A recessive allele is one whose expression of the phenotype is masked.
In order to know the meaning of the term recessive allele , the first thing we have to do is proceed to discover the etymological origin of the two words that give it shape:
– Allele is a neologism that was created in the 20th century and comes from Greek. Specifically, it derives from allello and means "two."
– Recessive , on the other hand, is a word of Latin origin that is the result of the sum of three clearly delimited components: the prefix re- , which means “backwards”; cessus , which can be translated as "walked" and the suffix -ivo , which is used to indicate an active or passive relationship.
What is a recessive allele
The notion of allele comes from allelomorph : that which can appear in different forms. In the field of biology, the value adopted by each gene that, in a pair, occupies the same space on the chromosomes that are homologous, is called an allele.
Recessive , for its part, is an adjective that in biology is applied to hereditary characteristics that are not expressed in the phenotype of the person who has them, although they can manifest themselves in the descendants of the individual in question.
Understanding what a recessive allele is leads us to the notion of a dominant allele and, above all, to what is known as dominance . The alleles that make up the same gene are related to each other: dominance is the masking that one allele (the dominant allele) achieves of the expression of the phenotype of the other allele (the recessive allele).
The recessive allele, in this way, is the one whose expression of the phenotype is masked . It should be noted that being dominant or recessive is relative: in a gene with three alleles, for example, one allele can be recessive with respect to another and dominant over the third. Recessive alleles are represented with lowercase letters and dominant alleles with uppercase letters.
Recessive alleles have to appear alone to manifest.
Its manifestation
To manifest themselves, recessive alleles must appear alone . Suppose that, in a flower, the color yellow is a recessive allele. In this way, for the flower to determine its yellow color, it must have only the alleles that express said shade. In the case of dominant alleles, however, they impose themselves by appearing in a single dose or a double dose and thus manage to express their characteristics .
When we talk about human beings, we have to explain that each gene is determined to have two alleles: one that comes from the father and another that comes from the mother. Starting from this we find the fact that it is said that the allele that establishes that the child has brown eyes is dominant, however, the one with blue eyes is recessive.
This means that if the couple is made up of a father and a mother with brown eyes, their baby will have brown eyes. In the event that one of the two has blue ones, it is most likely that the little one also has brown ones due to the dominant allele, unless he inherits the recessive alleles from other relatives.