Mitosis, Meiosis and Mendelian Genetics Theory

The term ‘cell division’ refers to the process where two daughter cells are formed from the separation of a single cell. It involves nuclear division, which is referred to as mitosis, and cytokinesis, which is also referred to as cytoplasmic division. Cell division occurs in both reproduction and growth processes (Alberts et al, 2002).

Mitosis is actually the replication of cells. It involves formation of two identical cells from the parent cell. Mitosis occurs in growth and is also very useful in repairing the damaged or aging tissues in the body. It involves division of the nucleus as a part of cell division and occurs only in somatic cells. The chromosome number in mitosis remains the same. It involves all the orgasms, and the products are genetically identical to the parent. The homologous chromosomes do not pair (Henig, 2009).

Meiosis, on the other hand, involves sexual reproduction and results to the formation of four-gamete cell from the main cell. Meiosis results to the reduction by half of the chromosomes. Homologous chromosomes pair during the two divisions and the end results are four daughter cells. It leads to the formation of only sex cells. In meiosis, half of the chromosomes are compliment, and meiosis occurs in sexual reproduction.

Gregor Mendel describes the process of mitosis and meiosis through his principles of inheritance that are responsible for genetic trait transmission. Mendel did not know about chromosomes, meiosis process or genes. He describes genes as paired factors that are inherited independently. Mendel had two laws which are the law of segregation, where only a single characteristic was researched at a time, and the law of independent assortment, where he did research on two characteristics at a time (Morgan, 2007). His law of segregation states that every single characteristic is influenced by two factors. His second law, on the other hand, states that independent inheritance of factors that cause diverse characteristics.

Mitosis occurs in different stages which are divided into two main phases. The first phase is the intrekinesis, or the interphase. In this phase, the cell is not dividing. The second phase is the mitotic phase that involves the cell nucleus division and the cytoplasm division. The interphase stage is generally not regarded as part of the mitotic cell division process (Miko, 2008). This is because cells do not divide at this stage. During interphase, cells are very active. It is at this stage that deoxyribonucleic acid (DNA) is synthesized. This ensures that the new formed cells will have the identical contents of the original.

The first stage of actual mitotic division starts with the shortening of chromatin fibers. They form chromosomes that can be viewed under the light microscope. The chromosomes are made up of identical chromatids that are double stranded. The nucleus disappears at this stage, and the mitotic spindle develops from the centrosomes. The centrosomes are then pushed to the extreme ends of the cell with the extension of the microtubules (Alberts et al, 2002). The spindle is then observed to pull out to the extreme poles of the cell.

The second stage is the metaphase. It is mainly identified by the presence of the metaphase plate. The centromeres of the pairs of chromatids align themselves along the microtubules. This occurs at the central area of the mitotic spindle.

The third stage is the anaphase. This stage involves the separation of the chromatid pair to form chromosomes through the splitting of centromeres. The chromosomes appear ‘V’ shaped when they are pulled by the microtubules since their centromeres move ahead while the trailing arms follow. 

The fourth and the last stage of mitosis is the telophase. The chromosomal movement comes to a halt before the commencement of the telophase. The identical pair of chromosomes located at the opposite poles uncoils to form a tread like chromatin structure. All the chromatin mass then gets a fresh nuclear envelope (Miko, 2008). This is followed by the nuclei appearing and the breaking up of the mitotic spindle. The final transformation in this stage is the division of the cytoplasm around the formed nuclei.

In a simple inheritance, meiosis is used to preserve the number of chromosomes in a species. This occurs where meiosis produces four varied gametes genetically. The gametes originate from a diploid cell, which contains chromosome pairs in full sets. The chromosome pairs have dissimilar alleles of genes and are thus homologous but not identical. The replication of chromosomes is a major factor of maintaining the same number of chromosomes. Meiosis occurs in two phases of division, where homologous chromosomes are separated in the first round. Sister chromatids are then separated in meiosis II resulting to the formation of four haploid cells (Henig, 2009). Each haploid cell contains equal number of chromosomes.

It is essential to note that reproduction and growth includes the processes of meiosis and mitosis. These processes have different stages, each with specific and distinct actions that take place. The cell being the basis of life houses the organelles such as the nucleus and cytoplasm that undergo division. Chromosomes are also very important in inheritance of traits since they carry the DNA which defines the traits of the offspring.