With technological advances, the human being has access to microscopic organisms that allow him to know life at a cellular level, which greatly favors studies in the health sciences, from something as elementary for life, as it is DNA, so it is always interesting to discover its dynamics and the elements that make it up, such as the chromosome and chromatin.
What is the Chromosome?
The organized structure within a cell that contains much of the genetic information of a living being is called a chromosome. The chromosome is made up of DNA and other proteins, its structure is X-shaped and perfectly visible during the cellular processes of meiosis or mitosis, through a microscope.
The name of chromosome comes from the Greek that means “body that is dyed”, whose origin derives from the end of the 19th century, and certain inks were used to be able to see them. But it was not until the 20th century, after the first investigations on DNA and after the establishment of Mendel’s laws, that the importance of the chromosome in inheritance and genetic transmission was discovered.
The chromosome is found in equal pairs among the members of the same species, which for the human species are 23 pairs of chromosomes. And its structure looks like two parallel arms, each one called a chromatid that contains the genes, and are joined by a centrometer, which, according to its location, allows us to establish three classes of chromosomes:
- Metacentric: where the centrometer is in the middle of the structure, leaving arms of similar length.
- Submetacentric: in them the centrometer is located a little removed from the center, so inaccurate and asymmetric arms are distinguished.
- Acrocentric: the union of the chromosome is at its ends, leaving long chromatid arms.
The structure of each chromosome originates from the various levels of DNA compaction, whose nucleus surrounds proteins called histones, which form the nucleosome; then this is connected by a fragment of DNA in a chain called a solenoid that coils and that in its folds gives rise to chromatin, which, when united and compacted, gives rise to an arm of the chromosome.
The function of the chromosome in living beings is to transmit the genetic information contained in the DNA of the cell of origin to its descendants, for which it originates cell replication, helping the growth of a new organism, repairing damaged cells and creation of reproductive cells.
According to the type of cell that it integrates, the chromosomes have two types: prokaryotes , which are found inside the nucleoid in a dispersed manner throughout the cell’s cytoplasm and only have one DNA chain; there are also eukaryotes , whose size is considerably larger than prokaryotes and contain the DNA chain in the form of a helix. The latter is in turn subdivided into two classes, according to the function they perform in the living being:
- Somatic or autosomal chromosomes : that define the physical aspects of the individual, but that are not related to its reproduction. Of them we found 22 pairs.
- Sex chromosomes or allosomes: it is the one that determines the biological gender of living beings. It corresponds to the 23rd pair that makes up the human being and that differs from XX if it is female or XY if it is male.
What is Chromatin?
Chromatin is the substance that makes up the chromosome, made up of proteins known as histones that, together with DNA and RNA, are compacted to join the cell nucleus that receives the name of nucleosome, and that later generate a structure in the shape of a necklace of pearls and they become solenoids; from there, they continue to compact until they form a rod and join their pair to become a chromosome.
Chromatin is found in eukaryotic cells with the genetic material before cell division occurs, that is, interphase. There are two types of chromatin:
- Heterochromatin: located far from the nucleus and shaped like a lump. There is inactivity in the DNA due to a high degree of condensation that does not allow the coding of the genetic material.
- Euchromatin: in it the DNA is active, thanks to the low density that facilitates the interaction of the genetic material.
The function of chromatin is related to the dynamics that achieves the compaction of the structure that will later become a chromosome, to also optimize the processes of transfer of genetic material, so it is modified and adapted throughout the cell cycle. .
Difference Between Chromosome and Chromatin
- Chromatin is a dynamic structure that participates in the compaction process of the chromosome, while the chromosome is the structure already formed within the cell that contains genetic information of a living being.
- The chromosome has the function of transporting the genetic material contained in the DNA; On the other hand, the chromatin has the purpose of forming the chromosome.
- The types of chromatin differ in their density and compaction capacity for DNA transmission. On the other hand, the types of chromosomes define the physical and sexual characteristics of individuals.