Association mapping localizes genetic influences on a phenotype by testing population genetic association with markers. Linkage disequilibrium allows a typed marker to tag a nearby causal variant; historical genetic recombination can narrow the associated interval. Population stratification can produce association without a local causal relation.
// Target: biology.bigb
An observed genetic marker tags an unobserved causal genetic variant when linkage disequilibrium correlates their allele indicators. Their squared allelic correlation measures prediction strength. Under standard local-alternative score-test approximations, using the marker rather than the causal allele reduces the noncentrality parameter by roughly , suggesting a sample-size multiplier about . This is an approximation requiring the same disease model and sampling design, not a universal power identity.
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Association mapping, also known as linkage disequilibrium mapping, is a genetic analysis method used to identify the relationship between genetic markers and traits of interest in a population. It is particularly useful in understanding the genetic basis of complex traits, such as those influenced by multiple genes and environmental factors. ### Key Concepts: 1. **Genetic Markers**: These are specific sequences in the genome, such as single nucleotide polymorphisms (SNPs), that vary among individuals.