In contrast, the temporal dimension of migration is typically more difficult to determine.
While it is difficult to determine whether these typically euchromatic regions have formed heterochromatin, these observations imply that unfavorable transcriptional states are targeted by Clr4 activity.
One of the major impediments is that QTL mapping typically produces large genetic intervals, which make it difficult to determine the best candidates for the causal genes.
As these factors typically do not exist in isolation, it remains difficult to determine to what degree each of these factors plays a role in colorectal adenoma and cancer risk.
Additionally, the physical treatment often consists of various interventions and is typically also combined with drugs and other treatments which make it difficult to determine the effects of a single intervention.
Additionally, tumor specimens (unless obtained via laser capture microdissection) are typically in fact a mixture of tumor cells and stromal cells, making it difficult to determine whether a gene of interest is being expressed by the tumor, stroma, or both.
Further, since any single couple may typically produce a few oocytes or embryos that are abnormal merely by chance, it is difficult to determine whether sibling embryos as a group, or an embryo cohort, is "normal".
Second, kinases are typically subject to complex post-translational and regulatory interactions in the cell that make it very difficult to determine a form of the enzyme that might serve as a faithful representative of its intracellular state.
Interplate earthquakes typically occur in offshore areas, far away from onshore seismic stations, and, hence, it tends to be difficult to determine their hypocenter locations, especially focal depths, with adequate precision.
Female crickets typically rely on phonotaxis for mate location and mate choice, but the function of male phonotaxis is usually difficult to determine [29].
