The initial task of the present paper is to define the concept of meiosis and to outline how DNA is split into gametes. The relation of the process to Mendel’s patterns of inheritance is also relevant and represents interest for the research. However, to study this relation it is first of all necessary to understand what the essence of the process is.
Meiosis is the basic process happening in the cells carrying the genetic information about the organism into two cells, while the number of chromosomes in the resulting cells is divided into two equal parts, thus having half of the necessary genotype and making half of the contribution to the formation of the new organism. Traditionally, meiosis is contrasted to mitosis – a regular cell division of cells, in which the number of chromosomes remains full. The chromosomes are fully replicated and have the sister chromatids that are closely tied to each other, remaining in the same condition further (Alberts et al., 2002).
In contrast, a haploid gamete produced from a diploid cell through meiosis must contain half the original number of chromosomes. It must contain only one chromosome in place of each homologous pair of chromosomes, so it is endowed with either the maternal or the paternal copy of each gene but not both. This requirement makes an extra demand on the machinery for cell division (Alberts et al., 2002).
Meiosis is the process that does not become evident at once – it starts as a mitotic division. First of all, DNA replication happens, producing two sister chromatids and forming a bivalent union with four chromatids. Meiosis has prophase that is long and during which pairing occurs, allowing genetic recombination. Then goes the metaphase during which bivalents are lined up on the spindle, and the finishing meiotic stage is called anaphase – it is the process of separation of sister cells, their location at different poles of the spindle, and the final division of the cell.
However, the process of gametes’ production is much more complex and has certain peculiarities. The most notable one is that for the production of haploid gametes two meiotic divisions are required. The first stage described above results in gametes having “a haploid number of chromosomes but a diploid amount of DNA” (Alberts et al., 2002). Thus, a second cell division happens to duplicate the DNA. As a result, every case of meiosis produces four daughter cells out of one.
Meiosis is the principle of DNA inheritance in all organic beings, be it a plant, an animal, or a person. It suggests the equality of genotype that is transferred by the splitting cell to the resulting daughter cells. However, in the discussion of meiosis, it is very relevant to mention the patterns of inheritance worked out by Gregor Mendel – the biologist who investigated the revelation of genotype in its outer expression – phenotype. During his persistent work, the researcher discovered that despite the common number of chromosomes and the equal amount of DNA contained in them there are dominant and recessive genetic features.
Gregor Mendel observed several generations of different plants and investigated the presence of certain features evident in their phenotype. Through this work he found out that some features are present in all generations, thus being dominant and suppressing other characteristics. Recessive characteristics were those that were not evident in every generation and revealed themselves only once in several generations. However, they were present and did not go away, since the genotype is constant and unchangeable (Miko, 2008).
The two concepts, the one of meiosis and one of patterns of inheritance, directly relate to one another because they both investigate one common feature – the genotype and DNA transfer from one generation to another. However, meiosis deals only with the question of the amount of DNA and the scheme of its transfer, while Gregor Mendel went further and investigated the issues of distribution of genes in their influence on the phenotype.
References
Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., and Walter, P. (2002). Meiosis. Web.
Miko, I. (2008). Gregor Mendel and the principles of inheritance. Nature Education 1(1). Web.