Well, this is a little long, but I’d definitely like to hear what’s to be said about it.
So there’s this thing in your genome. Well, maybe not yours, but plenty of people’s. It’s called the PMP-22 gene. I don’t know what it does. It’s not really important until later. What is important is what’s in front of it. A region called CMT1A repeat. Hey, guess what’s it’s called a repeat! Cuz there’s two of them! One in front of PMP-22, one behind it! Here, let me draw a picture:
DNA: —-Proximal CMT1A repeat——–PMP-22——–Distal CMT1A repeat—–
This might seem really happy, huh? Well, it’s not. Because as you might remember from whenever you last took biology, our chromosomes do this crazy thing called crossing over. That’s during meiosis, which you might remember, is how you form gametes (eggs or sperm, depending), since they only have 1/2 the DNA of other human cells (which is why it takes two to make offspring!).
So, during crossing-over, homologous chromosomes (ex: both of your number 17 chromosomes, one from your mom, one from your dad) line up next to each other like buddies, and then they do this crazy thing where they both break a section of their DNA off, and swap sections with the other chromosome! Obviously, they it’s important that both chromosomes break at the exact same place, otherwise you could end up missing some genes! Usually this goes down just fine, since the broken piece wouldn’t reattach well if it didn’t ‘match’ the other chromosome’s broken end.
However, if you’re one of those unlucky ones who have the two CMT1A repeats, this is a problem! Because your body does not know which one is distal and which one is proximal! So chromosome 17 #1 might break at the distal location, and chromosome 17 #2 might break at the proximal location…. oh no!
Now chromosome 17 #1 has two copies of PMP-22, and chromosome 17 #2 has NO copies of PMP-22!!!
Now while the CMT1A itself is just a repeat, not a gene, it has no function. It doesn’t really matter if you have it or not, the PMP-22 is definitely a gene, and it is definitely important.
If you end up with two copies of PMP-22, you get Charcot-Marie-Tooth disease 1A. If you end up with ZERO PMP-22, you get neuropathy and palsies. Not fun!
So why do we have this repeat? Who put it here!?!? Well, it’s probably the old remnants of a ‘jumping gene’ – they copy themselves and reinsert themselves. They’re very random, though, so it’s very, very rare that they insert themselves into the exact same place in two different occurrences.
So why did God give us jumping genes? They’re kind of handy in evolution, but we all know God doesn’t believe in that, so why? They’re pretty dangerous – they can insert themselves right into the middle of a gene, rendering it useless! Dangerous!
Someone told me once that it was punishment for our sin. Ah, I see. Well, that’s a good Biblically correct answer. I know if someone I knew ate an apple when I told them not to I’d totally curse their children with genetic defects.
But wait, so, you’re saying that we have this repeat-crossing-over-problem with CMT1A because of our sins?
Well, I suggest you start preaching to chimpanzees and bonobos then, because they have the exact same defect.
That God, huh? Such a quirky guy!
Thank you, thank you! Have a wonderful evening everybody, and remember, evolution is real!