In the case of Down syndrome
All human beings are made up of cells. These cells possess in their central part a set of tiny structures that determine the characteristics of each, such as hair color, skin color, height etc..
Such structures are called chromosomes.
The number of chromosomes in cells of a person is 46 (23 from the father and 23 from the mother), and these are arranged in pairs, forming 23 pairs.
In the case of Down syndrome, an error occurs in the distribution and, instead of 46 47 cells receive chromosomes. The extra element is attached to the pair number 21 Hence also the name Trilogy 21.
It was first identified by French geneticist Jerome Jejune in 1958.
Dr. Jejune dedicated his life to genetic research to improve the quality of life of patients of Trilogy 21.
3 There types of trilogy 21, detected by a test called a cerotype.
Trilogy 21 simple (or default): the person has 47 chromosomes in every cell (occurs in 95% of cases of Down syndrome). Mosaic: the genetic alteration undertakes only part of the cells, i.e., some cells have 47 and other 46 chromosomes (2% of cases of Down syndrome).
Translocation: the extra chromosome pair 21 is "stuck" in another chromosome. In this case though individual has 46 chromosomes, it is a carrier of Down syndrome (about 3% of cases of Down syndrome).
Still do not know the cause of this genetic alteration, it is known that there is no responsibility of the parent's for it to occur. It is also known that problems occurring during pregnancy as strong emotions, falls, use of medications or drugs are not causing the syndrome, since it is already present as early as the union of sperm (cell of the father) and egg (cell mother).
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