In reality, cells in the human body can use two types of division to maintain the constancy of the internal environment and renew tissues. In particular, somatic cells use mitosis, which is extremely similar to cell cloning: a division from one parental cell results in two identical daughter cells with the same set of chromosomes and functionality (Mitosis Versus Meiosis). On the other hand, gametes can be formed from meiosis, when four haploid cells are formed from one diploid cell at once.
When chromosomes divide, it is possible for a daughter cell to have more or fewer chromosomes than nature intended. For example, a healthy person’s somatic cells have 46 chromosomes, but when chromosome pairs diverge — nondisjunction: when a chromosome pair does not separate and diverge into new cells — a cell may have either 47 or 45 chromosomes. A decrease in the number of chromosome pairs by one is called monosomy (2n-1), and an increase by one is called trisomy (2n+1).
Both pathologies are united by the common term aneuploidy, which describes deviations in the karyotype of a diploid organism in which the number of chromosomes is not a multiple of the haploid set. Thus, when chromosomes diverge during cell division, a dysfunction is possible, resulting in a daughter cell with one more chromosome (trisomy) and one less (monosomy).
Several life-compatible aneuploidies are characteristic of the human species. Perhaps the best known of these is Down syndrome, which results in trisomy in the 21st pair of chromosomes. Notably, with this condition, patients’ appearances take on a number of similar features: epicanthus, a flat face with an open mouth, a small nose, and an enlarged tongue. In addition to appearance, Down syndrome also affects the individual’s cognitive abilities: the patient has physical and mental dystrophy (Down Syndrome).
Further, trisomy in the 18th chromosome pair is the cause of a much more deadly disease, Edwards syndrome. In the case of monosomy on the sex X chromosome (23rd pair), the patient develops Turner syndrome. In males, trisomy is also possible, resulting in the 23rd chromosome pair becoming, for example, XXY: this is Klinefelter’s syndrome. Often such conditions can be triggered by aneugens: environmental factors that stimulate the development of aneuploidy. Examples of such aneugens are vinblastine, griseofulvin, colcemid, and mitomycin C..
Work Cited
“Down Syndrome.” MayoClinic. 2018. Web.
“Mitosis Versus Meiosis.” YG, 2017. Web.