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M de Andrade

Publications and source records attributed to M de Andrade.

46 records · Page 3Linked to original sources
PubMed1995

Estimation of quantitative genetic parameters under non-normal models.

In traditional quantitative genetics, the relationship between the observed value of a quantitative trait in a set of families and its genetic and environmental contributions can be described as a linear additive relationship. Generally, it is assumed that the genetic and environmental effects are independent and normally distributed. Consequently, the quantitative trait also has a normal distribution. However, there are some situations where the phenotype does not follow the normal distribution. To deal with this problem the author suggests the families of distributions that belong to the Johnson Translation System (JTS). As an example, two dependent quantitative traits, weight and height, are investigated assuming that they have a lognormal and normal distribution, respectively. Computational methods for estimating the genotypic variances and covariances are presented.

Finland↗
PubMed1995

Relationship of the apolipoprotein E polymorphism with carotid artery atherosclerosis.

From the cohort taking part in the Atherosclerosis Risk in Communities (ARIC) study, a multicenter investigation of atherosclerosis and its sequelae in women and men ages 45-64 years, a sample of 145 subjects with significant carotid artery atherosclerosis but without clinically recognized coronary heart disease was identified along with 224 group-matched control subjects. The aim of this paper is to measure the association of the apolipoprotein (apo) E polymorphism with the prevalence of significant carotid artery atherosclerotic disease (CAAD) after considering the contribution of established risk factor variables. The first model used a stepwise selection procedure to define a group of significant physical and lifestyle characteristics and a group of significant plasma lipid, lipoprotein, and apolipoprotein variables that were predictive of CAAD status in this sample. Those variables selected included age (years), body mass index (BMI; kg/m2), consumption of cigarettes (CigYears; number of cigarettes/d x the number of smoking years), hypertension status, high-density lipoprotein (HDL)-cholesterol (mg/dl), total cholesterol (mg/dl), and Lp[a] (micrograms/ml). The second model was built by forcing into the equation an a priori set of demographic, anthropometric, and lipoprotein variables, which were age, BMI, CigYears, hypertensive status, LDL-cholesterol, and HDL-cholesterol. In both models, the apo E genotype epsilon 2/3 was related to CAAD status. For both models, the estimated odds ratio of being a CAAD case associated with the apo E genotype epsilon 2/3 was > 2:1. The mechanism of the observed association between the epsilon 2/3 genotype and carotid atherosclerosis is unknown, but it is likely due to the known effects of the E2 isoform in causing delayed clearance of triglyceride-rich lipoproteins.

Adult↗
PubMed1994

Allelic associations of two polymorphic microsatellites in intron 40 of the human von Willebrand factor gene.

At intron 40 of the von Willebrand factor (vWF) gene, two GATA-repeat polymorphic sites exist that are physically separated by 212 bp. At the first site (vWF1 locus), seven segregating repeat alleles were observed in a Brazilian Caucasian population, and at the second (vWF2 locus) there were eight alleles, detected through PCR amplifications of this DNA region. Haplotype analysis of individuals revealed 36 different haplotypes in a sample of 338 chromosomes examined. Allele frequencies between generations and gender at each locus were not significantly different, and the genotype frequencies were consistent with their Hardy-Weinberg expectations. Linkage disequilibrium between loci is highly significant with positive allele size association; that is, large alleles at the loci tend to occur together, and so do the small alleles. Variability at each locus appeared to have arisen in a stepwise fashion, suggesting replication slippage as a possible mechanism of production of new alleles. However, we observed an increased number of haplotypes, in contrast with the predictions of a stepwise production of variation in the entire region, suggesting some form of "cooperative" changes between loci that could be due to either gene conversion, or a common control mechanism of production of new variation at these repeat polymorphism sites. The high degree of polymorphism (gene diversity values of 72% and 78% at vWF1 and vWF2, respectively, and of 93% at the haplotype level) makes these markers informative for paternity testing, genetic counseling, and individual-identification purposes.

Adult↗
PubMed1994

Linkage disequilibria among (CA)n polymorphisms in the human dystrophin gene and their implications in carrier detection and prenatal diagnosis in Duchenne and Becker muscular dystrophies.

Four short tandem repeat loci, characterized by length polymorphisms of (CA)n repeats, have been detected within introns 44, 45, 49, and 50 of the human dystrophin gene. The predicted heterozygosities for these loci range from 72 to 93%, and observed allele numbers range from 6 to 19 in 57 normal chromosomes, revealing their high degree of polymorphism. Evidence for significant disequilibria between the loci within introns 49 and 50 is found. These data appear to be consistent with observations of recombination frequencies between these markers and the length of the intron 44 in relation to the entire region. In addition, these four loci are collectively found to be 100% informative in carrier detection/prenatal diagnosis of Becker and Duchenne muscular dystrophies (B/DMD), whereas scoring the (CA)n markers within introns 45 and 49 alone gives a 99.6% success rate.

Alleles↗
PubMed1993

Intraclass and interclass correlations of allele sizes within and between loci in DNA typing data.

Nonparametric measures of correlations of DNA fragment lengths within and between variable number of tandem repeat (VNTR) loci are proposed to test the hypothesis of random association of allele sizes at VNTR loci. Transformations of these nonparametric correlation measures are suggested to detect deviations of their null expectations caused by population subdivision and errors of measurement of VNTR fragment lengths. Analytic and permutation-based computer simulation studies are performed to show that under the hypothesis of independence of allele sizes the transformed correlation measures are normally distributed, irrespective of the VNTR fragment size distribution in the population even when the number of individuals samples is as low as 100. Power calculations are performed to establish that the current population data on six VNTR loci in the US Hispanic sample are in accordance with the hypothesis of random association of allele sizes within and between loci. Implications of these results in the context of forensic use of DNA typing are also discussed.

Alleles↗
PubMed1991

Carrier detection and prenatal diagnosis in Duchenne and Becker muscular dystrophy families, using dinucleotide repeat polymorphisms.

To improve carrier detection and prenatal diagnosis for Duchenne and Becker muscular dystrophy families, we determined allele frequencies and measures of variation for four (dC-dA)n.(dG-dT)n loci identified within a deletion-prone region of the human dystrophin gene. The loci are highly polymorphic, with predicted heterozygosities of 71.6%-93.3%. Direct DNA sequence analysis of the (dC-dA)n.(dG-dT)n locus in intron 49 revealed an additional length polymorphism which varies by single-basepair increments, is adjacent to the dinucleotide repeat block, and enhances the polymorphic content of this marker. The four (dC-dA)n.(dG-dT)n loci are each easily amplified by PCR in two diplex reactions. The variability of allele lengths at these loci makes them ideal for carrier detection and prenatal diagnosis, often providing diagnostic information when RFLP analysis is uninformative. These markers have aided in identification of deletion mutations, exclusion of maternal cell contamination of chorionic villus samples, confirmation of paternity, and mapping of gene recombinations. The allele identification of these loci can be performed either with a radiolabel or with an automated, nonradioactive, fluorescent gel detection system.

Alleles↗
PubMedDate not supplied

Complex segregation analysis of facial clefting in Chile.

Nonsyndromic cleft lip with or without cleft palate (CL/P) has an incidence of 1.5 per 1,000 live births in Chile, with 1.7 per 1,000 in males and 1.3 per 1,000 in females, which is nearly the same as the level found in Asian populations. The high rate of occurrence of CL/P in Chile is probably due to the presence of Amerindian genes in Chilean populations. Using the computer program PAP, a complex segregation analysis of CL/P was conducted for 67 multigeneration pedigrees from Chile, each ascertained from one affected proband. These pedigrees yielded 162 affected individuals and over 898 family members who were included in the analysis. The most parsimonious model of transmission indicated the presence of an autosomal dominant gene with reduced (20-25%) penetrance.

Chile↗