Comparison of the power and accuracy of biallelic and microsatellite markers in population-based gene-mapping methods

Article Abstract:

Power and accuracy of microsatellite and biallelic markers have been compared for use in population-based gene-mapping. Single-nucleotide polymorphisms (SNPs) are available and are good for fully automated genotyping and they offer simple insertion/deletion as well. These things make them good for marking in positional cloning. Selection of markers for mapping of human disease genes must depend ultimately on power to detect linkage between marker and locus and accuracy of estimation of map location. A mathematical framework and analytical formulas have been developed for calculation of power and accuracy. The impact of various factors involved, for biallelic SNPs and microsatellites, has been studied using two population-based gene-mapping methods, likelihood-based linkage-disequilibrium mapping and transmission/disequilibrium test. Guidance in selection of markers and design of the sample scheme for positional cloning is included.

United States, Evaluation, Economic aspects, Mathematical models, Genetic research

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Williams syndrome: use of chromosomal microdeletions as a tool to dissect cognitive and physical phenotypes

Article Abstract:

In Williams syndrome (WS) certain physical, behavioral and cognitive abnormalities are caused by an approximately 1.5-Mb deletion on one copy of chromosome 7. Psychometric and genetic testing has been done with patients with small deletions in the WS critical region. It seems neither LIMK1 nor STX1A hemizygosity likely contributes to any part of the WS phenotype. Such patients are important in looking at subtle and very penetrant phenotypes. Studying the molecular mechanism of the phenotype may help in identification of genes important for human behavior and cognition. ELN (ital) encodes elastin and is deleted in WS, and patients with only ELN (ital) mutations had hemizygosity for elastin responsible for the cardiology problems seen in WS. LIMK1, which (ital) encodes a protein tyrosine kinase expressed in the brain during development, is missing, as are some others.

Genetic aspects, Cognition, Clinical neuropsychology, Williams syndrome

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Significance levels in complex inheritance

Article Abstract:

Significance levels in complex inheritance have been explored and a method combining multipoint linkage and allelic association developed for testing for a regional candidate locus. A LOD score of three or greater is necessary but not sufficient to signify that a linkage test has been reliable, both for complex inheritance and for major loci. Various factors affect the threshold. Marker density is not a major factor. Biases in evaluation of LOD scores are of the greatest importance. That is true especially when allowance for estimation of nuisance parameters in multiple models has been inadequate. Allelic association is the only practical means of locating polygenes.

Models, Usage, Genetics

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