The ability to transmit genetic information is very important for procreation. Features of the chromosomal set of the male reproductive cell in the future after conception determine the inheritance of certain characteristics. This article will tell you about how many chromosomes the nucleus of the sperm contains.
Features of the structure of the male reproductive cell
Genetic information that is inherited by genus is encrypted in individual genes found on chromosomes.
The very first ideas of scientists about the chromosomes that are inside human cells appeared in the 70s of the XIX century. To date, the scientific world has not come to a consensus about which of the researchers discovered chromosomes. At various times, this discovery was "assigned" to ID Chistyakov, A. Schneider and many other scientists. However, the term "chromosome" was first suggested by the German histologist G. Waldeyer in 1888. The literal translation means "colored body", since these elements are rather well colored with basic dyes during research.
Most of the scientific experiments that clarified the definition of the structure of chromosomes were carried out mainly in the 20th century. Modern researchers continue scientific experiments aimed at accurately deciphering the genetic information that is contained in chromosomes.
For a better and simpler understanding of how the chromosome set of the male reproductive cell is formed, let's touch on biology a little. Each sperm consists of a head, a middle part (body) and a tail. On average, the length of the male cell to the tail is 55 µm.
The sperm head is elliptical. Almost all of its internal space is filled with a special anatomical formation, which is called the nucleus. It contains chromosomes - the main structures of the cell that carry genetic information.
Each of them contains a different number of genes. So, there are more and less gene-rich areas. Scientists are currently conducting experiments to study this interesting feature.
The main component of each chromosome is DNA. It is in it that the main genetic information is stored, inherited from parents by their children. Each of these molecules contains a certain sequence of genes that determine the development of various traits.
The DNA chain is quite long. In order for chromosomes to be microscopic in size, DNA strands are twisted strongly. Recent genetic studies have determined that special proteins are also needed to twist DNA molecules - histones, which are also found in the nucleus of the germ cell.
A more detailed study of the structure of chromosomes showed that, in addition to DNA molecules, they also consist of protein. This combination is called chromatin.
In the middle of each chromosome there is a centromere - this is a small section that divides it into two sections. This division determines the presence of a long and short arm in each chromosome. Thus, when examined under a microscope, it has a striated appearance. Each chromosome also has its own serial number.
The total chromosome set of a living organism is called a karyotype. In humans, it is 46 chromosomes, and, for example, in the fruit fly Drosophila only 8. The structural features of the karyotype determine the inheritance of a certain set of different traits.
Interestingly, the formation of sex chromosomes occurs even during the period of intrauterine development. The fetus, which is still in the mother's womb, is already forming sex cells that it will need in the future.
Sperm acquire their activity much later - during puberty (puberty). At this time, they become already quite mobile and capable of carrying out the fertilization of eggs.
Haploid set - what is it?
To begin with, you need to understand what experts mean by "ploidy". In simpler terms, this term means multiplicity. Scientists mean the total number of such sets in a particular cell by ploidy of a chromosome set.
Speaking about this concept, experts use the term "haploid" or "single". That is, the nucleus of the sperm contains 22 single chromosomes and 1 sex. In this case, each chromosome is not paired.
The haploid set is a distinctive feature of the sex cells. It was not conceived by nature by accident. During fertilization, part of the inherited genetic information is transmitted from the paternal chromosomes, and part from the maternal. Thus, the zygote obtained in the process of fusion of germ cells has a complete (diploid) set of chromosomes, in the amount of 46 pieces.
Another interesting feature of the haploid set of sperm is the presence of a sex chromosome in it. It can be of two types: X or Y. Each of them further determines the sex of the unborn child.
Each sperm contains only one sex chromosome. It can be either X or Y. The egg cell has only one X chromosome. With the fusion of germ cells and the unification of the chromosome set, various combinations are possible.
- XY... In this case, the Y chromosome is inherited from the father, and X from the mother. With this combination of sex cells, a male body is formed, that is, a couple in love will soon have an heir.
- XX... In this case, the child "receives" the X chromosome from the father and a similar one from the mother. This combination ensures the formation of the female body, that is, the birth of a little girl in the future.
Unfortunately, the process of inheritance of genetic information is not always physiological. Quite rare, but certain pathologies are encountered. This occurs when only one X chromosome is present in the zygote formed after fertilization (monosomy), or, conversely, their number increases (trisomy). In such cases, children develop rather severe pathologies, which further significantly worsen their quality of life.
Down's disease is one of the clinical examples of pathologies associated with a violation of the inheritance of the chromosome set. In this case, a certain "failure" occurs in 21 pairs of chromosomes, when the same third is added to them.
A change in the chromosome set in this situation also contributes to a change in inherited traits. In this case, the baby has certain developmental defects, and the appearance changes.
Human genome
For the normal functioning of each somatic cell of our body, 23 pairs of chromosomes are needed, obtained by it after the fusion of the genetic material of the maternal and paternal cells. The entire set of such acquired genetic material is called the human genome by genetic scientists.
The study of the genome allowed specialists to determine that the human chromosome set includes the sequence of more than 30,000 different genes. Each of the genes is responsible for the development of a specific trait in humans.
A specific gene sequence can thus determine the shape of the eyes or nose, hair color, finger length, and many other traits.
For what is transmitted to a person with genes, see the next video.
