One such QTL, lsq4 on chromosome IV, appeared in three different inter-strain crosses as highly significant linkage-mapping peaks for longevity (each P < 10 −9 ) (Ebert et al., 1993 , 1996 ; Ayyadevara et al., 2001 , 2003 ; Shmookler Reis et al., 2007 ).
Considering only the biological N of 2 (two independent grow-ups of each strain, distinct from those initially screened in microarrays), and not the technical duplication of assays for each of those, 10 of the 18 genes assessed showed allele-dependent changes that were nominally significant ( P ≤ 0.05), whereas no more than one would be expected by chance (Table 3 ).