Biomedical subjects

A Rebaï

Publications and source records attributed to A Rebaï.

6 recordsLinked to original sources

PubMed2005

Data for 10 autosomal STR markers in South Tunisian population.

Allele frequencies, together with some parameters of forensic interest for 10 STRs (D3S1358, vWA, D16S539, D2S1338, D8S1179, D21S11, D18S51, D19S433, TH01 and FGA) were estimated from 201 unrelated individuals originating from southern Tunisia. Significant deviation from Hardy-Weinberg equilibrium was observed for only one marker. Comparative analyses between our population data and other populations showed that only markers D3S158, vWA and FGA were homogenous among populations. The combination of these 10 STR loci provide a powerful tool for forensic identification in Tunisian population.

DNA Fingerprinting↗

PubMed2005

[Linkage disequilibrium in the human genome and its exploitation].

This present review gives an overview on Linkage disequilibrium (LD), its measures and its different utilizations in human genetics studies. In the first part, we provide a detailed and a simplified presentation focusing on the definition of LD, its measures and the major software for its evaluation. Thereafter, we describe and discuss the biological and evolutionary mechanisms which create, remodel, maintain or destroy LD in human population. Consensus has now emerged on the pattern of LD in the genome which has a block-like organization with block of high disequilibrium interrupted by recombination hotspots. However, no standard method exists for the determination of such blocks and, more importantly, for the identification of TagSNP. This would yield inconsistencies between different studies of the same genes, compromising the practical use of TagSNP in association studies. The ACE gene is used to illustrate this. Will it be possible to identify consensus TagSNP that could be used consistently in all populations for testing association of candidate genes in common diseases? What is the part of myth and reality in what is called "individualized medicine"? We conclude that further LD studies are needed to get clear insights into this matter.

Case-Control Studies↗

PubMed2000

More about quantitative trait locus mapping with diallel designs.

We present a general regression-based method for mapping quantitative trait loci (QTL) by combining different populations derived from diallel designs. The model expresses, at any map position, the phenotypic value of each individual as a function of the specific-mean of the population to which the individual belongs, the additive and dominance effects of the alleles carried by the parents of that population and the probabilities of QTL genotypes conditional on those of neighbouring markers. Standard linear model procedures (ordinary or iteratively reweighted least-squares) are used for estimation and test of the parameters.

Alleles↗

PubMed2000

[Linkage analysis for complex diseases: a new life for an old method].

In this paper, I present the main approaches used in gene mapping of complex human diseases by linkage analysis based on molecular markers. The first section describes the traditional LOD-score analysis and gives a review of different improvements and refinements of this approach, which has been proposed in order to take into account complicating factors such as incomplete penetrance, genetic heterogeneity and unknown mode of inheritance. The second section describes the three main approaches of non-parametric linkage analysis, for which there is no need to specify a genetic model (mode of inheritance, allele frequencies, ..). A comparison between these three methods, which may seem to be more appropriate for complex diseases, is given based on the most recent published studies. In the third section and discussion, I compare the LOD-score and non-parametric methods by stressing the advantages and drawbacks of each approach as found in recent publications. I deduce that, in spite of its apparent and assumed inappropriateness to the analysis of complex diseases, the LOD-score method is still very useful and could provide, in some circumstances, more power and precision than model-free methods.

Chromosome Mapping↗

PubMed1994

Approximate thresholds of interval mapping tests for QTL detection.

A general method is proposed for calculating approximate thresholds of interval mapping tests for quantitative trait loci (QTL) detection. Simulation results show that this method, when applied to backcross and F2 populations, gives good approximations and is useful for any situation. Programs which calculate these thresholds for backcross, recombinant inbreds and F2 for any given level and any chromosome with any given distribution of codominant markers were written in Fortran 77 and are available under request. The approach presented here could be used to obtain, after suitable calculations, thresholds for most segregating populations used in QTL mapping experiments.

Biometry↗

PubMed1994

Constructing confidence intervals for QTL location.

We describe a method for constructing the confidence interval of the QTL location parameter. This method is developed in the local asymptotic framework, leading to a linear model at each position of the putative QTL. The idea is to construct a likelihood ratio test, using statistics whose asymptotic distribution does not depend on the nuisance parameters and in particular on the effect of the QTL. We show theoretical properties of the confidence interval built with this test, and compare it with the classical confidence interval using simulations. We show in particular, that our confidence interval has the correct probability of containing the true map location of the QTL, for almost all QTLs, whereas the classical confidence interval can be very biased for QTLs having small effect.

Chromosome Mapping↗