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Down syndrome or Down's syndrome, [12] also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. [3] It is usually associated with developmental delays, mild to moderate intellectual disability , and characteristic physical features.
Charts based on a specific race or ethnicity are not useful because of the growth chart progression can be attributed to socioeconomic factors. [14] WHO launched a revised growth in 2006 chart using children from Ghana, Oman, Norway, Brazil, India and the USA that substantiated the fact that growth is highly dependent on environmental factors.
An anaphase lag of a chromosome 21 in a Down syndrome embryo leads to a fraction of euploid cells (2n cells), phenomenon described as "aneuploidy rescue". There is considerable variability in the fraction of cells with trisomy 21, both as a whole and tissue-by-tissue. This is the cause of 1–2% of the observed Down syndromes. [4]
Down Syndrome Risk Factors Advanced maternal age is thought to be the greatest risk factor for Down syndrome, as a mother's eggs, when older, have more chance of chromosomal abnormalities.
The exact characteristics of Down syndrome were not observed, so more genes involved for Down syndrome phenotypes have to be located elsewhere. Reeves et al., using 250 clones of chromosome-21 and specific gene markers, were able to map the gene in mutated bacteria. The testing had 99.7% coverage of the gene with 99.9995% accuracy due to ...
The Ts1Cje mouse model of Down Syndrome was developed at the University of California, San Francisco in 1997. This model has a partial triplication of MMU 16 that is smaller than the triplicated region in the Ts65Dn model. Ts1Cje triplication contains what has been identified as the Down Syndrome Critical Region, a region involved in all forms ...
“In the most common type of Down syndrome, there are 47 chromosomes, with the extra one being chromosome 21 — so the patient has three No. 21 chromosomes in all the cells of their body. In ...
An 8-year-old boy with Down syndrome became a hero after he alerted his 14-year-old sister of a fire in their Colorado home, helping them get out on time before it was engulfed in flames ...