Figure 1.

Mutagen sensitivity test. (A) On day 0, adults for a cross that generates mutant flies and sibling controls (usually heterozygous) are put into vials. (B) On day 3, the adults are transferred to new vials. The first set of vials is kept as a mock treated [(C) day 4, after eggs have hatched and larvae are feeding] or untreated control; the second set (brood two) is the treatment group. (D) On day 6, adults are removed from the brood two vials. (E) Second-brood vials are treated on day 7. (F, G) Adult progeny are counted, typically for 5–7 days after eclosion begins. The ratio of mutant to nonmutant is determined in each control vial (R_C), and each corresponding treated vial (R_T). Relative survival is expressed as R_T/R_C, with each vial being a separate biological replicate. The total number of flies in each treated vial, divided by the total number in the corresponding control vial, gives a measure of overall survival after treatment (there may be a difference in number of progeny between broods, even without treatment; some vials could be left untreated to determine the effects of brood-to-brood variation).