Meaning of somatic cell
Every cell in a multicellular organism is called a somatic cell, except gametes. Therefore, somatic cells represent all cells in the body that have the complete set of genes, called diploid. The term “somatic” means “corporeal”, from the Greek: s?matikós.
Thus, in general, in multicellular organisms it is possible to identify two different types of cells: somatic and reproductive cells, called gametes.
Differences between Somatic and Reproductive Cells
The main difference between somatic cells is the number of chromosomes, that is, the number of DNA fragments that make up the set of genes of the species. In humans, the gene pool of somatic cells consists of 46 chromosomes, which is why they are called diploid (2n).
Consequently, human reproductive cells (sperm in men and eggs in women) have 23 chromosomes and are called haploid.
This number of chromosomes is constant in all beings of the same species and is one of the characteristics that distinguishes them from others. Therefore, the somatic cells of different individuals of the same species express basic characteristics in the body constitution of each one, which can lead to their identification as a specific group.
Another difference is due to the process in which they originate. Somatic cells are formed through cell division called mitosis, in which the parent cell gives rise to two daughter cells, with the same number of genetic material as the parent cell.
Reproductive cells are formed through meiosis, which is a division mechanism in which the original cell derives from four other daughters, with half the number of chromosomes in the initial cell, that is, this division divides half the gene pool.
Why do somatic lineages differ from reproductive ones?
In multicellular organisms, development and growth are separate from reproductive functions. A population of germ cells is specialized for reproduction and, evolutionarily, the rest of the cells, the somatic cells, provide a compartment or structure to house these reproductive cells.
Another aspect that differentiates body and reproductive cells is sexual reproduction, because what keeps the number of chromosomes of the species constant is the reduction in the number of chromosomes in the sexual lineage, because when the exchange of genetic material occurs, this the number is retrieved.
However, in unicellular organisms, the genetic programming exists for each cell to grow and divide, because cell division represents reproduction, which is responsible for increasing the number of individuals in the species.
Therefore, all the originating cells are identical and there is no variation in the number of genes among them naturally.