What is Meiosis?

As an important component in the process of sexual reproduction, meiosis is the means by which one cell divides into four different cells. Here are some details on the process of meiosis and why meiosis is necessary in order to ensure reproduction..   Meiosis takes its name from the Greek word meioun, which is translated to mean to make something smaller. In effect, that is what happens when meiosis occurs. A diploid eukaryotic cell will begin a process of dividing into four more or less equal portions, referred to as haploid cells. Generally referred to as gametes, the number of chromosomes contained in each of the gametes created from diploids is reduced from the parent diploid cell. Chromosomes contain the basic DNA chain that will determine the physical characteristics of the child in the event that a pregnancy takes place.   During the process of meiosis, the genome of the diploids begins to undergo two distinct rounds of division that ultimately result in the four haploid cells. Each of the haploid cells or gametes will contain one fully complete strand of chromosomes, which equates to half of the chromosomes supplied by the previous division. The gametes are capable of meshing or fusing with other opposite gender haploid cells during the process of fertilization. If the fertilization is successful, this leads to the creation of a zygote. This is important to note, as the union of these two different gender diploids will contained the DNA strands of both of the haploid cells, resulting in a unique physiological makeup for the new life.   The need for a combination of two haploid cells to form the zygote is one of the characteristics that set the process of meiosis apart from other means of reproduction, such as mitosis. While both meiosis and mitosis will rely on some of the same mechanisms to aid in chromatin distribution, it is important to remember that mitosis occurs as a form of asexual reproduction, meaning there is no need for a combination of opposite gender gametes. Meiosis sets the stage for sexual reproduction that results in genetic variations that are based on the unique composition of the two opposite gametes, rather than the creation of new life from a single source.   While there is ongoing research to determine if there is some way to manipulate the process of meiosis, modern science still has a long way to go. At present there are no effective methods to potentially prevent the formation of birth defects, or even create the possibility of altering the basic DNA. This means that modern science does not currently offer a means to produce a desired physical aspect. Until much more is understood about the basic cell structures that divide and change during meiosis, how chromatin is produced, what can create an unhealthy gamete and other related matters, science will have to be content with observing the process as it now stands.     Mitosis is the scientific term for nuclear cell division, where the nucleus of the cell divides, resulting in two sets of identical chromosomes. Mitosis is accompanied by cytokinesis in which the end result is two completely separate cells called daughter cells. There are four phases of mitosis: prophase, metaphase, anaphase and telophase. The first phase of mitosis is prophase. In this phase the chromosomes which are normally spread throughout the nucleus begin to condense into a tight ball. The DNA molecules of the chromosomes begin to interact with enzymes and proteins that assist in the replication of the genes. The compact coiling of the chromosomes at this stage of mitosis is called mitotic chromosomes. Nearing the end of prophase, the material enclosing the nucleus and the cytoskeleton disappears. The cytoskeleton is transformed into what is called a spindle apparatus which works to pull the duplicated chromosomes apart during the anaphase. The second phase of mitosis is metaphase. In this phase the chromosomes of the dividing cell begin to line up and are coordinated with the spindle apparatus. The soon to be divided chromosomes are symmetrically positioned on the metaphase plate typically at the equator of the parent cell. Anaphase is the third step of mitosis. Abruptly the spindle apparatus pulls the two identical sets of chromosomes apart from one another. Each new set of chromosomes is moved to opposite spindle poles. These two sets of chromosomes will soon develop into the nuclei of two daughter cells perfectly identical to each other as well as identical to the parent cell. The final stage of mitosis is telophase which means end.. Telophase is best described as the opposite of prophase. As the chromosomes begin to move toward the spindle pole they start to uncoil and spread out. Then the spindle apparatus made of the former cytoskeleton is deconstructed. Finally the nuclear envelope or membrane is formed around the chromosomes. Although this is the last phase of mitosis, telophase will not be complete until cytokinesis has been carried out. Cytokinesis is similar to mitosis except it involves the cell's cytoplasm and organelles where mitosis is the division of the nucleus or control center of the cell. Once mitosis and cytokinesis are properly completed there are two new functioning cells.