I almost don't want to do this. It entertains an awareness of what we may be faced with 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).
Steve has a non-Robertsonian 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'd be me husband) is normal, often not aware of their uniqueness until they try to have offspring or give birth to an unbalanced baby.
Have I lost about half my readers here? I'm so sorry, but some of you were asking...
Anyway, what happens is this (and it's sooo hard without diagrams):
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. The larger the chromosome with a 'problem', the greater you could expect the defect. In other words, a chrom 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 (oh I'm so brilliant, they look exactly like Twisties in the pictures I've seen!), 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. That's the only bad part really. I'd rather have many miscarriages and a perfect kid than wish for anyone, no matter how severely disabled, to make it here. Now before any pro-lifers or sensitives to disability snub their noses at me, 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 the hell criptorchidism is, but I ain't too keen to find out. That's some scary, scary shit. And this list isn't even exhaustive. This is just what they've studied from known cases, people who have allowed the examinations.
I think I'm lost. I hope it's prego brain... prego brain caused by a N-O-R-M-A-L embryo deep in the folds of my cushy womb room. And if it's got too much of one Twistie and not enough of the other, well, I love it, will always love it and count it as one of our lost little soldiers..... but it needs to leave. A (short, because they don't live to ripe old ages most of these kids) lifetime of disability and pain is not worth it just to satiate some need we have in us. Nup. I can wait for the right one. Last year, we thought we had the 'right one' again - it didn't fall out in the first 9 weeks, all appeared well. I had the usual morning sickness, etc.... and at my first scan, discovered we had a severely behind, slow heartbeating, little bubba. 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.
Now can you see why I can't get excited for weeks yet? And why I can wait through countless miscarriages, despite the blinding unfairness of it all (I'd rather a spontaneous abortion (ugh, ugly term) than have to extract a live bub)? And why we, Steve and I, have good grace about our losses? It's called treading water, biding our time. There's nothing more we can do.
Thank you and please read up to page 581 in your text before the next lecture. If I haven't lost anyone and you understand all this, you've passed the lesson.