Organism physical, biochemical, and physiologic traits {phenotype}| result from genotype and environment interactions. Johannsen invented the word [1909]. Organisms can express behavior and structure genes. Some phenotypes confer better fitness and adaptation. Offspring phenotypes are typically intermediate between parent phenotypes.
roles
Phenotypes can have adaptations, be pleiotropes, have neutral fitness, or have exaptations.
Gene phenotypes vary in expression {expressivity}.
New species come from repeated-body-segment structure and number changes. Modifications are similar to existing parts {homeosis} {homeotic transformation}. Parts can have jumps. For example, upper thoracic vertebrae can have no ribs, or lower cervical vertebrae can have ribs.
Gene phenotypes have expression ranges {penetrance}.
Traits {phenocopy} can have appearance similar to other traits but have different causes. Phenocopy rate increases as onset age increases and as severity decreases.
Genotypes and environments vary phenotypes {phenotypic variance}.
One gene can control more than one phenotype {pleiotropism}|.
Organism functions and behaviors {trait}| have genetic determinants. Tasting phenylthiocarbamide and other traits can depend on only one gene.
Structures can arise and then later have purposes {exaptation, role}.
Phenotypes can be adaptation side effects {spandrel, phenotype}, because they are pleiotropic.
Genetic traits typically interact {gene interaction}, allowing different optimum conditions or gene combinations. Environments and other-gene effects can suppress gene potentials. Most genes act differently depending on other-gene actions. Gene changes can affect individuals, families, troops, groups, demes, populations, and species. Genes that favor adaptability at more than one level are reinforcing. Genes that favor one level but harm another level are counteracting.
Most traits {polygenetic trait}, such as intelligence and personality, depend on multiple genes. Learning and environment affect polygenetic phenotypes more.
Independent genes can add {polygenic inheritance} effects to make phenotypes, such as skin color and height.
Independent genes can interact to produce phenotypes. Independent dominant genes {complementary genes} can interact to determine phenotype.
Independent genes can interact so one dominant allele is complementary but other dominant allele is not complementary {supplementary genes}, such as in albinism or skin color.
Earlier traits can reappear in modern organisms {atavism}|.
Animals {chimera}| can have parts or genes from other animals.
In individuals, different phenotypes can express at different body locations {mosaicism}| {mosaic, genetics}. Individuals can have male or female tissues, where one allele prevails.
Lower-organism phenotypes can appear in individuals {recidivism}|.
individual regularity {idiographic law}.
species regularity {nomothetic law}.
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Date Modified: 2022.0225