Allelic genes - an explanation of the concept, ways of interaction
The genotype includes a large numbera variety of genes, which in turn act as a single whole. The founder of genetics, Mendel, in his writings described that he discovered only one possibility of interaction of allelic genes - when there is an absolute dominance (predominance) of one of the alleles, while the second remains completely recessive (passive, ie, does not participate in interaction). But once we say that the phenotypic manifestation of genes (external, noticeable look) can not depend only on one or a pair of genes, because it is the result of the interaction of the whole system.
In reality, proteins and enzymes interact, not genes.
In the fundamentals of genetics there are only 2 typesthe interaction of genes - the first is the interaction of allelic genes, the second, respectively, non-allelic. It is only necessary to understand the material side of this issue, because not any concepts from the textbook interact, but proteins that are synthesized according to a certain program in the cytoplasm of cells, and the number of these proteins is estimated at millions. The program itself, on which proteins will be synthesized, and as a result, their further interaction will develop, is laid down in the genes that are supplied by external commands, being in the chromosomes of cells (ultrascopic cell organelles).
What genes are called alleles?
Allelic genes are genes that occupythe same "places" (or loci) in chromosomes. Every living organism has allelic genes in pairs. Interaction of allelic genes can occur in several ways, which are called: codomination, overdominance, complete and incomplete dominance.
Allelic genes interact according to the principlefull dominance in the event that the action of the dominant gene completely blocks the action of the recessive. Incomplete dominance can be called a relationship in which a recessive gene is suppressed incompletely and takes, albeit minimal, participation in the formation of phenotypic traits.
Co-domination occurs ifallelic genes manifest their properties independently of each other. Probably the most revealing example of codomination is the ABO blood system, in which both A and B genes function independently of each other.
Overdomination is the increase in qualityphenotypic manifestations of the dominant gene in the event that it is "in conjunction" with the recessive. That is, if there are 2 dominant genes in one allele, then they appear worse than the dominant gene, which is "in conjunction" with the recessive gene.
Multiple Allelism
As already mentioned, every livingthere can be only two allelic genes, but alleles can be much more than two - this phenomenon is called multiple allelicism. Just say that only one pair of alleles can manifest phenotypic signs, that is, while some work, others rest.
Almost always homologous (identical)alleles are responsible for the development and manifestation of the same feature, but differ in the quality of its manifestation. Also, multiple alleles are inherent in various forms of gene interaction. That is, although they are responsible for the same feature, but, firstly, show it in different ways, and secondly, with the help of various methods (complete, incomplete dominance, and so on).
It would seem, why such confusion? It's simple - only one pair of homologous alleles can enter the germ cell of a living creature, but what is already available, the case already decides. It is through this that the variability of species that plays a major role in the evolution of living beings is achieved.
