According to DigoPaul, concordance is called the consent, consent or correspondence that exists between two elements. The term, which comes from the Latin concordantia, can be used in various contexts.
In the field of grammar, concordance is the formal congruence that must be registered between the inflectional information of those words that are linked at the syntactic level.
What grammatical concordance does is establish the grammatical relationship between the different constituents. For this he appeals to cross references that lead each word to adopt a certain form according to the features determined by another word: both, due to these features, agree.
The number and gender are two of the features that allow the development of grammatical agreement, which can be verbal, nominal or otherwise. To be expressed correctly, there must be a concordance between the articles, adjectives and nouns that make up a sentence, to cite a case.
This means that, if we are going to use the noun “house”, for example, we will also have to use a feminine and singular article (“la”) and an adjective that is concordant (such as “big”): “The big house”. Expressions such as “The big house”, “The big house” or “The big house” have no agreement.
In music, concordance is the proportion maintained by the various voices that, in a composition, sound together.
We speak of genetic concordance, on the other hand, to refer to the existence of the same phenotypic trait in a pair of individuals, usually monozygotic twins, although it can also be any pair and individuals that are in the group that is being studied.
The term phenotype is used in the field of genetics, but also in other areas of study of biology, to refer to the expression of the genotype (the genetic information in the form of DNA of a given organism), taking into account an environment determined. Phenotypic traits can be seen both in the body and in the behavior of individuals; Furthermore, the characteristics studied are not always visible, something that can be exemplified with enzymes.
In other words, genetic concordance can be defined as the probability that the two members of a given pair have the same characteristic, or that one of them has a characteristic that has been observed in the other.
Studies focused on monozygotic twin brothers seek to find the genetic concordance rate of phenotypic traits, generally diseases, to know what percentage of these appear in the environment and how much it reaches them through the genetic load. Since the DNA of monozygotic twins is identical, they are expected to suffer from the same genetic diseases; Although this is true for monogenic, not so in the case of polygenic.
Some twin studies have aroused controversial reactions, such as those that sought genetic agreement with respect to the intelligence or homosexuality of individuals.
When part of the study consists of modifying the position of the DNA directly, altering a simple nitrogenous base, the agreement is understood as the percentage of identical bases. In theory, this should be 100% in two samples from the same person or from monozygotic twins, but it is usually around 99% due to certain somatic mutations (changes one nucleotide or in the DNA organization) and artifacts of the tests.
That said, it is understood that genetic agreement can also serve as a method of rating the accuracy of various tests. Using this procedure, it is expected that between parents and children there is close to 50% concordance, since each individual inherits half of the DNA of each parent.