Meiosis is a process of cell division through which the chromosome number is reduced by half and as a result, producing four haploid gametes or sex cells. These are mature male and female germ cells that are able to sexually unite with the opposite sex to produce zygote. All the haploid cells produced are clearly genetically different from the original mother cell. The distinction occurs due to random distribution of pairs of both maternal that is the egg and paternal sperm chromosomes known as homologous. Meiosis occurs in every sexually producing single-celled and multicellular eukaryote which includes plants animals and fungi. Crossing over on the other hand is whereby homologous chromosomes pair up to exchange egg cells of their genetic material resulting into a recombinant chromosome. Meiosis occurs in eight stages as discussed below.
First and foremost stage of Meiosis is the prophase (I). It’s the longest stage of meiosis, it’s where the duplicated homologous chromosomes condense, coil up, shorten and thicken in pairs and allow for crossing over of genetic segments. This is followed by the metaphase (I) where the bivalent chromosomes move to the metaphase plate an equidistant plane from the pole of the meiotic spindle.
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The third stage is the anaphase (I). The bivalent chromosomes separate with the sister chromatids attached at the centromere and move in a direction towards the opposite poles of the spindle. After the pole ward movement, then comes the telophase; each pole has a pair of complete haploid of chromosomes. A cleavage appears and cytokinesis which is the cytoplasmic division of the two daughter cells takes place.
Prophase (II) stage follows, in this stage, meiosis (II) begins with the two daughter cells of the meiotic division in the telophase. A new spindle forms around the chromosomes and the nuclear envelopes break. The chromosomes are arranged in a fully formed spindle in the diagonal center of the metaphase plate.
Lastly, the two last stages that complete the process of meiosis are the anaphase two and the telophase two. In the anaphase (II), the centromere of the daughter chromosomes divide or separate and the chromatids move to the opposite poles of the egg cell while in the telophase (II), a nuclear envelope forms around the set of chromosomes and the cytoplasm breaks. This process goes in a repetitive circle as asserted by Simon, Reece and Dickey (2010).
It should be clearly noted that there is difference between meiosis and mitosis as much as they are all associated with cytokinesis. Meiosis has two phases of genetic separation and cellular cell breakage while mitosis only experiences one phase of genetic separation and cellular breakage and that the two daughter cells in meiosis are not identical while in mitosis they are identical to genetic parents.
References
Simon, E. J., Reece, J. B., & Dickey, J. (2010). Campbell essential biology with physiology . Benjamin Cummings.
