Fig. 1.

Re-replication greatly stimulates gene amplification. (A) Induction of re-replication from ARS317. Strains containing an ade3-2p copy number reporter cassette integrated at Chr IV_567kb were arrested in G₂/M phase and treated with galactose to trigger re-initiation of ARS317. aCGH analysis of re-replication (>2C) is shown for Chr IV. All other chromosomes maintained a 2C copy number. Top: YJL6974, a non–re-replicating strain with ARS317 in cassette. Middle: YJL6555, a re-replicating strain with no ARS317 in cassette. Bottom: YJL6558, a re-replicating strain with ARS317 in cassette. (B) ARS317 re-replication stimulates gene amplification. Left: Frequency of one-half to one-eighth red-sectored colonies (mean ± SEM, n = 2 to 7 induction replicates; table S1) after 0 or 3 hours of galactose induction of YJL6974, YJL6555, and YJL6558. Right: Amplification frequency estimated by multiplying sector frequency by the fraction of sectored colonies displaying reporter cassette amplification (tables S2 and S4). (C) Red sectors induced by re-replication display gene amplifications. Thirty-five red sectors derived from YJL6558 were analyzed by aCGH and classified on the basis of the copy number profile of Chr IV. A schematic of Chr IV (top) shows the positions of Ty elements (triangles), the centromere (circle), and the ade3-2p cassette (black bar).