Genotype–phenotype distinction

To what extent a particular genotype influences a phenotype depends on the relative dominance, penetrance, and expresivity of the alleles in question.

A high level of plasticity means that environmental factors have a strong influence on the particular phenotype that develops.

If there is little plasticity, the phenotype of an organism can be reliably predicted from knowledge of the genotype, regardless of environmental peculiarities during development.

An example of high plasticity can be observed in larval newts1: when these larvae sense the presence of predators such as dragonflies, they develop larger heads and tails relative to their body size and display darker pigmentation.

Larvae with these traits have a higher chance of survival when exposed to the predators, but grow more slowly than other phenotypes.

A phenotype is said to be canalized if mutations (changes in the genome) do not noticeably affect the physical properties of the organism.

T1 represents the genetic and epigenetic laws, the aspects of functional biology, or development, that transform a genotype into phenotype.

For example, if the phenotype is almost one-to-one with genotype (sickle-cell disease) or the time-scale is sufficiently short, the "constants" can be treated as such; however, there are also many situations where that assumption does not hold.