Genetics- Down’s Syndrome (Trisomy 21)
I’m doing notecards for the diseases I need to know for the first exam in genetics, and the one that had the most detail in it was the one for Down’s Syndrome, trisomy 21. So, I figured I’d share some knowledge.
We all know (or should know) that we normally have 46 chromosomes altogether…46 XX if female, 46 XY if male. Every now and then, however, problems will arise. One of those problems is trisomy 21, which is 3 copies of chromosome 21. The incidence of a female having a child with this disorder increases after the ripe age of 35. It is the single most common cause of mental retardation, with 1 out of 800 newborns being affected. Below I have included a few symptoms and pictures.
*short stature
*simian crease in palm (single transverse line)

*mental retardation
*delayed language development
*flat face with upward slant of the eyes

*clinodactyly- curving of the 5th (little) finger towards the 4th (ring) finger

*low set ears
*large tongue (macroglossia)
*hearing, eye, and skeletal problems
*dementia
Also, it is important to note that there is a protein found on chromosome 21, the beta amyloid precursor protein, that is also found in people afflicted with Alzheimer’s. Needless to say, people with trisomy 21 have a higher chance of also developing Alzheimer’s.


























