Butschli This presupposes that all the activities that

Butschli suggested in 1876 that cell division comes about as a result of an increase in surface tension, prior to nuclear division, in the equatorial region of the cell. According to him, it is pre-requisite for substances streaming from the centrosomes to peak in concentration in the equatorial plane making it seem like these substances increase the surface tension at the surface of the cell with the most marked increase occurring at the equatorial region. This by his assertion will render the surface tension at the poles lower than at the equator.Today, we know that for Butschli’s assertion of cell division to hold, will mean that there should be streaming of materials towards the equator while the surface of the equator would have to be highly curved with relatively curved edge and equatorial surfaces highly flattened. If this were true, the result of the process would have been the formation of a flattened disc with a highly curved edge with the latter representing what was the equatorial surface of the edge prior to the process. Rather than what would have occurred in Butschli’s description, it is evident that cell division is the production of two spheres from one of approximately twice the volume of each of the two spheres referred to as daughter-cells. The take-home information herein is that cell division is an increase in surface which consequently diminishes surface tension rather than increasing it which was experimentally illustrated by Quincke. In this paper however, significant attention shall be given to the mechanics of cell division and how it influences the cell cycle and programmed cell deathCell is the basic functional unit of life. This presupposes that all the activities that occur at the organismal level is a combined activities of similar cells. As these cellular activities occur, old cells lose their viability and would need to be replaced. The process through which this phenomenon, replacing less viable cells with newer ones, is achieved through cell division which is thrown into predetermined mechanics called phases. It is also worth stating that the growth of a single fertilized egg into a matured organism, replacement of dead tissues and diseases like cancer are all possible through this phenomenon. The cell cycle is made up of an ordered series of macroolucular proceedings that lead to mitosis, formation of two daughter cells. Each one of the formed cells produced containing chromosomes indistinguishable to those of the cell from which it was made alternatively referred to as parental cell. Doubling the parental chromosomes happens during the S phase of the cycle, with one of the produced daughter chromosomes distributed to each daughter cell at the time that the cell wall is splitting (cytokinesis) (see Figure 9-3). In order to ensure that replication of chromosomes and their isolation to daughter cells occur in a predetermined order, and with extremely high fidelity, there is clear-cut temporal control of the events inherent in the cell cycle. It must also be noted that regulation of the cell cycle is pivotal in order to ensure normal development of organisms of multiple cells. This also means that in an event where there is loss of control cancer, a diseases known to in developed world to kill one in every six, ensues. Somewhere In the late 1980s, it was determined that the molecular procedures which regulate the two important events in the cell cycle, chromosome replication and segregation, are basically similar in all nuclei containing cells. This outstanding discovery served as a springboard for research with diverse organisms, with each of these organisms offering its own experimental advantages, in order to contribute the growing understanding of how events in the cell cycle are coordinated and regulated. Several techniques and procedures such as Biochemical and genetic experiments, coupled recombinant DNA technology, have been devised to allow for studies in various aspects of the eukaryotic cell cycle. These studies have made profound discoveries, including that cell replication is primarily checked by regulating the timing of nuclear DNA replication and mitosis. The chief regulators of the events of the eukaryotic cell cycle are a small number of heterodimeric protein kinases that contain a regulatory subunit (cyclin) and catalytic subunit (cyclindependent kinase). These kinases check the events of several proteins involved in DNA replication and mitosis specific regulatory sites phosphorylation. This strategic phosphorylation activate some and/or inhibit varieties of proteins to coordinate their activities. Cell cycle leads to cell replicationAs illustrated in Figure 21-1, The cell cycle is thrown into four distinct and predetermined major phases. In replication of somatic cells, cells make RNAs and proteins during the G1 phase, in waiting for DNA synthesis and chromosome duplication at the S (synthesis) phase. After succeeding through the G2 phase, cells kick starts the rigorous and complex process known as mitosis, also called the M phase or mitotic phase. Even though the mitotic phase is part or the bigger process, cell cycle, it is also in itself divided into several stages (see Figure 20-29). In the discussions of mitosis, it is preferable or common to use the term chromosome to refer to the replicated structures that condense. During the prophase period of mitosis, the condensed chromosome is visible under the light microscope. Accordingly each chromosome is made of the two daughter DNA molecules following DNA replication and the histones as well as other chromosomal proteins that is associated with them (see Figure 10-27). The indistinguishable daughter DNA molecules and associated chromosomal proteins that is at this time seen as one chromosome are denoted as sister chromatids. Sister chromatids are associated to each other by protein cross-links lengthways. In vertebrates, sister chromatids become restricted to a single region of connotation called the centromere while chromosome condensation occurs. Throughout interphase, the portion of the cell cycle sandwiched by the end of one M phase and the start of the next, the outer nuclear membrane becomes continuous with the endoplasmic reticulum (see Figure 5-19). With the onset of mitosis in prophase, the nuclear envelope withdraws into the endoplasmic reticulum in a greater number of cells from higher eukaryotes, and Golgi membranes breakdown down into vesicles. In this moment, the mitotic apparatus is prearranged into a central mitotic spindle and a pair of asters (Figure 20-31a; see also Figure 20-2c). The spindle is a mirror-imaged packet of microtubules together with its associated proteins assuming an overall shape of a football. An aster is a start-shaped of microtubules found at each pole of the spindle. At each half of the spindle is a single centrosome which organizes three different factions of microtubules whose negative ends point at the centrosome (Figure 20-31b). One set forms the aster; they radiate toward the cortex of the cell away from the centrosome to assist in the positioning of the mitotic apparatus in order to determine the division plane during cytokinesis. The other two sets of microtubules is made of the spindle. During metaphase, the kinetochore, gathers at each centromere to allow for kinetochores of sister chromatids to associate with microtubules that originate from opposite spindle poles (see Figure 20-31). Sister chromatids separation occurs at the Anaphase of mitosis. In the initially stages, they are pulled by motor proteins lengthwise the spindle microtubules to the opposite poles and further separated as mitotic spindle lengthens (see Figure 20-40). Mitotic spindle aggregation stops and chromosomes condensation ceases immediately chromosome division is completed during telophase. Nuclear membrane forms around the aggregated chromosomes again as they decondense. Division of the cytoplasm, popularly referred to as cytokinesis, then results in the production of two daughter cells and Golgi complex formation begins in each daughter cell.