What is a phenotype? Concept, main features, interaction with the genotype

The word "phenotype" is of Greek origin and is translated (verbatim) "I find out," "I am." What is the practical significance of this concept?

What is a phenotype? Definition

A phenotype is understood as a set of characteristics that are inherent in an individual at a particular stage of development. This set is formed on the basis of the genotype. Diploid organisms are characterized by the manifestation of dominant genes. More precisely defining what a phenotype is, it is necessary to talk about the totality of internal and external signs of the organism that were acquired in the process of individual development (ontogeny).

General information

Despite a fairly precise definition of what a phenotype is, its conception has a number of uncertainties. Most of the structures and molecules that are encoded by the genetic material are not found in the external appearance of the body. They are part of the phenotype. An example is the phenotype of human blood. In this regard, according to several authors, the definition should include those characteristics that can be obtained with the use of diagnostic, medical or technical procedures. A more radical further expansion may contain the acquired behavior, and, if necessary, the influence of the organism on the habitat and other organisms. So, for example, cutters and a dam of beavers can be taken for their phenotype.

Main characteristics

Defining what a phenotype is, we can talk about some "removal" of genetic information towards environmental factors. At first approximation, two characteristics should be considered:

1. Mentality of the phenotype. This sign indicates the number of directions of "removal", which characterizes the number of environmental factors.
2. The second sign indicates the level of sensitivity of the phenotype to the surrounding conditions. This degree is called the range.

In a complex these characteristics testify to the richness and variety of the phenotype. The more multi-dimensional the aggregate of individual characteristics, the more sensitive the symptoms and the further they are from the genotype, the richer it is. So, for example, if we compare the phenotype of a bacterium, ascarids, frogs, humans, then "wealth" in this chain increases. This means that the phenotype of man is richer.

Historical reference

In 1909, Wilhelm Johansen (Danish scientist) for the first time - in conjunction with the concept of the genotype - proposed the definition of the phenotype. This made it possible to distinguish heredity from the result of its realization. The idea of differences can be traced in the works of Mendel and Weismann. In this case, the latter distinguished somatic and reproductive cells in multicellular organisms. The chromosome set obtained from the parents is contained in the cell nuclei. Chromosomes carry a complex of genes, characteristic for a particular species in general and a particular organism in particular. The genes contain information about proteins that can be synthesized, as well as mechanisms that, in fact, determine and regulate the synthesis. What happens in this case? In ontogeny, genes are sequentially switched on and those proteins that are encoded by them are synthesized. As a result, all the properties and attributes of the organism that make up its phenotype are formed and developed. In other words, it turns out a certain "product" from the realization of the genetic program contained in the genotype.

The influence of external conditions on the development of individual characteristics

It should be noted that the genotype is not an unambiguous factor that determines the phenotype. To some extent, the formation of a set of individual characteristics will also depend on the environment of stay, that is, on external factors. In different conditions the phenotypes have a sharp difference. So, for example, the species of butterflies "arashnia" a year gives two offspring. Those individuals that emerged from the overwintered pupae (spring), differ sharply from those that appeared in the summer. The phenotype of a plant can also differ. For example, in the open space the pines are spread, and in the forest they are slender and high. In the water buttercup the shape of the leaf depends on where it stays - in the air or in the water.

The relationship between phenotypes and genotypes

The ability to change, which is provided by the genetic program, is called the rate of reaction. As a rule, the more diverse the conditions in which the species lives, the wider this norm. In the case when the environment is sharply different from that to which the species is adapted, there is a disruption in the development of organisms, and they perish. The signs of a phenotype do not always reflect recessive alleles. But at the same time they are saved and can move to the offspring. This information allows you to better understand the evolutionary process. In natural selection only phenotypes are involved, the offspring are transmitted and remain further in the population genotypes. Interaction is not limited to the relationship between recessive and dominant alleles - many genes interact with each other.