Genetic Modification And Chromosomes

Genetic modification and chromosomes

Introduction

The process by which the cells originate is called a cell division. According to one of the postulates of cell theory, new cells only originate from other living cells. So that the cell can be divided, the genome must also do so. Millions of bone marrow cells or the digestive tract of the human being are being divided at all times. The production of these cells is of great importance to replenish old or dead cells. Cell division occurs in all organisms and is a different process in eukaryotes and prokaryotes.

Developing

In prokaryotes and eukaryotes, cell division produces two equal daughter cells from a progenitor cell. When an eukaryotic cell is divided asexually the mitosis is carried out. Mitosis serves to create new cells for this to happen, the nucleus and genetic content must also do so. The nuclei of the haploid and diploid cells are mitotically divided. In the mitosis, thanks to the movements of the chromosomes, all the daughter cells carry chromosomes and genes equal to those of the other daughter cell and the progenitor cell.

The cell division cycle consists of four stages: S, DNA S Bullet Synthesis, M, Mitosis, and G1 and G2. In the S stage, the DNA of each semiconutative chromosome is replicated. There is a pair of sister chromatids when the chromosome is divided, and each chromatid contains a replicated DNA molecule. These chromatids can only be microscopically visualized in the mioposis stage.

During the myitosis, the DNA daughters molecules separate the opposite poles of the daughter cell, and that is where two equal nuclei are formed in the daughter cells.

Most eukaryotic organisms also reproduce sexually. The beginning of the sexual cell division is carried out with a diploid cell called meiocyte, these are a subpopulation of reserve cells for cell division. Meiocytes are divided twice into all eukaryotic organisms, these two divisions generate four haploid cells. Meiosis is essential for the production of new organisms with sexual reproduction. In meiosis the chromosomal material is divided once and the cell twice, thus reducing the number of chromosomes, so cells are produced with half of the genetic content of the stem cell.

conclusion

The homologous chromosomes are paired before the First Nuclear Division and thus there are two pairs of sister chromatids juxtaposed for each chromosome, forming a tetrad and in this the pair of sister is produced. These chromatids reciprocally change homologous DNA sections through crosses. These crosses are a source of genotypic diversity, and in the exchange of homologous chromatid.

In the First Division the replication of the centromérico DNA occurs. In the Second Division the centromeres are divided, the use fibers are gathered and a sister chromatida is left in each pole. One of the characteristics of meiosis is that for each cell, the number of chromosomes is reduced by half. Another characteristic is that in the First Division, in the cell the homologous centromeres are taken to the opposite poles by the spindle fibers.

Bibliography

• Griffiths, a., Gelbart, w., Lewontin, r. and Miller, J. (1999). Modern Genetic Analysis. 7th ed. [Book] New York: W. H. Freeman and Company. All Rights Reserved., p.Chap. 4.
• Karp, g. (2005). Cellular and molecular biology. 7th ed. Mexico: McGraw-Hill Inter-American, pages. 572-577.