The set of the various genes operating as a unit and which are responsible for certain signs enters a genotype. Diploidic organisms differ from haploid in two genes which are responsible for each sign – these genes are called allelic. What is represented by allelic genes and as they interact among themselves?
Allele: definition and concept
To alleles call one of gene forms which defines one of many options of development of any given sign. Usually alleles are divided into prepotent and recessive – the first completely corresponds to a healthy gene whereas recessive includes various mutations of the gene, resulting in "malfunction" in its work. Also the multiple allelizm at which geneticists allocate more than two allelya meets.
At a multiple allelizm the diploidic organisms possess two alleles inherited from parents in different combinations.
The organism with identical allelic genes is considered homozygous, and an organism with different alleles – heterozygotic. The heterozygote differs in manifestation of prepotent sign in a phenotype and hiding of recessive. At complete dominance the heterozygotic organism possesses a prepotent phenotype whereas at incomplete domination its phenotype is intermediate between recessive and to prepotent alleles. Thanks to couple of homologous alleles getting to an organism gamete, types of living beings are changeable and capable to evolution.
Interaction of allelic genes
There is only one possibility of interaction of these genes – at absolute domination of one allelya over the second, remaining in a recessive state. Fundamentals of genetics contain no more than two types of interaction of allelic genes – allelic and nonallelic. As allelic genes of each living organism are always present at couple, their interaction can happen in the way of a kodominirovaniye, overdominance and also complete and incomplete dominance.
Only one couple of allelic genes is capable of manifestation of phenotypical signs – while some have a rest, others work.
Interaction of alleles at complete dominance happens only when the prepotent gene completely blocks recessive. Interaction at incomplete domination is carried out at incomplete suppression of the recessive gene which is partially participating in formation of signs of a phenotype. Kodominirovaniye occurs at separate manifestation of properties of allelic genes whereas overdominance represents increase of quality of phenotypical signs of the prepotent gene which is together with a gene recessive. Thus, two prepotent genes which are in one allele will be worse shown, than the prepotent gene complemented with recessive.