The Structure of Chromosome and the Influence of Epigenetic Factors

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The Chromosomal Theory of Inheritance, proposed by Walter Sutton and Theodor Boveri in 1902-1903 is considered a landmark in the science of genetics (Martins, 1999). The theory established chromosomes as the carriers of hereditary information (genes). It also implied that chromosomes (and not genes) undergo segregation and independent assortment as proposed by Gregor Johann Medel (1865-1866) in his Laws of Inheritance. A chromosome can contain more than one gene(s). Although the contemporary scholars were highly skeptical of this idea, Thomas Hunt Morgan (1915), showed linear arrangement of genes in chromosomes providing a convincing evidence for Sutton-Boveri’s work. The aim of this essay is to investigate the structure of a chromosome and how external factors such as the environment and epigenetics causes alteration in its structure and therefore its function.
Chromosomes are only visible during the metaphase stage of cell division and are seen as condensed thread-like structures when observed under a microscope. Most of the time they are dispersed in the nucleus of a cell in the form of thin fibers, called chromatin. Chromosomes differ from chromatin due to the fact that they are more highly compact and coiled. Extensive study has been done on the structure of chromosome. (Ris & Kubai, 1970, Weintraub & Van Lente, 1974, Gillies, 1975, Paulson & Laemmli, 1977, Comings, 1978, Howell & Hsu, 1979, Marsden & Laemmli, 1979, Lima-de-Faria, 2003). It can be noted from these studies that chromosome structure varies greatly among viruses, prokaryotes and eukaryotes. Viral chromosomes are made of a nucleic acid surrounded by a protein coat while in prokaryotes they tend to be just a copy of a circular DNA molecule arranged in the nucleoid...

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