What is Meiosis?
Meiosis is a process of cell division which is necessary for eukaryotes in sexual reproduction. Meiosis is the process in which genetic materials are combined between two parent cell donors and is responsible for providing genetic variation among organisms. Meiosis produces cells called gametes in animals and some plants or spores in fungi and some plants. Gametes are typically referred to as sperm and egg cells.
Process of Meiosis
Meiosis follows the same basic process as mitosis but has some important differences. First is that the genetic material output from the process is not an exact clone from its parent cells creating genetic diversity. The second is that the outcome of meiosis results in four haploid cells instead of two diploid cells. Meiosis is not considered to be a part of the cell cycle because it is considered to be a one way process to create a new variation of genetic materials, typically for the purpose of producing a new organism for the population.
Stages of Meiosis
Meiosis is divided into two separate stages of the meiosis process. Meiosis I has the same basic processes as mitosis however upon completion the phase of Meiosis II beings.
In prophase I the DNA of homologous chromosomes is exchanged. This is referred to as homologous recombination. The new genome created within the chromosomal crossover is the basis of genetic variation in life forms. New combinations of alleles from this process can result in the divergence of species. Prophase I is broken up into 6 phases of its own.
In the phase of leptotene chromosomes containing sister chromatids condense in the nucleus into strands.
In the phase of zygotene the chromosomes line up with each other into homologous chromosome pairs. Pairing of the chromosomes takes place during this stage.
The stage of pachytene is where chromosomal crossover takes place. The paired up chromosomes from the zygotene phase exchange information during the recombination of non sister chromatids.
During the diplotene stage the homologous chromosomes separate from each other and being to uncoil slightly. In the uncoiling process the DNA transcription occurs which begins the birth of a new lif form.
In the phase of diakinesis chromosomes condense further and intertwine with each other to begin forming the chiasmata.
In the synchronous process the centrosomes being migration to the poles of the cell which function as the organization center of the new cells. Microtubules enter the nucleic membrane and begin separating genetic material.
In the metaphase the homologous pairs converge into kinetochore microtubules and attach themselves to the centrioles on both poles.
During the anaphase stage of meiosis the bipolar microtubules being shortening pulling the chromosomes to opposing sides of the cell. This forms two haploid cells with a recombination of genetic materials. The cell membrane expands and begins to elongate for the process of division.
When the chromosomes reach the centrosomes at the poles of the cell, the meiotic process effectively ends. From here on out division occurs through the process of Meiosis II. Microtubules disintegrate and a new nuclear membrane forms around each haploid set.
Meiosis II is the same basic process as meiosis I however this is the area in which genetic recombination occurs. During this stage the haploid cells swap genetic material to create a new genome for the daughter cells.