Down+Syndrome-Genetics

= Genetics of Down Syndrome =

the 3rd chromosome in the 21st set Every human in the world is made of cells, and in every cell there is a nucleus, and in every nucleus there are 23 sets of chromosomes. Usually there are 23 sets of 2 chromosomes, but with the genetic disorder down syndrome in the 21st set of chromosomes has a trisomy so instead of there being 2 chromosomes there are 3. These 3 chromosomes are usually caused by something called cell nondisconjunction, which causes an embryo with 3 copies of the 21st chromosome instead of 2. there are 2 types of down syndrome, mosaicism and translocation. Monosaicism occurs when nondisconjunction occurs in only one of the initial cell divisions. translocation only occurs in about 4% of the downsyndrome cases. Translocation is when the part 21 chromosome breaks off and attaches to another chromosome ttpically chromosome #14.