Fig. 1.

Stress-induced repeat instability as a potential source of novel phenotypic variation. Under normal environmental conditions, repeat allele lengths are distributed narrowly in a population (dark gray bars), but when severe stress diverts Hsp90 from its normal role in maintaining genome stability, the distribution of repeat lengths broadens (light gray bars). Similarly, an unstressed population expresses a narrow range of phenotypes (solid line), which expands when stress is applied (dashed line). The ability of microsatellite repeats to incrementally influence gene expression suggests that stress-induced repeat instability may underlie some fraction of the increased range of phenotypes observed in response to stress