system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do people with Down Syndrome tend to have similar face structures?
gpt
The facial features seen in Down syndrome are due to the extra chromosome (trisomy 21).

They are due to the extra "dose" of the affected gene (trisomy 21).

The effects are that epicanthal folds are produced on the eyes, which are almond shaped. Alongside this, the face trends to be flattened and ears are set low.

As well as these facial features, individuals with trisomy 21 also have short stature and small hands too.

It's the combination of the features together, especially the epicanthal folds of the eyes that are distinguishing.