However, some species are exceptional in that they lay few eggs but exhibit apterous males, which we hypothesize could be due to other selective pressures selecting against the re-appearance of winged morphs.
Thus, selection either maintains existing alleles over long periods of time (balancing selection) or maintains diversity by selecting against fixation of existing alleles (diversifying selection).
The application of selection index methodology in selecting against hip dysplasia using the trait scores was explored and potential improvements in accuracy (directly related to response to selection) of over 10% are reported compared to the current total hip score.
Purifying selection acts to prevent divergence of structure and function by selecting against extreme values of a trait, in contrast to directional selection, where a single phenotype is selected and therefore allele frequency shifts in one direction.
Due to the complex genetics of the cannabis plant, growers selectively breeding THC-rich plants were also selecting against the gene that produces CBD.
However, it is also possible that fisheries in wild stocks are imposing considerably stronger selection than what is assumed in models, by selecting against behavioural traits.
In males, selection through nonretention mortality also had a stabilizing effect, selecting against fish in the shortest and longest length categories and further eroding the bimodal nature of the preharvest run.
While we found that harvest mortality selected against the largest fish, selection due to nonretention mortality was directional with the opposite effect, predominantly selecting against smaller fish.
The feed rate was kept low in order to ensure yeast extract and hence leucine starvation, thereby selecting against the plasmid-free cells.
The unique I-SceI site in the counterselection cassette is cut by I-SceI endonuclease, strongly selecting against nonrecombinant clones and yielding up to 30% correct recombinants.
Thus, culture adaptation could be selecting against the ability of stem cells to differentiate.
