The significance of meiosis is to conserve the genetic material across the generations in sexually reproducing organisms. This process takes place during gamete formation and leads to the reduction of genetic material into half because after fertilization the genetic material doubles. Thus, this process is also called reductional division, particularly Meiosis I. The process of meiosis consists of two stages – Meiosis I and Meiosis II. Sperms and eggs are the gametes or sex cells that form after meiosis. Meiosis is a very important type of cell division in the life of an organism.
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What is Meiosis?
Meiosis is a type of cell division particularly found in sexually reproducing organisms. This is a specialized kind of cell division in which the chromosome number is reduced by half and haploid daughter cells are produced. This process is also known as “reductional division” as the ploidy of the cell gets reduced.
The gametes resulting from meiosis fertilize to form the zygote. The zygote further develops into the whole organism. Meiosis, thus ensures the production of the haploid phase in the life cycle of sexually reproducing organisms on the other hand fertilization restores the diploid phase. This process occurs during gametogenesis which refers to the formation of gametes in plants and animals.
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Stages of Meiosis
Meiosis involves two main stages which are Meiosis I and Meiosis II. These two main stages are classified into sub-stages which can be explained as follows.
Meiosis I
Meiosis I is particularly called “reductional division”. During this, the chromosomes are reduced by half. This process is divided into Prophase I, Metaphase I, Anaphase I, and Telophase I.
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Prophase I: It is a longer and more complex phase. It is further subdivided into five phases based on chromosomal behavior and these include Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.
- Leptotene: In this stage, the chromosomes can be seen under the light microscope. The chromosomes get condensed through this stage.
- Zygotene: The chromosomes start pairing together and this process of association is called synapsis. Such paired chromosomes are called homologous chromosomes. The complex structure that forms due to this pairing is called as synaptonemal complex.
- Pachytene: In this stage, recombination nodules appear which are the sites at which crossing over occurs between non-sister chromatids of the homologous chromosomes.
- Diplotene: During this stage, the homologous chromosomes get separated except at the site where the crossing-over has occurred. At the site of crossing over X-shaped structures are visible which are called chiasmata.
- Diakinesis: The chiasmata disappear and chromosomes get completely condensed. Also, the meiotic spindle assembles for the separation of homologous chromosomes. At the end of this stage, the nucleolus disappears and the nuclear envelope breaks down.
- Metaphase I: Here the arrangement of chromosomes is observed on the equatorial plate.
- Anaphase I: The homologous chromosomes get separated and the sister chromatids remain associated at their centromeres.
- Telophase I: The nuclear membrane and nucleolus reappear and finally the cell divides.
After Meiosis I, the cells undergo a short stage called as Interkinesis during which no DNA replication occurs.
Meiosis II
The two daughter cells resulting from Meiosis I undergo Meiosis II. This stage is referred to as “equational division” because it is very similar to mitosis where the chromosome number remain same. It is further divided into Prophase II, Metaphase II, Anaphase II, and Telophase II.
- Prophase II: Nuclear membrane disappears at the end of this stage and the chromosomes get condensed.
- Metaphase II: In this stage, the chromosomes get aligned at the equator. The spindle fibres attach to the kinetochores of the sister chromatids.
- Anaphase II: Centromere of each chromosome splits and the sister chromatids start moving to the opposite poles of the cell. This happens because the spindle fibers attached to the kinetochores gets shortened.
- Telophase II: The chromosomes again get surrounded by a nuclear envelope and the cytokinesis leads to the formation of four haploid daughter cells. Telophase II marks the end of meiosis.
Diagram of Meiosis
The labeled diagram of meosis is given below:
Features of Meiosis
Meiosis consists of two sequencial cycles of nuclear and cell division called Meiosis I and Meiosis II but only one cycle of DNA replication.
- In meiosis I the chromosome number is reduced to half and meiosis II is similar to the mitotic division.
- Meiosis I is particularly known as reductional division.
- Four haploid daughter cells are formed in each cycle of meiotic cell division.
- Recombination of genetic material takes place during meiosis.
- Meiosis occurs in reproductive organs which results in the formation of gametes.
Significance of Meiosis
The significance of meiosis can be understood as follows:
- Sexual Reproduction: Meiosis creates such cells that further result in the formation of gametes. Thus, the reduction in chromosome number is important as without it, the fusion of gametes during fertilization would result in offspring with twice the normal number of chromosomes.
- Genetic Diversity: Meiosis results in new combinations of genetic material in each of the four daughter cells. This happens due to the exchange of DNA between homologous chromosomes that leads to a range of genetic variations.
- Gamete Production: Meiosis results in the formation of sex cells or gametes which are responsible for sexual reproduction. It maintains the constant number of chromosomes in the organisms as in gametes the chromosomes get reduced to half and after the fertilization of gametes the zygote contains a complete set of chromosomes.
Conclusion – Significance of Meiosis
Meiosis is a very significant process in the life of a sexually reproducing organism because it is responsible for the formation of gametes. It results in the conservation of the specific chromosome number of each species across generations. In meiosis, recombination of genetic material takes place due to which the gametes are haploid but not identical. This recombination is responsible for the genetic variability observed in the organisms which is required for the survival of these organisms.
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FAQs on Significance of Meiosis
What is the other Name of Meiosis?
Meiosis is also known as “reductional division”. This is because the number of chromosomes gets reduced by half in this process and the resulting cells are haploid.
What are the Two main Stages of Meiosis?
Meiosis is divided into two main stages which are Meiosis I and Meiosis II. Meiosis I is also called “reductional division” while Meiosis II is called “equational division”.
What is Meant by Karyokinesis and Cytokinesis?
The division of the nucleus is called karyokinesis and the division of cytoplasm is called cytokinesis. During cell division first karyokinesis takes place and then cytokinesis happens.
What are the Substages of Prophase I?
The Prophase I is the longest phase of meiosis I. It consists of five stages which are Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.
Which Cells undergo Meiosis in Eukaryotes?
In eukaryotes, the germ cells undergo meiosis. The germ cells are the sex cells that are involved in sexual reproduction.
What is the Significance of Meiosis?
Meiosis helps in maintaining the chromosome number of the organism. It is responsible for genetic diversity in an organism.