Genotype–phenotype distinction

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Similar genotypic changes may result in similar phenotypic alterations, even across a wide range of species.[1]

The genotype–phenotype distinction is drawn in

traits and their evolution
.

Overview

The terms "genotype" and "phenotype" were created by Wilhelm Johannsen in 1911,[2] although the meaning of the terms and the significance of the distinction have evolved since they were introduced.[3]

It is the organism's physical properties that directly determine its chances of survival and reproductive output, but the inheritance of physical properties is dependent on the inheritance of genes. Therefore, understanding the theory of evolution via natural selection requires understanding the genotype–phenotype distinction. The genes contribute to a trait, and the phenotype is the observable manifestation of the genes (and therefore the genotype that affects the trait). If a white mouse had recessive genes that caused the genes responsible for color to be inactive, its genotype would be responsible for its phenotype (the white color).[citation needed]

The mapping of a set of genotypes to a set of phenotypes is sometimes referred to as the genotype–phenotype map.[4]

Sub-Saharan
and European ancestry, yet have noticeably differing phenotypes.

An organism's genotype is a major (the largest by far for morphology) influencing factor in the development of its phenotype, but it is not the only one. Even two organisms with identical genotypes may differ in their phenotypes, due to phenotypic plasticity. To what extent a particular genotype influences a phenotype depends on the relative dominance, penetrance, and expresivity of the alleles in question.

One experiences this in everyday life with

monozygous (i.e. identical) twins. Identical twins share the same genotype, since their genomes are identical; but they never have the same phenotype, although their phenotypes may be very similar. This is apparent in the fact that close relations can always tell them apart, even though others might not be able to see the subtle differences. Further, identical twins can be distinguished by their fingerprints, which are never completely identical.[citation needed
]

Phenotypic plasticity

The concept of

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

Genetic canalization

In contrast to phenotypic plasticity, the concept of genetic canalization addresses the extent to which an organism's phenotype allows conclusions about its genotype. A phenotype is said to be canalized if mutations (changes in the genome) do not noticeably affect the physical properties of the organism. This means that a canalized phenotype may form from a large variety of different genotypes, in which case it is not possible to exactly predict the genotype from knowledge of the phenotype (i.e. the genotype–phenotype map is not invertible). If canalization is not present, small changes in the genome have an immediate effect on the phenotype that develops.

Importance to evolutionary biology

According to

Mendelian genetics can predict the next generation of genotypes, thus completing the cycle. Even if non-Mendelian aspects of molecular genetics
are ignored, this is a gargantuan task. Visualizing the transformation schematically:

(adapted from Lewontin 1974, p. 12). T1 represents the genetic and

epigenetic laws, the aspects of functional biology, or development, that transform a genotype into phenotype. This is the "genotype–phenotype map
". T2 is the transformation due to natural selection, T3 are epigenetic relations that predict genotypes based on the selected phenotypes and finally T4 the rules of Mendelian genetics.

In practice, there are two bodies of evolutionary theory that exist in parallel, traditional population genetics operating in the genotype space and the

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.

References

  1. PMID 19956802
    .
  2. PMID 24691957
    .
  3. ^ Taylor, Peter; Lewontin, Richard. "The Genotype-Phenotype Distinction". Retrieved 21 June 2017.
  4. PMID 20083632
    .
  5. ISBN 978-0231083188
    .

External links
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