Correlations among other parameters were also reported emphasizing a balance among all actions that generate or remove cells within the same subpopulation. In particular, when we imposed cell proportions obtained considering Sca-1 + data, these relations were observed in PC1 and PC2 subpopulations. Otherwise, using data obtained from CD44 + /CD242 experiments, the trade-off was observed in CSCs. This behavior explains the coexistence of CSCs, PCs, and differentiated cells in the same tumor which, in turn, reflects the cancer heterogeneity that could result from the various differentiation grades of genetically identical cells.Active trachoma in Gambian children has also been associated with the IL-10 -3917-G allele.This idea has been borne out by the analysis of mice bearing germline deletion of individual ERM proteins, where abnormalities are largely restricted to tissues expressing only one family member. The variation of mutation effects with fitness, together with the fact that error rates can be easily modified as a consequence of mutations producing genotypes with variable capacity to cause errors, suggest that mutation rates are a character subjected to the action of natural selection. Stable environments would favour low mutation rates, constrained only by the costs of error-repair mechanisms. In contrast to this, environments subjected to frequent changes would select for increased mutation rates that permit faster adaptation to the new conditions. However, the optimization of the mutation rate is not only determined by its impact on adaptation but also by the consequences that the variation of this character has on fitness. High mutation rates can increase the number of deleterious mutations, whereas low mutation rates can have metabolic costs associated. The existence of these opposing forces causes that natural selection often fails to fully optimize this character. The study of the evolution of mutation rates has been addressed theoretically, and using digital organisms. There are also many reported examples of natural and experimental bacterial populations with higher than standard mutation rates.