reproductive function of the body is carried out in the process of combining two gametes (sex cells) in the event and the subsequent development of the child organism zygote - a fertilized egg.In sex parent cells have a certain set of n-chromosome.He called haploid.Zygote as taking a set of these becomes a diploid cell, i.e.where the number of chromosomes 2n: one maternal and one paternal.The biological significance of meiosis as a special division of cells is that thanks to him, haploid cells produced from diploid cells.
definition
meiosis in biology is called a kind of mitosis;due to its diploid somatic cells of the genital glands are divided into 1n gametes.When the kernel is fertilized, the merging of gametes.Thus, it is recovering 2n chromosome set.Meaning of meiosis is inherent securing each kind of living organisms chromosomes and an appropriate quantity of DNA.
Description
meiosis - the process is continuous.It consists of 2 kinds of dividing successively consecutive: meiosis I and meiosis II.Each of the processes, in turn, consists of prophase, metaphase, anaphase, telophase.The first meiotic division, or meiosis I, halves the number of chromosomes, iethe phenomenon of the so-called reduction division.When is the second stage of meiosis, or meiosis II, haploid cells does not threaten the change, it is saved.This process is called equational division.
All cells in the stage of meiosis, carry some information on the genetic level.
- Prophase of meiosis of the first - stage of gradual spiraling chromatin and the formation of chromosomes.At the end of this very complex operation genetic material present in the original form - 2n2 chromosomes.
- metaphase comes - comes and the maximum level of helix.Genetic material remains unchanged.
- Anaphase meiosis followed by reduction.Each pair of parental chromosomes gives one of its daughter cells.Genetic material is changed in composition, asnumber of chromosomes was only half: on each pole cells accounted for chromosome 1n2.
- Telophase - phase, when the core is formed, separated cytoplasm.The daughter cells are created, they are 2 and each with 2 chromatids.Ieset of chromosomes in haploid them.
- Then there interkinesis, short break between the first and second stage of meiosis.The two daughter cells are ready to enter the second stage of meiosis, which occurs by the same mechanism as mitosis.
biological significance of meiosis is, therefore, that in its second step by complex mechanisms form haploid cells for 4 - 1n1 chromosomes.That is, one diploid mother cell gives life to four - each haploid chromosome set.In one phase of the first meiosis degree recombines genetic material, and the second step is carried out the movement of chromosomes and chromatids to different poles of the cell.These movements - the source of intraspecific variability and the different combinations.
Results
Thus, the biological significance of meiosis, really great.First of all, it should be noted as the main, the main stage of the genesis of gametes.Meiosis is provided transfer of genetic information from one organism species to another, provided that they reproduce sexually.Meiosis allows intraspecific combinations occur, asdaughter cells differ not only from the parent, but also differ.
addition, the biological significance of meiosis consists in providing reducing the number of chromosomes in the moment when the formed germ cells.Meiosis ensures their haploid;at the time of the fertilization the zygote diploid chromosome structure is restored.
