Espistasi – Wikipedia Wikipedia

In genetics, the epistasi It is a form of interaction between genes, in which a genetic mutation depends on the presence or absence of mutations in one or more other genes, called “modifiers”. The effect of the mutation is therefore dependent on the genetic background in which it manifests itself. ^[first] Epistatic mutations produce different effects when they overlap.

Originally the term epistasi It indicated that the effect of a variant gene was masked by the presence of a different gene. ^[2] The concept of “epistasis” was introduced in 1907 in the field of genetics by William Bateson and by his collaborators Florence Durham and Muriel Wherele Onslow, ^[3] But it is currently also used in biochemistry, computational, bioinformatics and evolutionary biology.

The effects of the genes are currently quantified by evaluating the breadth of the phenotype (height, pigmentation, growth rate) or by evaluating the protein activity by biochemical (protein bonds or enzymatic catalysis). Computational or evolutionary biology models aim to describe the effects of the epistasis on a genomic scale and the consequences on evolution. ^{[4] [5] [6]}

The identification of episthetic couples is considerably demanding both from a computational and statistical point of view; For this reason, some studies give priority to epistatic couples. ^{[7] [8]}

The phenomenon occurs when a pair of alleles covers the phenotypic expression of another pair of alleles. The phenotypic characteristics of the individual will therefore be given by the result of this interaction; The gene that masks the expression of another gene is defined epistatico , the gene whose expression is masked is defined hypostatic ^[9] .
For example if the Y gene is episthetic on the X gene; Gene X is called hyposotic compared to the Y.

More precisely, in the Dominant Epistasis , the presence of an epistatic allele A It has the effect of preventing the transition from phenotype 1 to phenotype 2, a passage that is also controlled by another Allelic couple, whose alleles can be B O b ; It is said then that A is episthetic on B and B because, due to the presence of a copy of A , from phenotype 1 it is not clear if the second gene has at least one dominant allele or both recessive alleles.

In the’ recessive epistasis , the absence of an allele A , that is, the presence of a Epistatic Alleral Couple a / a , has the effect of preventing (therefore the allele A it would assist him) the transition from phenotype 1 to phenotype 2, a passage that is also controlled by another Allelic couple, whose alleles can be B O b ; It is said then that A/A is epistatic on B and B Because, due to the presence of an Allelical couple a / a , cannot be obtained from phenotype 1 if the second gene has at least one dominant allele or both recessive alleles.
These two types of epistasis, of course, can be combined with each other more or less complex, giving rise to phenotypic relationships of the progeny of a different intersection depending on the number of genes in epi-static relationship considered and depending on the relationships of Epistase between each of the two allean couples.

An example of recessive epistasis It is Albinism, in which the presence of a recessive allein pair (A/A), which alters the production of melanin, covers any other pair of not strictly dominant alleles (therefore b/b or b/b) that goes to influence the color of the skin, eyes or hair.

Another example of recessive epistasis is in the coloring of the hair of Labrador breed dogs, in which a gene (commonly called “and”) surplus on the expression of the B gene (dominant, which gives black color, unlike the “B gene “That gives brown in color), thus determining the light color of the cloak.

Bombay’s phenotype, at the level of the type or further example of recessive epistasis, in which defects of the FUT1 and FUT2 genes can ‘hide’ the phenotypic expression of any alleles determining antigens A, b. ^[ten]

An example of Dominant Epistasis It is given by the gray color of the cloak of the horse (Boco). When the gray gene is present in the dominant state, it means that other colors are not manifested (phenotypic ratio at F2 12: 3: 1).