In summary, a quantitative trait representing the maximum (over several years) number of cigarettes per day in the Framingham Heart Study's original and offspring cohorts was assessed in segregation and linkage analyses. Correlations between sibling pairs were consistent with the existence of a genetic component, as were variance components estimates of heritability (0.21–0.23); in addition, MCMC oligogenic segregation analysis estimated that 48% of the total phenotypic variance could be attributable to approximately two large QTLs.
