Why do people who have down syndrome all have similar physical appearances?

Question

its pretty obvious when someone has down syndrome because they all have similar faces if that makes sense..but why is this? i know what causes down syndrome, chromosomal wise, but i dont really understand why they look alike

Answer 1

Now that chromosome 21 is sequenced and many of the genes have well understood functionality the likely genes causing the specific defects can be listed. Having an extra copy of all or most of chromosome 21 means the genes on that chromosome are over expressed. Because the developmental process is carefully choreographed for only two copies of every gene any disruption due to additional copies of genes distorts the growing fetus. The surprise is that they survive. Trisomy is lethal with most chromosomes, only 13, 18, & 21 of the autosomes allow a live birth.

The kinase DYRK 1A  (dual specificity tyrosine phosphorylation-regulated kinase) is important in regulating the brains proper growth, too much activity and retardation results.

http://www.lbl.gov/Science-Articles/Arch...

http://www.sciencemag.org/cgi/content/fu...

http://www.pubmedcentral.nih.gov/article...

ETS2 is important in proper construction of cartilage. With an extra dosage of it the skeleton deforms. This gene may be linked to the facial distortions seen and other neural problems.

http://www.nature.com/nature/journal/v37...

http://www.sciencedirect.com/science?_ob...

http://www.tiscali.co.uk/news/newswire.p...

http://www.newsrx.com/newsletters/Cancer...

Answer 2

The mutation causes the same results, essentially, in different people.

Answer 3

genotype determines phenotype

Answer 4

The appearance is caused by the chromosomal defect. Since they all have the same chromosomal defect, they have the same physical defects that are dictated by the genes located on those chromosomes.

Answer 5

it is a symptom of down syndrome. like a symptom of the flu is to have a fever. thats all it is. something from the syndrome makes these things happen.

make it a good day

Answer 6

Please see the link below.