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Once linkage disequilibrium has been calculated for a dataset, a visualization method is often chosen to display the linkage disequilibrium to make it more easily understandable. The most common method is to use a heatmap, where colors are used to indicate the loci with positive linkage disequilibrium, and linkage equilibrium. This example ...
Association mapping has been most widely applied to the study of human disease, specifically in the form of a genome-wide association study (GWAS). A genome-wide association study is performed by scanning an entire genome for SNPs associated with a particular trait of interest, or in the case of human disease, with a particular disease of interest.
The approach involves using regression analysis to examine the relationship between linkage disequilibrium scores and the test statistics of the single-nucleotide polymorphisms (SNPs) from the GWAS. Here, the "linkage disequilibrium score" for a SNP "is the sum of LD r 2 measured with all other SNPs".
Linkage disequilibrium (LD) calculation; Identity by descent (IBD) and identity by state (IBS) matrix calculation; population stratification, such as a Principal component analysis; association analysis such as genome-wide association study for both basic case/control studies and quantitative traits; tests for epistasis
Hence, GWAS is a non-candidate-driven approach, in contrast to gene-specific candidate-driven studies. GWA studies identify SNPs and other variants in DNA associated with a disease, but they cannot on their own specify which genes are causal. [1] [2] [3] The first successful GWAS published in 2002 studied myocardial infarction. [4]
The most commonly used approach, block-based method, exploits the principle of linkage disequilibrium observed within haplotype blocks. [12] Several algorithms have been devised to partition chromosomal regions into haplotype blocks which are based on haplotype diversity , LD , four-gamete test and information complexity and tag SNPs are ...
Arlequin is a free population genetics software distributed as an integrated GUI data analysis software. [1] It performs several types of tests and calculations, including Fixation index (F st, also known as the "F-statistics" [2]), computing genetic distance, Hardy–Weinberg equilibrium, linkage disequilibrium, analysis of molecular variance, mismatch distribution, and pairwise difference tests.
Given loci and , the Linkage Disequilibrium between these loci, is denoted as D i j = p i j − p i p j {\displaystyle D_{ij}=p_{ij}-p_{i}p_{j}} where p i j {\displaystyle p_{ij}} is the frequency of the alternative allele at i and j co-occurring and p i {\displaystyle p_{i}} and p j {\displaystyle p_{j}} the frequency of the alternative allele ...