Most people get injuries, which are complex or simple like bruises and, over time, these injuries heal. This healing process may be done through cell division in which a single cell divides to form two or more cells and the process continues like a cycle. This process helps living things grow, for example, more than 2 trillion cells divide each day in humans. There are two types of cell division processes, mitosis and meiosis, each with different characteristics.
A single cell divides into two genetically similar cells. The process is asexual and the resulting cells have the same number of chromosomes in each diploid cell, each with the same nucleus.
Meiosis is the process of sexual cell reproduction in which one cell divides its homologous chromosomes equally to form two haploid cells with half the number of stem cell chromosomes.
Mitosis occurs in five phases that detail the changes through which the cells go. These stages are prophase, prometaphase, metaphase, anaphase, and telophase.
In prophase, chromosomes dissolve in the nucleus while centrioles move in pairs to opposite sides in the nucleus. As this process continues, the spindle fibers begin to form bridges from one end of the cell to the other.
In the next phase, prometaphase, the nucleus that envelops the chromosome begins to rupture and, now without a nucleus, the sister chromatid becomes independent. Long protein chains form the entire cell and are attached to the kinetochore (protein) which is in the center (centromere).
In the third phase, metaphase, kinetochore microtubules induce and attract sister chromatids. The chromosomes are then united in preparation for division.
In anaphase, the two chromatid sisters divide and move toward the cell pole. Although the kinetochore holding the fixed microtubules is attached to the centromere, it begins to shorten in length, while the second group of microtubules not attached to the kinetochore begins to lengthen. The whole cell then begins to stretch and pull in the opposite direction.
Finally, the process enters the telophase stage where each identical chromosome reaches the end pole of the cell while the spindle fibers begin to disappear. On each chromosome, the nuclear membrane forms and forms the nucleolus within each nucleus.
Although not considered part of the mitotic phase, the final process in mitosis is cytokinesis in which cells physically divide before the process begins again.
Meiosis produces two different cells with half the number of chromosomes compared to the stem cell thus increasing genetic variation. There are two main steps of meiosis; meiosis I and meiosis II. The process of meiosis is important because it reduces the number of chromosomes in an egg or sperm to one set and also allows for the propagation of more than one pair of parental chromosomes.
Meiosis I has four phases. In the first phase, prophase I, chromosomes appear, the nuclear membrane disappears, and centrioles begin to build spindle fibers to cover the chromosomes. The chromosome then splits into two sister chromatids whose centromere is held together. Thus, this process means that there are two sets of sister chromatids (four chromatids) in two chromosomes. Two non -cat chromosomes cross because the other two remain. Second, in metaphase I, chromosomes line up in the center of the paired spindle fibers. The third phase, Anaphase I, creatures when the same number of chromosomes are divided. In the final phase, telophase I, daughter cells completely divide, chromosomes disappear, and a nuclear membrane is formed.
Meiosis II also has four phases in meiosis I. First in prophase II, centrioles form spindle fibers as the nuclear membrane disappears and chromosomes become more visible entering into metaphase II where chromosomes are again united in the middle along the spindle fibers. In anaphase II, the chromosome divides into two chromatids that each contain a piece of DNA then the cell divides. Finally, the shape of the nucleic membrane produces four new cells each with different DNA. In men, four cells form sperm while in women, only one cell becomes an egg and the remaining three are reabsorbed into the body.
Summary of Differences
Meiosis occurs in humans, animals, plants, and fungi to produce new genes after a homologous pair. The process of meiosis includes two parts that produce four haploid cells. This process only produces sex cells. Mitosis occurs in all organisms to produce all cells except sex cells. In mitosis, homologues are not paired and division occurs only once to produce 2 identical cells.