Genetic testing

I'm not sure if this is the right section to post this but I thought some of the girls doing IVF/PGD might now a bit about genetic testing.

My baby had a very short life due to a genetic condition we didnt know about until she was 3 weeks old. There are various tests happening which we are waiting on, one of which will take 6 months. Does anyone have any experience with Array CGH testing? I cant seem to find a very good definition of it. We havent been tested yet, just our baby.

And if they find something, is there then a long delay to get my husband and I tested? It is really hard not being able to plan my future and everything hinges on these test results!

TIA

The aim of array CGH testing is to identify if a person (your bub) has extra DNA or is missing bits of DNA.

Small deletions (missing bits) or insertions (extra bits) can cause issues if they happen in important bits of DNA. When they (the dr or scientists) are not sure where to look, array CGH testing can help because it looks all over the genome (all the DNA combined).

The way its done is on a 'chip' that has lots of little wells each containing a known bit of DNA from all over the genome. (if you think of the genome like a book, then the chip has all little sentences separated out from the book pasted onto it)

They then get DNA from your bub and add a dye that shows up green.

They have DNA from a control (a person with average DNA) and add a dye that shows up red.

They combine the two lots of DNA and then add this on to the 'chip' with chemicals that allow the DNA to bind to the chip well if the DNA matches the DNA sequence in the chip (so if the exact sentence in the sample DNA matches the sentence in the well).

When they look at the 'chip' under special light they can see green where your bub's dNA has matched the DNA in the well, and red where the control DNA matches.

Where your baby s DNA is 'normal', there will be equal amounts of red & green dye seen. If your bub has a missing section of DNA (a sentence or paragraph or chapter in the book missing), then only the control DNA will bind and so you will see red only. If your bub has extra DNA (has a sentence or paragraph or chapter written in the book twice or more) then you will see more green than red.

By looking at sections from all over the genome (book), then they can see which gene or chromosome (sentence or chapter) may be missing DNA or have extra DNA.

Array CGH can give a diagnosis, or it may help the doctors know where to look next to find a diagnosis.

This technique is not that easy to understand, or explain, but it can be very powerful. especially if they don't have a definitive diagnosis yet.

hope that helps

take care

Kate

Thanks Kate for the explanation. It sounds very technical and complicated. This genetics stuff really facinates me - how they can see so much in something so small even with the microscopes. Its amazing. I wonder if DH and I will be tested as well down the track. Guess I have to wait and see.

If they find a difference in your baby s DNA (a missing bit or extra bit), they may check your DNA and your partner's to see if either of you also have it. If you or your DH have the same change, it might mean that it is just a variation that doesn't cause disease. If neither of you have it, it might mean that the change happened only when your baby was made (in the egg or sperm or when they got together), and this might be why she got sick.

Genetics knowledge has come so far, but there is still so much that isn't known as well.