The chromosome composition of male somatic cells is

Cell chromosomes are a type of cell component that exists in both males and females. Cell chromosomes have a great influence on genetics. Many characteristics of children, even their gender, are determined by cell chromosomes. Cell chromosomes also have a certain structure and composition. Below, we will introduce the relevant knowledge of male somatic cell chromosomes in detail!

Chromosomes are substances in the cell nucleus that carry genetic information. They appear cylindrical or rod-shaped under a microscope and are mainly composed of DNA and protein. They are easily stained by alkaline dyes (such as gentian violet and acetic acid magenta) during the mitosis period of cells, hence the name.

In asexual species, all cells in the organism have the same number of chromosomes; in most sexually reproducing species, the chromosomes of the organism's somatic cells are distributed in pairs, containing two sets of chromosomes, which is called diploid.

Sex cells such as sperm and eggs are haploid, with half the number of chromosomes as somatic cells. The sex chromosome pair of male mammalian cells is XY, while that of females is XX. The sex chromosomes of birds, amphibians, reptiles, and some insects are different from those of mammals: males have ZZ, while females have ZW.

2. Chromosome Structure

The ultrastructure of chromosomes shows that chromosomes are composed of highly coiled DNA-histone fibers with a diameter of only 100 angstroms (Å, 1 angstrom = 0.1 nanometers). Each chromatid can be regarded as a double-helical DNA molecule. During interphase of mitosis, DNA unwinds to form infinitely stretched filaments, which are not easily stained by dyes. Under the microscope, they appear as an amorphous substance, called chromatin. During mitosis, DNA is highly coiled and presents a specific shape, which is easily stained by alkaline dyes and is called euchromatin.

The various banding techniques that came out after 1970 have made great contributions to the identification of chromosomes. After DNA denaturation, trypsin digestion or fluorescent staining, metaphase chromosomes can show light and dark bands arranged along the longitudinal axis. According to the characteristic marks on the chromosomes, each arm can be divided into several regions from the inside to the outside, and each region can be divided into several bands, and each band can be divided into several sub-bands. For example, "9q34.1" means the first sub-band of the fourth band in the third region of the long arm of chromosome 9. Since the number and width of each chromosome band are relatively constant, each chromosome and its fragments can be identified according to the different band types.

3. Chromosome Composition

The main chemical components of chromosomes are deoxyribonucleic acid (DNA) and proteins. There are two types of proteins on chromosomes: one is low molecular weight alkaline proteins, namely histones, and the other is acidic proteins, namely non-histone proteins. The types and content of non-histone proteins are not very constant, while the types and content of histones are very constant, and their content is roughly equal to that of DNA. Therefore, people have long speculated that histones play an important role in the formation of DNA-protein fibers. 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 fibers. The structural unit of the fiber is the nucleosome, which is the most basic unit of chromosome structure.