- What happens in the cell cycle with Down syndrome?
- What are the other causes of Down syndrome?
- Who Discovered Down Syndrome?
- References
The syndrome develops an extra copy gene in all or part of chromosome 21. That is, three chromosomes together instead of two, because usually grouped in pairs in the nucleus of the cell.
This is scientifically called trisomy 21, the result of which is Down syndrome. This syndrome is characterized by the presence of a variable degree of learning ability and peculiar physical features that give it a recognizable appearance.
In the image you can see how number 21 has three chromosomes, which results in Down syndrome, while the others have only two chromosomes.
The word cell comes from the Latin: cellula, which means small room. Cells make up life, because they are the structural basis of every living organ or tissue on planet earth.
Humans are multicellular because they have several more complex cell types, also known as eukaryotic cells. In organisms such as bacteria, for example, they are unicellular because they have only one cell, and are known as Prokaryotic cells.
What happens in the cell cycle with Down syndrome?
Chromosomes in human eukaryotic cells are classified by sex. Each cell typically contains 46 chromosomes; They are 23 from the father, called X chromosomes, and 23 inherited from the mother, called Y chromosomes.
Chromosomes come together in 23 pairs. This means that each pair contains an X chromosome and a Y chromosome.
A person without Down syndrome has 46 chromosomes. A person with Down syndrome has 47 chromosomes, because trisomy occurs in the 21st pair, a third chromosome appears. This is the most common form of Down syndrome.
What are the other causes of Down syndrome?
The remaining 5 percent of Down syndrome cases are due to conditions called mosaicism and Robertsonian translocation.
Mosaicism in Down syndrome occurs during or after conception. When cell divisions in the body are normal, while others have trisomy 21.
Another form is the Robertsonian translocation, which occurs when part of chromosome 21 breaks during cell division and attaches to another chromosome, usually chromosome 14.
The presence of this extra part of chromosome 21 causes some features of Down syndrome. Although a person with a translocation may appear physically normal, he or she is at higher risk of producing a child with an extra chromosome 21.
The estimated incidence of Down syndrome worldwide is in the range of 1 in 1,000 to 1,100 newborns.
Who Discovered Down Syndrome?
The English physician John Langdon Haydon Down described in 1866 a certain mental retardation that existed in 10% of his patients, who had similar facial features.
In 1958, almost 100 years after the original description, Jerome Lejeune, a French geneticist, discovered that Down syndrome responded to a chromosomal abnormality.
Down syndrome -or trisomy of chromosome 21- was then the first syndrome of chromosome origin described and is the most frequent cause of identifiable mental retardation of genetic origin.
References
- Cell cycle and cell size regulation in Down syndrome cells. ROSNER, M; KOWALSKA, A; FREILINGER, A and others. Taken from the site: ncbi.nlm.nih.gov/
- World Down Syndrome Day. UNITED NATIONS ORGANIZATION. Taken from site: un.org/es
- Biochemical perspective and understanding of Down syndrome. MONTOYA VILLEGAS, JULIO CÉSAR; SATIZÁBAL SOTO, JOSÉ MARÍA and others. Taken from the site: redalyc.org
- Down's Syndrome. First part: clinical-genetic approach. KAMINKER, PATRICIA Y ARMANDO, ROMINA. Taken from the site: scielo.org.ar/
- What causes Down syndrome? CIRCLE 21. Taken from the site: circle21.com
- Image N1: Gene Silencing For Down Syndrome Prevention Using Stem Cells. Taken from the site: geneyouin.ca/