= Solution
<Genetic linkage> analysis asks whether a <genetic marker> and a disease <genetic locus> cosegregate within families more often than would be expected under <independent assortment>. It uses <pedigrees> and <Mendelian segregation> to estimate the <recombination fraction> $\theta$, with evidence for linkage arising when the data favor $\theta<1/2$. Even when founders are in linkage equilibrium, linked loci can show familial cosegregation.
<Genetic association> analysis instead asks whether observed <allele> or <genotype> frequencies differ with disease status in a sampled population, often comparing cases with controls. It can detect a causal variant or a correlated <genetic marker> through <linkage disequilibrium>; population structure and selection can also create association. \b[Linkage is about familial transmission; association is about population dependence.] Neither an association alone nor a low family recombination estimate establishes that the marker itself causes disease.
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