Why this was the case remains unknown.
For example, it remains unknown if loss of one ATP2A2 allele elicits the compensatory upregulation of the second functional allele or whether SERCA2a haploinsufficiency in human heart leads to a greater, and apparently effective, reliance on transsarcolemmal Ca2+-flux.
For example, it remains unknown why in bees the chemical nature of queen-characteristic and fertility-linked compounds is much more diverse than in ants and wasps [ 12], how queen signals evolved across this group and how they might have been co-opted from fertility signals in solitary ancestors.
For example, although it remains unknown whether a "safe" threshold exists for prenatal and early-life exposure to methylmercury, evidence of methylmercury damage to neurodevelopment has been accumulating since the 1950s.
However, the nature of the horizontally acquired genes remains unknown: for example, did the products of HGT arise ancestrally in the analyzed taxa, becoming shuffled over time through recombination and high rates of decay, or are HGT products continually sculpting the variation within the accessory genome overtop of a highly reductive nature of all genes within the genome?
Whether the primary role of ZmTCRRs is exerted in the transmitting tissue remains unknown, although examples of non cell autonomous functions based on protein movement can be found in the literature [ 44- 46].
The function of most lincRNAs remains unknown, but the example of imprinted macro ncRNAs indicates that some may regulate nearby genes by long-range cis-silencing.
Sequestering of other shikimate-derived metabolites, for example, ubiquinones, menaquinones, iron chelating siderophores and vitamins remains unknown.
Examples (Subgroups) "[In introduction:] However, it remains unknown whether all these genetic and environmental factors act independently or jointly and to what extent they as a group can predict the occurrence of AMD or progression to advanced AMD from early and intermediate stages.
Although there are several well-characterized examples of these phenomena, their existence in humans remains unknown.
