chromosomes are DNA composite structures which, in turn, carry the genes of a living being, responsible for defining the particular physical characteristics of each individual.
Chromosomes are located in the nucleus of cells that make up a living being. You human beings have 46 chromosomes, divided into 23 pairs, being 44 autosomes and 2 sexual.
The chromosomes that form pairs are called counterparts and constitute the so-called diploid cells (2n).
All genetic information about an individual, such as hair color, eye color, physical structure, and other hereditary characteristics, is present in the person's DNA. Chromosomes serve to store all this information, condensing the genetic material to fit inside the cells.
Initially, the first scientist to observe chromosomes was the Swiss biologist Karl Wilhelm von Nägeli, in 1842. However, only with Thomas Hunt Morgan, in 1910, it was discovered that chromosomes are responsible for storing the genetic material of living beings.
Learn more about DNA meaning.
Chromosome structure
Chromosomes are formed by histones, proteins that form groups that are enclosed by DNA molecules. These sets are called nucleosomes and there can be several of these groups on a single DNA molecule.
Obviously, there are differences between the structure of the chromosomes of prokaryotes (bacteria, for example) and eukaryotes (humans, for example).
In the case of eukaryotes, each chromosome has a centimeter (its most condensed region) and, at this point, the sister chromatids are linked (the two “arms” that form a chromosome).
At the ends of the "arms" of the chromatids are special structures called telomeres, are responsible for maintaining the structural stability of the chromosome.
See also: meaning of chromatin and eukaryotic cell.
Chromosome Types
Chromosomes are not all the same, and their shape can vary according to the position of the “strangulation” made by the centrometer (connection point between the chromatids).
- Telocentric Chromosome: the centrometer is located at the terminal end of the chromosome.
- Acrocentric Chromosome: the centrometer is away from the center and close to one end, making one of the pairs of “arms” that make up the chromosome larger than the other.
- Submetacentric Chromosome: when the centrometer is just off the middle of the chromosome.
- Metacentric Chromosome: the centrometer is at the center of the chromosome, making all of your “arms” the same size.
See also: the meaning of genes.
Chromosomal Syndromes
A small change in the structure of chromosomes can trigger different types of syndromes and genetic mutations.
In the human species, for example, mutations in chromosomes can lead to physiological and biological disorders, such as Down's syndrome, Turner syndrome, Edwards syndrome, Klinefelter syndrome, among others.
