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The Lowdown on Twisties: Balanced Translocations 101

I almost don't want to do this. It entertains an awareness of what we are faced with, each time we fall pregnant, that I don't want to confront again (we went through this 3 years ago when we first found out about Steve's balanced translocation and it was horrifying to research, to say the least - we waited just two more pregnancies before we got Ella, though, so it kind of softened the information we found). There are so many variations with reciprocal translocations, and this one is just one kind. The most common, in fact.

After 7 miscarriages to date (between April 2000 and Sept. 2005), two IVF cycles and six years and counting of hoping for another miracle, we can't deny that this balanced translocation business is a tricky, fickle condition that so far hasn't played fair with us. UPDATE

The following is our understanding of sessions with our genetic counsellors and through research on the internet. This is just our take on it and is here merely to add to a wide variety of far more intelligent, medical fact-related information out there!

You may also find the following sites useful for their fantastic diagrams and definitions to help in your search:

Encyclopaedia of Genetic Disorders - Karyotype information.

What is a Translocation? - a very well laid-out and descriptive site, includes diagrams of a Translocation.

The t(11;22)(q23;q11) translocation - The most frequent constitutional translocation in humans
- Oxford Journals Human Molecular Genetics, a fascinating study including diagram showing FISH (Fluorescent In Situ Hybridisation) of chromosomes.

Genetics Lecture: Cytogenetics - The normal human chromosome complement
- another brilliant page full of diagrams and information on how our delicate genes can sometimes undergo structural abberations, including balanced rearrangements such as translocations and inversions, as well as numerical abnormalities like deletion, trisomy, monosomy, aneuploidy, euploidy, etc., along with another explanation of the FISH technique.
Put your thinking cap on for this link!

Unexpectedly high rate of de novo constitutional t(11;22) translocations in sperm from normal males - fascinating communication from Nature Genetics, worth a read if you want a very scientific analysis, including the finding that the translocation potentially occurs during meiosis.

The Canadian based support website Chromosome 22 Central is looking for Australian members. If you are looking for support, a place to share information, or somewhere to feel like you fit in - this could be a good starting point. Despite searching (and being asked over these past few years), we are yet to discover an Aussie-based equivalent community site for similarly affected families. If anyone knows of such a website, please contact us so we can help spread the word!

Steve has a non-Robertsonian reciprocal balanced translocation of chromosomes 11 & 22, with the breaks on the q arm at point 23 on chromosome 11 and point 11 on chromosome 22. You'll see it like this - t(11;22)(q23; q11) - in medical terms. Not only are the two chromosomes pertinent, but where they actually break (and have swapped with each other) are also important. This translocation is the most common in humans. The breaks at those two points (q23;q11) are also the most common. Oh, so what the geneticist was trying to say to us was (say it with me Python fans), "'e's not an individual, 'e's a very norty boy!" The carrier (that would be Steve, in our case) is normal, often not aware of their uniqueness until they try to have offspring or give birth to an unbalanced baby.

What happens is this (and it's so hard without diagrams but let's give it a shot):
Your chromosomes, when lengthened out, are shaped like an X - there is a long arm (p) and a short arm (q). Each arm contains vital genetic information. Each of these genes, spaced along each arm (and there are thousands upon thousands of genes), determines certain patterns or outcomes. For instance, there's genes for eye colour, there are about 100 that relate to the makeup of the heart and how it's going to form, there are genes for every single thing that make up YOU. That's why we're all so unique. Awww. Back on the chromosomes themselves, the lower the chromosome number, the larger the physical chromosome is. So, chromosome 1 is one of the largest in size, while chromosome 23 is a little itty bitty thing. From my understanding, the larger the chromosome with a 'problem', the greater you could expect the defect. In other words, a chromosome 2:7 translocation or similar would have far more life threatening defects. Er.... not that our list isn't impressive.

Now, in two of these chromosomes, in someone with a translocation, a break has occurred. Imagine two sets of Twisties side by side, each set containing one big Twistie and one slightly less so. One set (chromosome 11) is a cheese Twistie and the other (22) is a chicken Twistie. Still with me?

Now.... snap off the bottom 5mm from the long arm of the chicken and the long arm of the cheese Twistie. Then tack the resulting piece of the chicken Twistie onto the bottom of the cheese Twistie (where its piece has broken off). Do the same in reverse: put the broken off piece of the cheese one onto the chicken Twistie's long arm.

And what you get is a balanced translocation. Ta-da! Now you have a little piece of cheese (11) on the chicken Twistie (chromosome 22) and vice versa. This Twistie arrangement is all good for Steve; he still gets his two full Twisties and doesn't miss out on a thing. Medically speaking, he has no missing genetic information and is (obviously) "compatible with life".... even though sometimes I think he might be happier if we would all just piss off so he could freely play Playstation and conduct endless scientific experiments like the geeks on Myth Busters. Is there a difference between a nerd and a geek, by the way? I've always wondered.

Let's not forget, as well, that we all carry a pair of every chromosome. So Steve has one perfect cheese Twistie (chromosome 11) and one with a piece of chicken Twistie (22) tacked on. That one also is missing a little part of the cheese end. The same for his chicken one (chromosome 22) - one is perfect, all chicken, and the other contains a piece of cheese Twistie (11), and is missing a bit of chicken. Now he only needs to pass on ONE of each of his 23 chromosomes, and so do I, to make up a full set of 23 and a resulting bundle of joy. If he passes on his perfect chicken and perfect cheese Twistie, the result is Ella! If he passes on both the cheese and the chicken with the swapped pieces, the result is still fine - because it's balanced, like him! The pieces are all there, they're just swapped around (although that child, boy or girl, would have reproductive issewes like we're having when it comes time).

SO. Back to the translocation. The break points on Steve's two chromosomes at q23 and q11 are broken through particular genetic information. Still not lost, mind, otherwise Steve would not be *cough* normal.

But.... here's where it gets tricky *cue the dramatic minor key music*
Most of those little spermies (over 75% to be exact), each of which correctly contain just one of each of chromosomes 1-23, are carrying (for example) the chicken Twistie with the cheese piece tacked on and a perfect cheese Twistie (normal 11). This means, the missing chicken piece (22) is nowhere to be found. As well as that, there's too much cheese! That small section of genetic information is repeated, because not only is it on the normal cheese Twistie, it's repeated on the tacked-on bit on the chicken Twistie. There are various combinations that I won't baffle you with (there are about 18 variations, all told, which are specific to Steve and I.... they found that out doing our genetic mapping before we started the IVF), but basically out of those possible 18 we have about 3 or 4 which would result in a normal, you-beaut 'model'.

Anything else results in, thankfully I really do have to say, miscarriage. The chances of us actually carrying a chromosomally imbalanced (with too much chicken, not enough cheese, or missing chicken, you catch my drift) to term, whereby it hasn't stopped itself because there is just not the correct information for it to live and continue, is less than 3%. So there is an evolutionary trapdoor, if you will. I'm just the silly beggar who's having to do the incubating before it can be determined if this one's a goer time after time. That's the only bad part really. I'd rather have many miscarriages and a healthy baby if I can have any say at all (which I don't!). Let me give you the short list of defects our children are faced with if they don't spontaneously combust before we meet them (and they contain an imbalance):

Information from - Chromosome 22 Central:
"There are a large variety of abnormalities in t(11;22) cases. Cleft palate, heart defects, mental and physical delays, ear abnormalities, hearing loss, small chins, undescended testes (known as criptorchidism), microcephaly, dislocated hips, long philtrums, broad nose, kidney abnormalities, and imperforate anus are among the most common findings. Atrial septum defects, extreme muscle weakness, labial abnormalities, craniofacial dysmorphism..... unmanagable mental retardation."

Now, I don't know what some of these abnormalities are in detail, but I'm none too keen to find out.

Last year, we thought we had the 'right one' again - it didn't leave of its own accord in the first 9 weeks, so all appeared well on the surface, although we were still very cautious given our odds. I had the usual morning sickness, etc.... and at my first scan, discovered we had a severely behind little bubba with a very slow heartbeat. After a d & c, the pathology reports came back that she had too much chromosome 22 information (in fact, there were 3 full #22's! Steve had given her not one, but two... another one snuck in, so a true trisomy, like with Downs Syndrome on chromosome 23), and not nearly enough #11. And we made it to 9.5 weeks without even knowing. There are no precursors, no telling in advance, unless it aborts itself, if any embryo that implants is normal or imbalanced. Our only saving grace, that we can see, is that we are blessed with wonderful fertility, affording us the opportunity to attempt to continue our family at least twice a year....

So we wait. We conceive baby after baby and forge through countless miscarriages, despite the blinding unfairness of it all - I would rather experience a spontaneous miscarriage than have to terminate a live bub ever again, even though there was nothing to be done about that. It had to be done. And if it's got too much of one Twistie and not enough of the other, well, we will love it, will always love it and count it as one of our lost little soldiers..... but it needs to leave, and usually doesn't overstay its welcome anyway. We can wait for the right one.

Despite everything, Steve and I believe we have good grace about our losses. But really, it's called treading water, biding our time. There's nothing more we can do. We accept and we move on. The ache gets stronger the more losses we have, but it doesn't consume us because we've tended to build a resilience (which is not to say that we haven't painfully grieved each one).

UPDATE: We have finally welcomed a child into our waiting, aching arms...
and she's perfect.



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