The phrase "an expression of existing" is not correct in standard written English.
It seems to be an incomplete thought and lacks clarity in meaning.
Example: "His artwork is an expression of existing in a chaotic world."
Alternatives: "a reflection of existence" or "a manifestation of being."
Therefore, it is more likely that hibernation results from the differential expression of existing genes that have widely and long existed among mammals [ 8, 12].
Mammalian hibernation is thought to be based on similar physiological mechanisms [41], [42] and a consequence of alternative regulation of general physiological programmes by the differential expression of existing genes.
Several pioneering studies showed that ectopic expression of existing proteins or their elements can restore functions destroyed by mutations or normalize the signaling pushed out of balance by disease and/or current small molecule based therapy.
That is, they provide not just an example of co-option but of gene sharing, such that only comparatively minor changes such as in the amount and location of gene expression of existing proteins was required to produce the first simple layers of tissue capable of refracting light (Piatigorsky 2007, 2008).
This is unfortunate, as NRSE-delimited UAS lines would have been useful to restrict the expression of existing Gal4-VP16 lines.
Instead, it appears that the symbiosis is maintained by altering expression of existing genes involved in vital cellular processes.
On the contrary, it appears that the maintenance of the symbiosis is modulated by the alteration of expression of existing genes involved in vital cellular processes.
Therefore, crop geneticists who increase the expression of existing genes (e.g., for drought tolerance) are presumably recreating options already rejected by natural selection.
By repressing the expression of existing genetic variation and of novel mutations, canalization reduces the responsiveness of traits to natural selection [ 5], and hence their potential to evolve [ 1, 3].
It has been hypothesized that eusocial behavior evolved from solitary behavior via changes in expression of existing "toolkits" of genes [ 1], in which ancient molecular and physiological pathways became modified and expressed in new contexts, thereby leading to profound behavioral and physiological changes.
