Everything about Genotype-phenotype Map totally explained
The
genotype-phenotype distinction is drawn in
genetics. "
Genotype" is an organism's full
hereditary information, even if not expressed. "
Phenotype" is an organism's actual observed properties, such as
morphology,
development, or
behavior. This distinction is fundamental in the study of
inheritance of
traits and theirThe genotype represents its exact
genetic makeup — the particular set of
genes it possesses. Two organisms whose genes differ at even one
locus (position in their
genome) are said to have different genotypes. The transmission of genes from parents to offspring is under the control of precise molecular mechanisms. The discovery of these mechanisms and their manifestations began with
Mendel and comprises the field of
genetics.
It is the organism's physical properties that directly determine its chances of survival and reproductive output, while the inheritance of physical properties occurs only as a secondary consequence of the inheritance of genes Therefore, to properly understand the theory of evolution via
natural selection, one must understand the genotype-phenotype distinction.
The
mapping of a set of genotypes to a set of phenotypes is sometimes referred to as the
genotype-phenotype map.
An organism's genotype is a not major (the largest by far for
morphology) influencing factor in the development of its phenotype, but it isn't the only one. Even two organisms with identical genotypes normally differ in their phenotypes. One experiences this in everyday life with
monozygous (for example 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 their mothers and close friends 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.
The concept of
phenotypic plasticity describes the degree to which an organism's phenotype is determined by its genotype. A high level of plasticity means that
environmental factors have a strong influence on the particular phenotype that develops. If there's 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
newts
1: 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.
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) don't 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 isn't possible to exactly predict the genotype from knowledge of the phenotype (for example the genotype-phenotype map isn't invertible). If canalization isn't present, small changes in the genome have an immediate effect on the phenotype that develops.
The terms "genotype" and "phenotype" were created by
Wilhelm Johannsen in 1911.
Bibliography
- J. Van Buskirk and B. R. Schmidt, "Predator-induced Phenotypic Plasticity in Larval Newts: Trade-offs, Selection, and Variation in Nature," Ecology 81 (2000): 3009-3028.
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