Chromosome Fragility↗
Biomedical subjects
L Iselius
Publications and source records attributed to L Iselius.
Pronounced differences between native Chinese and Swedish populations in the polymorphic hydroxylations of debrisoquin and S-mephenytoin.
The frequency of poor metabolizers of debrisoquin was low and similar in four different native Chinese nationalities. In a total sample of 695 Chinese subjects, only seven (1.01%) had a urinary ratio between debrisoquin and 4-hydroxydebrisoquin greater than 12.6, which is the antimode between poor metabolizers and extensive metabolizers in white populations. This is significantly lower than the 6.82% found in 1011 white Swedish healthy subjects (p less than 0.0001). Admixture analysis indicated the occurrence of two distributions within extensive metabolizers among both Chinese and white subjects. The mean of the distribution of metabolic ratios among Chinese extensive metabolizers was shifted toward higher values compared with Swedish extensive metabolizers (p less than 0.01). The frequency of poor metabolizers of S-mephenytoin was higher in 137 Chinese (14.6%) than in 488 Swedish (3.3%) subjects (p less than 0.0001). Our findings imply that drugs metabolized by these two polymorphic hydroxylases should be prescribed in different dosages to Chinese and white subjects.
China↗
Transmission of breast cancer--a controversy resolved.
The Danish breast cancer data collected by Jacobsen (1946) have been reanalysed using morbid risks which incorporate mortality due to breast cancer. A dominant gene is favoured for familial breast cancer, supporting the conclusions of Williams & Anderson (1984) and later authors. Neglect of specific mortality does not greatly alter estimates of gene frequency and displacement, but the evidence for a major gene is inflated. No evidence for heterogeneity was found. Earlier claims of non-Mendelian transmission are in error since we have discovered that transmission probabilities are not correctly implemented in the computer program POINTER. Cases with bilateral breast cancer and males with breast cancer all belonged to families favouring a major gene. Of the cancer sites frequently reported to be associated with familial breast cancer, only ovarian cancer is significant in this material.
Breast Neoplasms↗
DNA haplotype analysis suggests linkage disequilibrium in the human insulin receptor gene.
Haplotypes of the insulin receptor gene were resolved in parents from Scandinavian nuclear families by studying the segregation of seven restriction fragment length polymorphisms (RFLPs). Of 97 unrelated parents, 41 had non-insulin-dependent diabetes mellitus (NIDDM). Considerable linkage disequilibrium in the region of the insulin receptor gene was found. Pairwise non-random associations were found between proximate RFLP sites, indicating the absence of recombinational hot spots between these sites. Thus, association studies between DNA polymorphisms at this locus and disease susceptibility genes could well be feasible in this population. Differences in the distribution of insulin receptor haplotypes were examined between NIDDM patients and healthy subjects. However, the differences observed were not statistically significant.
Adult↗
An unusual chromosome aberration 47,XX,+21,dup(12)(q13----q24),dup(12)(q13----q24) in a girl with Down syndrome and acute monocytic leukemia.
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Cells, Cultured↗
Genetic epidemiology of breast cancer in Britain.
A complex segregation analysis was conducted on two British series (one consecutive series of probands with breast cancer and one series ascertained through a normal consultand). Altogether there were 1248 nuclear families with breast cancer. A dominant gene with a frequency of 0.003 giving a lifetime penetrance of 0.83 is favoured. Ovarian, endometrial and cancers associated with the SBLA syndrome, as well as benign breast disease, were significantly more common in familial breast cancer than in families of single cases. Probands in families with more than one individual with breast cancer were non-significantly younger than isolated probands.
Adult↗
Von Hippel-Lindau disease: a genetic study.
Genetic aspects of von Hippel-Lindau (VHL) disease were studied in familial and isolated cases. Complex segregation analysis with pointers was performed in 38 kindreds with two or more affected members. Dominant inheritance with almost complete penetrance in the highest age classes (0.96 at 51 to 60 and 0.99 at 61 to 70 years) was confirmed and there was no evidence of heterogeneity between families ascertained through complete and incomplete selection. The point prevalence of heterozygotes in East Anglia was 1.89/100,000 (1/53,000) persons with an estimated birth incidence of 2.73/100,000 (1/36,000) live births. Reproductive fitness was 0.83. Direct and indirect estimates of the mutation rate were 4.4 (95% CI 0.9 to 7.9) x 10(-6)/gene/generation and 2.32 x 10(-6)/gene/generation respectively. There was no significant association between parental age or birth order and new mutations for VHL disease.
Adult↗
Transmission probabilities are not correctly implemented in the computer program POINTER.
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Ataxia↗
Leukaemia and transient leukaemia in Down syndrome.
We have reviewed 215 published cases of leukaemia and transient leukaemia in Down syndrome. There is an over-representation of mosaic trisomy 21, possibly the result, at least in part, of a survival effect. The most intriguing observation is a bimodal distribution of maternal age, produced largely because cases with true leukaemia have a significantly higher maternal age than cases with transient leukaemia (33.5 versus 29.5 years). In conjunction with evidence that meiosis I nondisjunction is infrequent in transient leukaemia, this suggests different mechanisms for the etiology of leukaemia and transient leukaemia, and favours a locus predisposing to transient leukaemia proximal to the centromere on the long arm of chromosome 21.
Adolescent↗
Hydroxylation polymorphisms of debrisoquine and mephenytoin in European populations.
European data on the polymorphic metabolism of debrisoquine, sparteine, dextromethorphan and mephenytoin have been collected. No significant difference in phenotype frequencies was found between the separate series for debrisoquine, sparteine and dextromethorphan, which supports the claim that these probe drugs reflect the same enzyme polymorphism. The mean frequency of the phenotype slow debrisoquine metaboliser was 7.65% based on 5005 determinations. The overall mean reflecting all three drugs and 8764 determinations was 7.40%. This is consistent with a gene frequency of 0.27 (95% confidence interval 0.26-0.28). The overall mean of the phenotype slow metaboliser of mephenytoin was 3.52% corresponding to a gene frequency of 0.19 (confidence interval 0.17-0.20). The incidence of slow metabolism of debrisoquine and possibly also of S-mephenytoin was homogeneous in the samples from European populations. This is of considerable interest as interethnic differences are now being found both in the phenotypic characters as well as the genotypes of polymorphic drug oxidation.
Debrisoquin↗
A linkage study of a large pedigree with X linked centronuclear myopathy.
Centronuclear myopathy (CNM) is a muscle wasting disorder that occurs in three distinct forms. Previous studies have shown linkage between the X linked form of the disease and the Xq28 probes ST14, DX13, and F8C. Our study on a previously unreported, three generation, X linked CNM family confirms linkage between these markers and the CNM locus (Z = 3.21, theta = 00). However, results from the laboratory of J-L Mandel (Samson and Hanover, personal communication) on a number of X linked CNM families exclude genetic linkage from the region Xq26-qter, suggesting genetic heterogeneity in this condition.
Cell Nucleus↗
Mapping of the gene for X-linked amelogenesis imperfecta by linkage analysis.
X-linked Amelogenesis imperfecta (AI) is a genetic disorder affecting the formation of enamel. In the present study two families, one with X-linked dominant and one with X-linked recessive AI, were studied by linkage analysis. Eleven cloned RFLP markers of known regional location were used. Evidence was obtained for linkage between the AI locus and the marker p782, defining the locus DXS85 at Xp22, by using two-point analysis. No recombination was scored between these two loci in 15 informative meioses, and a peak lod score (Zmax) of 4.45 was calculated at zero recombination fraction. Recombination was observed between the more distal locus DXS89 and AI, giving a peak lod score of 3.41 at a recombination fraction of .09. Recombination was also observed between the AI locus and the more proximal loci DXS43 and DXS41 (Zmax = 0.09 at theta max = 0.31 and Zmax = 0.61 at theta max = 0.28, respectively). Absence of linkage was observed between the AI locus and seven other loci, located proximal to DXS41 or on the long arm of the X chromosome. On the basis of two-point linkage analysis and analysis of crossover events, we propose the following order of loci at Xp22: DXS89-(AI, DXS85)-DXS43-DXS41-Xcen.
Amelogenesis Imperfecta↗
Complex segregation analysis for a three-allele locus: experience from an analysis of acid phosphatase activity.
A complex segregation analysis of acid phosphatase activity in 50 British families showed that the essential features of the acid phosphatase polymorphism, i.e., a major gene with three alleles, is retrieved by using the biallelic mixed model. The estimates of gene frequency and displacement obtained from segregation analysis were in agreement with those obtained from electrophoretic studies. In addition, there was evidence for a multifactorial component.
Acid Phosphatase↗
Translocation t(1;3) (p36;q21) in chronic myelomonocytic leukaemia.
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Animals↗
Sjögren-Larsson syndrome in Sweden: distribution of the gene.
The distribution of carriers of the gene for Sjögren-Larsson syndrome in Sweden suggests a center of dispersion in the county of Västerbotten in Northern Sweden. The origin of the spread of the gene can be traced back at least 700 years.
Gene Frequency↗
The distribution of the gene for the juvenile type of Gaucher disease in Sweden.
A study of 30 Swedish families with the Norrbottnian type of Gaucher disease provides evidence for two clusters of the gene, one close to Overkalix in the northern part of the county of Norrbotten and the other in the vicinity of Arvidsjaur in the southern part of the same county. The gene for Gaucher disease in Overkalix appeared later than that in Arvidsjaur. A founder moving from Arvidsjaur to Overkalix during the seventeenth century or two different mutations are the most likely explanations of this finding.
Female↗
Evidence for a major additive gene in ulcerative colitis.
Complex segregation analysis of 124 families with ulcerative colitis with two or more affected individuals suggests a rare additive major gene causing the disease with about 20% affected among the heterozygotes for the gene. There was no evidence for multifactorial inheritance.
Colitis, Ulcerative↗
A twin study of amino acid concentrations in cerebrospinal fluid.
The concentrations of amino acids in the cerebrospinal fluid (CSF) were measured in pairs of healthy mono- and dizygotic twins. Intraclass correlations were calculated. Genetic and cultural heritabilities were estimated using a path analytical model. CSF levels of glycine, tyrosine and arginine were shown to be influenced by genetic factors. Genetic variation was also shown for serine, alpha-aminobutyrate and leucine. The results were compared with results from a genetic analysis of the amino acids in serum.
Adolescent↗