These alleles encode slightly different versions of a protein, which cause different phenotypical traits. CYP2D6 shows the largest phenotypical variability among the CYPs, largely due to genetic polymorphism. In a monotypic species, all populations exhibit the same genetic and phenotypical characteristics. Genetic variation accounts for 40% of phenotypical variation. Uniparental inheritance of imprinted genes can also result in phenotypical anomalies. The definition of structural variation does not imply anything about frequency or phenotypical effects. Viral infections may have clinically relevant phenotypical CPEs. Most occurrences of UPD result in no phenotypical anomalies. It bears close genotypical and phenotypical resemblance to "Bacillus cereus" and "Bacillus thuringiensis". Nevertheless, a molecule mechanism that mediates their phenotypical change has not been identified yet. Most of the phenotypical variation among breeds can be explained by the sex-linked gene "K". By the 17th century the term began to refer to physical (phenotypical) traits. Phenotypical variation can include both visual and behavioral aspects. Iris texture is a phenotypical feature that develops during gestation and remains unchanged after birth.