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Wyświetlanie 1-2 z 2
Tytuł:
The em Algorithm and Its Implementation for the Estimation of Frequencies of snp-Haplotypes
Autorzy:
Polańska, J.
Powiązania:
https://bibliotekanauki.pl/articles/908153.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
genetyka
informatyka
algorithms
haplotypes
likelihood functions
gene frequency
Opis:
A haplotype analysis is becoming increasingly important in studying complex genetic diseases. Various algorithms and specialized computer software have been developed to statistically estimate haplotype frequencies from marker phenotypes in unrelated individuals. However, currently there are very few empirical reports on the performance of the methods for the recovery of haplotype frequencies. One of the most widely used methods of haplotype reconstruction is the Maximum Likelihood method, employing the Expectation-Maximization (EM) algorithm. The aim of this study is to explore the variability of the EM estimates of the haplotype frequency for real data. We analyzed haplotypes at the BLM, WRN, RECQL and ATM genes with 8-14 biallelic markers per gene in 300 individuals. We also re-analyzed the data presented by Mano et al. (2002). We studied the convergence speed, the shape of the loglikelihood hypersurface, and the existence of local maxima, as well as their relations with heterozygosity, the linkage disequilibrium and departures from the Hardy-Weinberg equilibrium. Our study contributes to determining practical values for algorithm sensitivities.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2003, 13, 3; 419-429
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sampling Properties of Estimators of Nucleotide Diversity at Discovered snp Sites
Autorzy:
Renwick, A.
Bonnen, P. E.
Trikka, D.
Nelson, D. L.
Chakraborty, R.
Kimmel, M.
Powiązania:
https://bibliotekanauki.pl/articles/908150.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
genetyka
statystyka
single nucleotide polymorphisms
ascertainment bias
nucleotide diversity
molecular evolution
Opis:
SNP sites are generally discovered by sequencing regions of the human genome in a limited number of individuals. This may leave SNP sites present in the region, but containing rare mutant nucleotides, undetected. Consequently, estimates of nucleotide diversity obtained from assays of detected SNP sites are biased. In this research we present a statistical model of the SNP discovery process, which is used to evaluate the extent of this bias. This model involves the symmetric Beta distribution of variant frequencies at SNP sites, with an additional probability that there is no SNP at any given site. Under this model of allele frequency distributions at SNP sites, we show that nucleotide diversity is always underestimated. However, the extent of bias does not seem to exceed 10-15% for the analyzed data. We find that our model of allele frequency distributions at SNP sites is consistent with SNP statistics derived based on new SNP data at ATM, BLM, RQL and WRN gene regions. The application of the theory to these new SNP data as well as to the literature data at the LPL gene region indicates that in spite of ascertainment biases, the observed differences of nucleotide diversity across these gene regions are real. This provides interesting evidence concerning the heterogeneity of the rates of nucleotide substitution across the genome.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2003, 13, 3; 385-394
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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