Tuesday, January 24, 2012

A Biology Lesson

Today I went and met with the genetic counselor Maggie. We met with her right after we got our diagnosis and she was able to give us a little information then, but I emailed her the results of the chromosome test and set the appointment to meet with her again. She is such a wonderful caring individual. I went in not knowing what questions I should be asking, what information I should be seeking, and unsure of how much she'd be able to tell me.

For all you scientists out there...

In all Gabriel's tests he had an extra Y chromosome in the 23rd set of chromosomes - XYY. This much we knew when we read the results. Our doctor had filled us in on that. But the thing is, there are many people out there wondering the world with an extra Y chromosome.

Everybody has 23 chromosomes, each set as 2 - an X and a Y. Inside each chromosome are genetic codes (the lines in the chromosome itself). The genetic codes make up who we are (eye color, hair color, etc etc)  This would be Gabriel's chromosome chart - the 23rd chromosome has 2 Ys.

Where does the extra "Y" come from? 
Boys with XYY chromosomes have an additional Y chromosome from their father. In the majority of cases, the two Y chromosomes failed to separate during the formation of the sperm. This is not hereditary - its just a fluke, a malformation in a single sperm cell.   An extra Y chromosome cannot come from a female because we only carry X chromosomes (If it had been XXY it would have been an issue with my egg...).

Thousands of people have an extra Y - few of them end up with Potter's syndrome.
There are thousands of people wondering around with an extra Y chromosome, 1 in 1000 births.  Most never even know they have the extra chromosome. People with an extra Y Chromosome have a normal appearance but are often tall, there is no significant increase in medical problems or illnesses. They are generally average for intelligence but may need assistance in learning and school. There's usually no problems with puberty but may be some behaviour problems and increased vulnerability to stress. Overall they live normal long healthy lives but  a few end up with Potters Syndrome.

Not all Potters Syndrome babies have an extra Y chromosome
Only a portion of Potters babies have an extra Y chromosome. So having the extra Y doesn't CAUSE Potters Syndrome. Somehow Potters Syndrome is associated with the extra Y and the extra Y is associated with Potters Syndrome - but they aren't sure how.

Other possible causes
If both Derrick and I are carrying a recessive gene for Potters Syndrome, and Gabriel happened to get both recessive genes, then its possible its hereditary. She says thats unlikely since we don't have much known kidney problems running in our families. Derrick's cousin does have 1 kidney, but she said that isn't linked because the gene would have to travel through so many generations to get to Gabriel, its nearly impossible to have it travel that far without having signs and symptoms in our families.

So basically, the result is this:  1 in 1000 births have an extra Y chromosome, of those most live perfectly normal long healthy lives while SOME end up with Potter's Syndrome, but not all Potter's Syndrome cases have the extra Y chromosome... Confusing? YES!

She said that unfortunetly with genetics there are no guarantees, they can't say 100% on anything. But this seems to be a common occurance in our situation - so we're getting used to it... unfortunately. They couldn't tell us anything for sure during the pregnancy or after the birth. Now they can't say for sure that Gabriel's condition was caused by the extra Y chromosome (although this is the assumption right now) and they can't say 100% that it wasn't caused from a recessive gene. They can only tell us what they THINK caused it to happen.

She said that because he had the XYY chromosome that was most likely the cause of his Potters Syndrome, if this is the case then our risk is VERY low of reoccurance - (she said in genetics they can't say 0% but its down near there somewhere). If it was hereditary (recessive genes) then it would be 25% reoccurance risk.

Genetic Testing?
A person has THOUSANDS of genes in their make up. Testing for a recessive one in our genes is nearly impossible as they would have no idea where to even start looking. A possibility? Yes, but most likely they would find nothing even if they tried. So not currently a realistic option for us. Although, if we did have another child with Potters Syndrome in the future, if the baby had the extra Y chromosome then we are just very very unlucky. If the child had Potters Syndrome but no extra Y chromosome, then we'd assume it was hereditary and look further into testing. I am going to send her the results from the autopsy so she can show her Genetisist colleague to confirm that there's no further recommended testing.

Sad that we couldn't get more solid answers and explanations of why it happened, but glad that I understand the scientific cause of this condition (even if your beyond confused after reading all of it!). It makes sense in my head, I'm just glad to hear (again) that we have a very low risk of it happening again. And the official end result - unfortunately, I  now know more about genetics and chromosomes than I ever imagined or thought I would - and wish it wasn't because of this that I finally have a semi-understanding of these things.

No comments:

Post a Comment