When two different alleles are found in the genotype and both are expressed, we can speak of co-dominance.
In order to fully understand the meaning of the term co-dominance , it is necessary, first of all, to discover its etymological origin. In this case, we can state that it is a word of Latin origin that is the result of the sum of four very well-defined parts:
-The prefix «con-«, which can be translated as «together» or «everything».
-The verb "dominare", which is synonymous with "to have under one's power."
-The particle «-nt-«, which is used to indicate «agent».
-The suffix "-ia", which is used to indicate "quality."
Codominance concept
The genetic data that, according to its allelic composition, a certain organism has in its deoxyribonucleic acid ( DNA ) is called a genotype . Allelic , on the other hand, comes from allele : each alternative form that the same gene can adopt according to its sequence, which is located in the same place on the homologous chromosomes.
Codominance is a situation that occurs when two different alleles are found in the genotype and both are expressed. In this state, the expression of both alleles results in a phenotype (the manifestation of the genotype that varies according to the environment) with characteristics of both.
Therefore, it can be established that co-dominance is a type of genetic inheritance that has the characteristic that dominant characteristics are inherited from both parents.
Codominance is a type of genetic inheritance.
An example
A clear example to understand codominance is the one that establishes that an individual, in relation to his blood group, who has an allele A and an allele B will have an AB blood type. Of course, because the aforementioned alleles are co-dominant with each other.
With co-dominance, therefore, the expression of a gene in a heterozygous organism is equivalent to that of its peer. Heterozygotes, in this way, present two alleles of the same gene in relation to a certain trait. In incomplete dominance , however, the two alleles are also expressed but in a genotype that presents intermediate characteristics.
More cases of codominance
It can be said that, in heterozygotes, there are two alleles that are expressed but do not join together . Suppose that a co-dominant cross is made between two species of horse: one black and the other brown. The result of the cross will be a horse with black and brown spots since the two co-dominant alleles are expressed simultaneously.
Similarly, a flower A of yellow color and a flower B of blue hue, in a crossover with co-dominance, will allow the creation of a flower AB whose color will be yellow with blue spots: both co-dominant characters appear expressed.
In addition to all of the above, it is important to know that co-dominance as such is considered to have been a discovery, a theory, established by the biologist and writer Teresa Audesirk (1950). Apparently he raised the same point forcefully in his work titled "The Life of the Earth", thus taking a great step in the field of biology that has allowed for a lot of progress in biology in recent years. However, it is considered that it has not had the recognition it deserved.