Phenotypes

The phenotype is an observable or identifiable trait that is coded for by the genotype. This could be biochemical or physical. Phenotypes are not completely defined by the genotype other factors such as the environment can affect the observable traits. An example of this would be "Two people with a genetic risk of lung caner; if one smokes and the other does not, the smoker is much more likely to develop the disease" [Hartl et al, 2012 p63]. Examples of phenotypes could be, hair colour, eye colour, skin colour. Environmental factors can affect phenotypes, for example, skin colour can vary greatly with different levels of exposure to UV light from the sun causing darkening of the Melanin. Phenotype is also dependent on the type of allele that is expressed whether it is dominant, recessive. Also the phenotype can be a blend of phenotypes; incomplete dominance or both phenotypes expressed; co-dominant.