Genotype and environment

Basic concepts

• Gene: a segment of a polynucleotide chain that encodes the primary structure of a peptide as a translation product or is transcribed into the primary structure of RNA molecules that are not translated.
• Allele: a specific form of a gene, determined by a specific sequence of nucleotides and responsible for a specific form (quality or degree) of the traits encoded by it; different genes exist in the gene pools of populations in different and sometimes significant numbers of alleles; the information carried by most genes manifests itself in more than one trait of the organism = pleiotropic gene effect.
• Genotype: set of all alleles of an organism; the genotype collectively determines the extent or degree of the organism's phenotypic possibilities.
• Phenotype: the set of all the characteristics of an individual.

Genotype-environment relationship

• Environmental factors can either regulate or repress some parts of an organism's genetic program (through its regulatory systems); however, they can also modify it – affect the resulting form of the trait.
• Certain pathological forms of some traits of the organism arise mainly on the basis of the action of external factors, the genotype affects them only to a small extent.
• In general, the phenotype is influenced by the genotype and the influence of the environment.
• The degree to which a given trait is determined heritably in its form is expressed quantitatively as its heredity (heritability).

Monogenically determined traits (i.e. qualitative traits) are much less influenced by the environment, on the contrary, environmental factors have the greatest influence on polygenically inherited traits (i.e. quantitative)

• with quantitative traits, we are often interested in what are the relative shares of the hereditary component and environmental factors on the dispersion (variation) of the trait's phenotypic values, we then refer to the relative share of genetic factors on the total variance of the trait as heritability

 H² = V_G/V_P

   V_G – phenotype variance caused by genetic factors

   V_P – total variance of the phenotype value

H² can theoretically take on values ​​from 0 to 1, if it is equal to 0, the variance of the phenotype is fully dependent on environmental factors, with H²=1, on the contrary, environmental factors have no influence and all observed variance depends on genetic factors

 For more information see Heritability.

• Environmental factors generally have the greatest influence on the manifestation of polygenic, i.e. quantitative, traits – they are very plastic and their variability in different individuals therefore has two sources: external (environmental factors) and internal (constitution of the relevant polygenic system in the genotype).

 For more information see Multifactorial inheritance.

• Monogenically determined traits, i.e. qualitative traits, are much less influenced by the environment.

Links

Related Articles

• Alleles
• Genes
• Genotype
• Phenotype
• Multifactorial inheritance
• Traits

References

• ŠTEFÁNEK, Jiří. Medicína, nemoci, studium na 1. LF UK [online]. [cit. 11.02.2010]. <https://www.stefajir.cz/>.