Hsp90 suppression can cause novel morphologies in Drosophila and Arabidopsis, yet research so far has mainly looked at the qualitative traits which are affected. Recently some research was done to see how it can effect the smaller quantitative traits which are more important or more effective for evolution. It was found that Hsp90 only affected some very specific quantitative traits which tended to be invariable and very discrete.
The fact that the traits shown when Hsp90 expression is reduced depends on the genetic background of the flies is evidence that the traits evolve separately and are then released when Hsp90 stops its buffering effect. Bristle number and scutellor mutations are threshold traits like the qualitative mutations buffered by Hsp90. It was found that a wide range of responses are buffered more strongly whilst a narrower range of mutations can more easily break down the Hsp90 buffer and become independent or 'fixed' into the population.
While Hsp90 can cause an increase in heritability and evolvability of a genotype in a population, the effects for an individual cannot be controlled, so use of Hsp90 suppression as a tool for evolution would likely be a last hope grasp for evolution, as many of the individuals in the population would die from the mutations that occur, or become significantly less fit.
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