The reproductive function of the body is carried out in the process of combining two gametes (germ cells) during the emergence and subsequent development of the zygote of the daughter organism - a fertilized egg. Sexual parent cells have a specific set of n-chromosomes. It is called haploid. The zygote, taking these sets into itself, becomes a diploid cell, i.e. the number of chromosomes there is 2n: one maternal and one paternal. The biological significance of meiosis as a special division into cells is that it is thanks to it that a haploid cell is formed from diploid cells.
Definition
In biology, meiosis is usually called a type of mitosis; due to its diploid somatic cells of the gonads are divided into 1n gametes. When the nucleus is fertilized, gamete fusion occurs. Thus, the 2n chromosome set is restored. The significance of meiosis is to ensure the intrinsic safety of the chromosome set and the corresponding amount of DNA inherent in each species of living organisms.
Description
Meiosis is a continuous process. It consists of 2 types of division, successively following each other: meiosis I and meiosis II. Each of the processes, in turn, consists of prophase, metaphase, anaphase, telophase. The first division of meiosis, or meiosis I, halves the number of chromosomes, i.e. the phenomenon of the so-called reduction division occurs. When the second stage of meiosis, or meiosis II, occurs, the haploid cells are not threatened with a change, it persists. This process is called equational division.
All cells that are in the stage of meiosis carry some information at the genetic level.
- The prophase of meiosis of the first is the stage of gradual spiraling of chromatin and the formation of chromosomes. At the end of this highly complex action, the genetic material is present in its original form - 2n2 chromosomes.
- There is a metaphase - there comes the maximum level of spiraling. Genetic material is still unchanged.
- Anaphase of meiosis is accompanied by reduction. Each pair of parent chromosomes gives one of its daughter cell. Genetic material varies in composition since the number of chromosomes has become half as much: 1n2 chromosomes per cell pole.
- Telophase - the phase when the nucleus is formed, cytoplasms are separated. Daughter cells are created, there are 2 of them, and 2 chromatids in each. Those. the set of chromosomes in them is haploid.
- Then there is interkinesis, a short respite between the first and second stage of meiosis. Both daughter cells are ready to enter the second stage of meiosis, which proceeds according to the same mechanism as mitosis.
The biological significance of meiosis lies, therefore, in the fact that in its second stage, as a result of complex mechanisms, 4 haploid cells — 1n1 chromosomes — are already formed. That is, one diploid mother cell gives birth to four - each has a haploid chromosome set. In one phase of meiosis of the first degree, the genetic material is recombined, and in the second stage, the chromosomes and chromatids move to different poles of the cell. These movements are a source of variability and various intraspecific combinations.
Summary
So, the biological significance of meiosis is really great. First of all, it should be noted as the main, main stage of the gamete genesis. Meiosis ensures the transfer of genetic information of species from one organism to another, provided that they reproduce sexually . Meiosis makes it possible to occur intraspecific combinations, because daughter cells differ not only from parent cells, but also differ from each other.
In addition, the biological significance of meiosis is also in ensuring a decrease in the number of chromosomes at the moment when germ cells are formed. Meiosis provides their haploidy; at the moment of fertilization in the zygote, the diploid composition of chromosomes is restored.