eli5 Why does down syndrome cause an almost identical face structure no matter the parents genes?

468 views

Just curious

In: 23486

7 Answers

Anonymous 0 Comments

You’re assembling tables but each kit comes with one and a half set of certain parts. Instead of 4 legs, you get 6 along with all the mounting hardware. With your boss breathing behind your back, you can’t exactly throw away the excess parts.

Most assemblers, when given the extra material will end up putting the extra legs in the middle of the table on opposite sides. The appearance of the tables is different from intended but consistent among all the tables with 6 legs.

This is how Down’s syndrome causes similar physical appearances. Humans typically have 2 of each chromosome, one per parent. People with Down’s syndrome have an extra 3rd 21st chromosome. This causes their cells to express those genes 1.5 times the normal amount. The genes written on that chromosome have many effects on the body and having more of them will affect the body in similar ways among people with Down’s Syndrome.

The 1.5x production of genes on chromosome 21 causes similar physical appearances among people with Down’s syndrome.

Anonymous 0 Comments

Have you ever inflated a rubber glove? With just a little air the glove looks like a hand, but the more air you add, the more it distorts as the palm fills but the fingers don’t.

Down syndrome happens when a person has an extra chromosome. Everyone has two of every chromosome, which means two copies of every gene. Someone with down syndrome has three copies of a small set of genes; the third copy is on that extra chromosome. As a result, those genes get expressed too much, resulting in the familiar features that seem to hide or overshadow the features that would make them more “normal”. We all have these features, but in most of us they’re toned way down. Their gloves have more air in them than ours.

Edit: Many of you have correctly pointed out that DS people do not “all look the same”. They have similar features explained by genetics, yes, but so do various ethnicities. Unfamiliarity can make it difficult for an “outsider” to tell the differences between individuals, but those differences are not only there, they are as stark as the differences between two random French people, or two random Han people.

Anonymous 0 Comments

Since we’re here, can anyone explain why Chromosome 21 is particularly likely to show up ‘with company’? I’ve heard of Trisomy 23 as a layperson, and both XYY and XXY, but that’s about it.

Anonymous 0 Comments

Ok, let me ask this please. I have a client that has facial features of DS but that’s it. Talking with him on the phone I would never know. Even in person when I look at him I have to make special effort to realize that he is not challenged in any way. I think to myself that it must suck to make people realize he has no mental challenges. Am I missing something? Can you have the physical characteristics but but the mental characteristics?

Anonymous 0 Comments

My brother has down syndrome and aside from some of the Down syndrome features, if you compare my mothers pictures as a baby and child to his, they’re practically twins. They do look like their parents, you just don’t see it.

Anonymous 0 Comments

[removed]

Anonymous 0 Comments

[removed]