Definition: what is the phenotype?
The phenotype refers to the visible expression of genes. In other words, all the characteristic traits of a person, both at the macroscopic scale (the color of his eyes, his hair, his hair, the tone of his voice, his morphology, etc.) thatat the cellular level (blood phenotype).
It can also be influenced by epigenetic factors, such as smoking, which can modify the expression of genes, or by environmental factors, such as exposure to the sun, which induces a tan and modifies the original “light skin” phenotype, or the intensive practice of an activity physical.
The importance of phenotypic variations
Fact, an individual’s phenotype can change over time, depending on his environment: the hair becomes lighter in the sun, the body language becomes more flexible depending on who he is talking to, etc. These phenotypic variations due to genetic variations are fundamental in evolution by natural selection.
What is the difference between phenotype and genotype?
Genotype can only be distinguished by looking at DNA. It contains the hereditary information in the genome. While the phenotype can be known by observing the external physical appearance of a person. To summarize, the genotype contains the genetic heritage of an individual, and the phenotype, as noted earlier, expresses it.
Note: all people with the same genotype will not necessarily have the same physical characteristics, because the appearance and the other components of the phenotype evolve according to the environment. Part of the genes may never have the opportunity to express themselves in an individual, and reappear later in its lineage.
What is the blood phenotype?
The different blood phenotypes are defined according to the antigens present on the surface of red blood cells. Three main phenotypes are generally distinguished:
- the phenotype called “ABO”, which defines the letter of the blood group (A, B, AB or O).
- the rhesus phenotype, determined by the presence or absence of the Rh1 antigen, which allows you to add a “plus” or a “minus” behind the letter of the blood group (A+, B-, etc.).
- and the KEL phenotype, which is defined by the presence of K antigens on the surface of red blood cells.
For each of the phenotypes, it is possible to determine the presence of antibodies directed against the “absent” antigens. For example, a group A individual will possess anti-B antibodies. The determination of blood phenotypes is very important and makes it possible to define transfusion rules.
What is the link between phenotype and rhesus?
Rhesus is therefore one of the three phenotypes that go into determining a person’s blood type. It is for example essential to determine it before or at the beginning of the pregnancy to avoid an incompatibility which could be fatal. If the mother is “rhesus minus” (Rh-) and her child is rhesus plus (Rh+), her anti-rhesus antibodies can cross the placental barrier and risk attacking the red blood cells of the fetus…
The phenotype is often easier to measure than the genotype. It can be observed at different levels:
- at the molecular level: molecular phenotype ;
- at the cell level: cellular phenotype ;
- and at the organizational level: macroscopic phenotype.
Richard Dawkins is at the origin of a new concept of phenotype, the extended phenotype, which takes into account all the impacts of genes on the organism and its environment.