What are the components of chromosomes?

The rapid development of modern medicine has enabled medical scientists to continuously unlock the secrets of genetics. This is the research direction of chromosomes. Chromosomes are the genetic material of the human body. For everyone, this is the genetic basis of genes. With the advancement of medical technology, the structural organization of chromosomes is becoming clearer and clearer. Let’s take a look at the components of chromosomes. I hope those who are interested can learn more about it.

Chromosomes are objects with genetic properties inside cells. They are easily stained dark by alkaline dyes, so they are called chromosomes (chromatin). Their essence is deoxynucleotides. They are structured filaments inside the cell nucleus composed of nucleoproteins, which can be stained with alkaline dyes. They are the carriers of genetic material genes.

Element:

The main chemical components of chromosomes are deoxyribonucleic acid (DNA) and protein. There are two types of proteins on chromosomes: one is low molecular weight alkaline protein, namely histone, and the other is acidic protein, namely non-histone protein. The types and contents of non-histone proteins are not very constant, while the types and contents of histones are very constant, and their contents are roughly equal to those of DNA. Therefore, people have long speculated that histones play an important role in the formation of DNA-protein filaments. Based on biochemical data, especially electron microscopy, Kornberg first proposed the beads on a string model in 1974 to explain the structure of DNA-protein filaments. The structural unit of the filament is the nucleosome, which is the most basic unit of chromosome structure.

The core of the nucleosome is a flat spherical octamer composed of two molecules of each of the four histones (H2A, H2B, H3 and H4). We know that DNA molecules have a typical double helix knot, and a DNA molecule is like a long double helix fiber. A chromosome contains one DNA molecule. The DNA double helix is ​​coiled about 1.75 times on the surface of each histone octamer molecule, and its length is equivalent to 140 base pairs. The 8-mer histone protein and the DNA molecules coiled on its surface together form the nucleosome. Between two adjacent nucleosomes, there is a DNA connecting line about 50 to 60 base pairs long. Between adjacent connecting lines is a molecule of the fifth histone (H1). Densely clustered nucleosomes form fibers of about 100 angstroms in the nucleoplasm. This is the "primary structure" of chromosomes. Just like a string of beads, DNA is the rope and histones are the beads. This is called the "bead-on-rope model" of chromosomes.