21st Chromosome info at Museum of Science and Industry

I find it funny how excited we get...


when we see something about Down syndrome.

We went to the Museum of Science and Industry today.

It's a great museum. We all had fun.


(My niece Karli (who now lives in our basement) was really excited!)

The change in me, and the love I have for my kids
strikes me at odd times.

The fact that I struggled so much at first with Polly's diagnosis
of Down syndrome
with time has become the vehicle that produces overwhelming joy.

If there wasn't darkness, I would not be able to appreciate the vast contrast of light.

(This saying was painting on a wall at the museum.)


"I have learned to love the darkness of sorrow, for it is there I see the brightness of God's face." - Madame Guyon

Different types of Down syndrome?

First question: "Can you tell me the differences between all 3 (I hope that is right) types of Down Syndrome? I get a little confused on the differences. Thanks so much!"

Thanks for asking, Molette!

Yes, there are three types of Down syndrome:

Trisomy 21, Translocation and Mosiac.

Here's an explanation of the three types from the National Down syndrome Society:

Down syndrome is usually caused by an error in cell division called "nondisjunction." Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate. As the embryo develops, the extra chromosome is replicated in every cell of the body. This type of Down syndrome, which accounts for 95% of cases, is called Trisomy 21.

The two other types of Down syndrome are called mosaicism and translocation. Mosaicism occurs when nondisjunction of chromosome 21 takes place in one-but not all-of the initial cell divisions after fertilization. When this occurs, there is a mixture of two types of cells, some containing the usual 46 chromosomes and others containing 47. Those cells with 47 chromosomes contain an extra chromosome 21. Mosaicism accounts for about 1% of all cases of Down syndrome. Research has indicated that individuals with mosaic Down syndrome may have fewer characteristics of Down syndrome than those with other types of Down syndrome. However, broad generalizations are not possible due to the wide range of abilities people with Down syndrome possess.

Translocation accounts for about 4% of all cases of Down syndrome. In translocation, part of chromosome 21 breaks off during cell division and attaches to another chromosome, typically chromosome 14. While the total number of chromosomes in the cells remain 46, the presence of an extra part of chromosome 21 causes the characteristics of Down syndrome.

Keep the questions coming friends! Thanks!