Chromosomes are structural and functional elements of a human cell that contain genes. These units of the cell row are capable of staining at the time of cell division. Chromosomes have the form of sticks, threads, loops, etc. These elements are heterogeneous along their length. They consist of a centromere, a short and a long shoulder, a secondary constriction, a satellite, a spindle thread, and chromonemes. The location of such a part of the chromosome as the centromere affects the shape of the unit of the cell row itself. In the event that this part is located at the end of the structural-functional element, then it will be rod-shaped. Finding such a part as a centromere in the middle affects the fact that the chromosome takes the form of an equal arm hairpin. If the considered part is located to the side of the center, then the structural-functional element becomes a hairpin with different shoulders.
In general, there are 4 types of chromosome structure. The first type is telecentric structural and functional elements. The second is acrocentric (the second shoulder is very short and almost imperceptible). The third type is submetacentric chromosomes, the shape of which resembles the letter "L". Finally, the fourth type is metacentric. Chromosomes of this type have so-called shoulders, which are equal in length. In addition, such elements resemble the letter and at the same time the symbol of victory "V".
It should be noted that each nucleated somatic human cell contains twenty-three pairs of chromosomes that are linear. In addition, there is a large number of copies of mitochondrial DNA (deoxyribonucleic acid).
It is worth saying a few words about the sexual structural and functional elements of a human cell. These are the Y and X chromosomes. The first contains approximately 58 pairs of nitrogenous bases, carries 78 genes and at the same time has a high mutation rate due to the environment in which it is located. This sex chromosome can only be transmitted through sperm. They, in turn, are subject to a huge number of cell divisions that occur during gametogenesis. The sperm site is a highly oxidizing testis environment that stimulates the amplification of a process such as mutation. The second chromosome has approximately 150 million pairs of nitrogenous bases. It carries almost 1,400 genes. Men have one X and one Y chromosome. Women have a different "set." They have two X chromosomes. One of them goes to the girl from her mother, and the second is inherited from her father’s mother, i.e. from my grandmother on my father’s side.
Often questions arise about which chromosomes are called homologous and non-homologous. The answer is as follows. So, there are homologous chromosomes. These are paired structural and functional elements located in a diploid cell. Homologous chromosomes are distinguished by the fact that each of them is inherited from one and the other parent. Such elements have a similar nucleotide sequence along their entire length. This means that homologous chromosomes have the same genes that are located in the same sequence. It is worth noting that studying this topic is not only interesting, but also very useful in life, because it is better to know as much as possible about your body.
It should be added that homologous chromosomes constantly have the same type. For example, they can be whole-centric, sub-metacentric, acrocentric, metacentric. Non-homologous chromosomes contain genes that are dissimilar. In addition, these structural and functional elements are not conjugated in meiosis. Non-homologous chromosomes independently combine in a cell. This has been proven while studying the characteristics of inheritance of traits. Also, this information was obtained using a direct cytological method.
The information listed above will help to have a basic understanding of the chromosomes in general.