Thursday 29 March 2012

Genetics

Growing Up
Getting Big


The little guy is 18 months old today!! It's hard to believe that it's been that long since we started our new life  learning about what it is to love and raise someone with Down Syndrome. What a beautiful life it has turned out to be.

We have already met so many amazing babies, teenagers and adults with Down Syndrome and their gorgeous families and have learned so much from them. We have made some friendships which will last forever.

Today Felix had his first 'big boy' haircut and is looking less like a baby and more like a little boy. It's sad that his days of being tiny are getting fewer, but we're so looking forward to watching him grow.


Is Down Syndrome Hereditary?


I  have been asked by quite a few people if Down Syndrome is hereditary, so I thought I'd try and explain in a bit more detail about the three different types of Down Syndrome.

Trisomy 21


Karotype
Trisomy 21 is the most common form of Down Syndrome. It occurs in approximately 95% of cases. There is an extra copy of the 21st chromosome present in each cell. You and I only have 2 copies of the 21st chromosome whereas people with Trisomy 21 have 3, hence the name 'Tri'somy 21. That extra chromosome in each cell affects development and it's because of that chromosome that people with Trisomy 21 have distinguishing physical features and some health issues and intellectual delays.

Trisomy 21 is often linked to maternal age, but there are many children with Trisomy 21 born to young mothers. There is also study being done looking at the effect of paternal age on the incidence of children born with Trisomy 21.

Such a happy boy!
This type of Down Syndrome is not hereditary!


A karotype, which is like a photo of your chromosomes, was done when Felix was born. The result was that he has Trisomy 21.

Mosaicism


About 2% of people with Down Syndrome will have Mosaic Down Syndrome or Mosaicism. This is when the extra copy of the 21st chromosome occurs in only some cells in the body. As a result, people with Mosaicism may or may not have the physical characteristics common to people with Down Syndrome. They will be affected physically and developmentally depending on which cells have the extra chromosome.

Like Trisomy 21, Mosaicism is not hereditary!


Translocation


Translocation only occurs in 2-3% of people with Down Syndrome.


Translocation occurs when part of the 21st chromosome attaches itself to another chromosome (commonly number 14). Unlike Trisomy 21 and Mosaicism, Translocation can be hereditary. The person carrying this genetic information will have a much greater chance of having a child with Down Syndrome.

Just Extra Blessed


All of that being said, I know of a couple of families who have been doubly blessed. One of my friends has just had her second child in a row with Trisomy 21. The Doctors have told her that she was one in more than 10,000 people to have had two babies with Trisomy 21. The fact that it is not hereditary means that it was one of those medical miracles that happen from time to time. The funny thing is, she went through a grieving period when she gave birth to her first child and found out he had Down Syndrome, but she was incredibly excited when her second child was born. She knew by then the joy of raising a child with Down Syndrome!

Another lady I was reading about the other day has triplets. One of the three has no disability, but the other two are actually identical twins who both have Down Syndrome. They are about 12 years old now and all very handsome young men. Their family is very active in the Down Syndrome Community.

Loving the beach
An Extra Mention


One of our boys had a friend over yesterday after school. She wanted to come and meet Felix because she has heard the kids talk about him. I was blown away by how beautiful this girl is. During my conversation with her she told me that she has a brother with a very rare Syndrome who is 8 years old. She spoke with such sensitivity and an overwhelming pride and love for her brother. She didn't talk about the things he couldn't do, but all the things he could do. It brought tears to my eyes.

I am so thankful for our kids and for other gorgeous kids like this who are proud to tell people about their siblings, who may have a disability, but at the end of the day are their family who they love and respect.


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