Thursday, March 21, 2013

Trisomy Twenty What!?

The science geek in me wants to take today, World Down Syndrome Day, to explain what Trisomy 21 is and how it happens.

To begin, our sex cells (egg & sperm) go through a process called Meiosis. This is how they "reproduce." During meiosis, the number of chromosomes is cut in half (Chromosomes carry our DNA from parent to child.). This happens so a baby gets half its chromosomes from mom and half from dad. An egg cell has 23 chromosomes and a sperm cell has 23 chromosomes. 

Men produce sperm throughout their lifetime. Women are born with all the eggs they will produce. At times, when an egg goes through Meiosis, the chromosomes don't split correctly and an egg will end with 24 chromosomes rather than 23. Some scientists say the eggs are "old," because they have been "alive" for how ever many years the woman has been alive. When this particular egg becomes fertilized by sperm, the embryo will end up with 47 chromosomes. Humans have 46 chromosomes. 

Shortly after the girls were born, I read books and articles about Down Syndrome, to see if I could learn more about it and how to better Lorelei's future. For about the first month, I felt like it was my fault because my eggs were "old." Why!? I was only 27! I just didn't understand. It's truly amazing how the human body works, so why would an egg that was so young not do its job correctly? I now know better, but it took me a while to accept it. 

Back to the science...

These 46 chromosomes are split into 23 pair.

For Down Syndrome to occur, the egg that is fertilized will have 24 chromosomes and the sperm will have 23. There will be 3 chromosomes on #21, hence Trisomy 21.

Just as with anything else, Down Syndrome has a spectrum. Individuals will be affected differently and will all be different from each other. Individuals with DS are not cookie cutter, just as typical individuals are not cookie cutter. It is all a learning process and we are doing it together!

I hope you enjoyed the science lesson! :)

We hope you "Rocked Your Socks" and had a wonderful World Down Syndrome Day!

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