Comparing Mitosis and Meiosis: Processes and Purposes

M phase of the cell cycle is where most of the reorganisation takes place so that all of the cells components are moved around. As a cell enters M phase it has two possible fates: the first one is to enter mitosis to produce two diploid genetically identical daughter cells, the second one is to enter meiosis to produce four haploid genetically non-identical daughter cells (Cooper, 2000). There are many similarities and differences between the two that will be covered in this essay.

Mitosis is a vital process to ensure the growth and development of an organism and this lasts for about an hour. Mitosis is involved in wound healing and replacing lost cells. Meiosis is a longer process that produces haploid gametes that at fertilisation will combine

In prophase the nuclear envelope breaks down and the nucleolus disintegrates, then the centrosome which is known as the microtubule organising centre, copies itself and these move to opposite poles of the cell and these help to form the mitotic spindle. The chromosomes supercoil and are seen as two identical sister chromatids held together by their centromeres (GENIE, 2010). The next stage prometaphase involves the chromosomes lining up in the middle of the cell on the metaphase plate, the mitotic spindle fibres then bind to the kinetochores of the chromosomes. These are associated with the centromeres on the chromatids (GENIE, 2010). The kinetochore is the centre of the chromosome. The third stage metaphase involves the chromosomes aligning themselves on the metaphase plate ready to enter anaphase. Then anaphase is where the centromeres divide and each sister chromatid is moved to opposite poles of the cell. The spindle fibres are involved in this. They are now referred to as daughter chromosomes. Telophase is the last stage and it’s where the chromosomes relax and nuclear envelopes form around each one, then the spindle fibres break down and the cell divides by cytokinesis. Before cytokinesis though, there is karyokinesis which involves the separation of the genetic material (GENIE, 2010). Cytokinesis is where the cytoplasm divides in two involving a contractile ring

The first sub phase of this is prophase 1 and this is split up into 5 stages. The first one is leptotene and this is where the chromosomes supercoil. The second one is zygotene and this is where the homologous chromosomes form pairs and these are called bivalents. Pachytene is where crossing over occurs between the homologous chromosomes and chiasmata form. Diplotene is where they start to separate but remain attached to each other by the chiasmata. Diakinesis is the last stage and this is where they keep separating and the chiasmata moves to the ends of the chromosome (GENIE, 2010). The second phase is prometaphase and this is where the spindle fibres assemble and the chromosomes become anchored to them by their kinetochores. Metaphase 1 is where the bivalents assort randomly on the metaphase plate. This helps to create genetic diversity. Anaphase 1 is where the bivalents separate and the homologous chromosomes move to opposite poles of the cell. Telophase 1 is where the nuclear envelope reforms after disintegrating in prophase 1. Then cytokinesis is where the cell divides to create two new cells which are haploid (GENIE, 2010). The next main stage is meiosis 2 and this is where each chromosome is split into 2 sister chromatids. Prophase 2 is the first stage and this is where the chromosomes supercoil, the mitotic spindle forms and the nuclear envelope disintegrates. Metaphase 2 is where the chromosomes become attached to the