Meiosis from the Ancient greek is a reductional division) is a division that takes place within a division. It is a type of cell division of germ cells in sexually reproducing organisms that is used to produce gametes, such as sperm or egg cells, and is unique to these organisms. This procedure involves two rounds of division, which results in four cells with only one copy of each chromosome at the end of it (haploid). Aside from that, genetic material from the paternal and maternal copies of each chromosome is crossed over prior to division, resulting in the creation of new combinations of code on each chromosome after division. Later on, during fertilisation, the haploid cells produced by meiosis from both a male and a female will fuse to form a zygote, which is a cell with two copies of each chromosome for the second time in its history.
Definition
Melia (also known as meiosis) is a type of cell division that occurs in sexually reproducing eukaryotes. It results in the formation of four daughter cells (gametes), each of which has half the number of chromosomes as the original diploid parent cell.
In sexual reproduction, haploid cells divide to form gametes, which by joining with another haploid cell during fertilisation define sexual reproduction and the formation of a new generation of diploid organisms.
Phases of meiosis
Meiosis is divided into stages or phases.
Meiosis is divided into two stages: meiosis I and meiosis II, which are further subdivided into Karyokinesis I and Cytokinesis I and Karyokinesis II and Cytokinesis II, and Karyokinesis I and Cytokinesis II, respectively. In terms of pattern and name, the preparatory steps that lead up to meiosis are identical to those that occur during interphase of the mitotic cell cycle. [10] Generally speaking, the interphase is divided into three phases:
In the first phase of cell growth (G1) : the cell synthesises a large number of proteins, including enzymes and structural proteins that will be required for cell growth. This is a very active phase in which the cell produces a large number of proteins. A single linear molecule of DNA constitutes each chromosome in the G1 state.
A cell’s genetic material is replicated during the synthesis (S) phase, which results in each chromosome duplicating to form two identical sister chromatids that are attached at a centromere. Because the number of centromeres in the cell remains constant, this replication has no effect on the ploidy of the cell. In the light microscope, the identical sister chromatids do not yet appear to have condensed into the densely packed chromosomes that are visible. This will occur during the first prophase of meiosis, during prophase I.
Growth 2 (G2) phase: Meiosis does not have the G2 phase that is seen before mitosis. Meiosis does not have the G2 phase that is seen before mitosis. Meiotic prophase is the phase of the cell cycle that is most similar to the G2 phase of the mitotic cell cycle.
Meiosis I occurs first, followed by meiosis II, and then interphase occurs. Meiosis I divides replicated homologous chromosomes, each of which is still composed of two sister chromatids, into two daughter cells, resulting in a halving of the number of chromosomes in the population. The decoupling of sister chromatids occurs during meiosis II, and the resulting daughter chromosomes are separated and segregated into four daughter cells. The daughter cells produced by meiosis are haploid, meaning that they contain only one copy of each chromosome in the case of diploid organisms. Cells in some species enter a resting phase known as interkinesis between meiosis I and meiosis II, which is characterised by a lack of movement.
In Meiosis I and II, the cell cycle is divided into four stages: the prophase, metaphase, anaphase, and telophase. These stages are analogous in purpose to the mitotic cell cycle’s analogous subphases. As a result, meiosis includes the stages of meiosis I (prophase I, metaphase I, anaphase I, telophase I) and meiosis II (prophase II, metaphase II, anaphase II, telophase II) (prophase II, metaphase II, anaphase II, telophase II).