Chromosomal pathology can occur due to a violation of the divergence of the entire set of chromosomes in meiosis. Gametes are formed with an unreduced number of chromosomes, which have not one set of chromosomes, but two. When this egg is fertilized with gametes with a haploid or diploid set of chromosomes, polyploid zygotes are formed. Polyploid organisms usually have gross malformations and die in the early embryonic period. There may be a violation of the divergence of individual chromosomes in the set; gametes are formed in which there is no or extra chromosome. Therefore, the zygote that occurs during fertilization is characterized by mono-, tri- or tetrasomy. Most often, such disorders. Of all the syndromes resulting from autosome nondisjunction, the most common pathology is Down’s disease (95% of the total number of trisomies for autosomes). With Down’s disease, trisomy of the 21st chromosome is observed. Clinical signs of the disease are short stature, a wide round face, closely spaced eyes with narrow eye slits, and a half-open mouth.
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