Wednesday, April 4, 2007

Science!

I have had a few questions about my description of this blog, specifically as to what the "Law of Independent Assortment" means. Since, by day, I am a science teacher, I will do my best to explain.

When you are born, you get 2 copies of every gene. Genes are strings of DNA and you have 46 of these strings in every cell of your body. Each string has a pair - the one you got from mom pairs with the one you got from dad. These gene pairs will "code" (yes, you are a computer) for the same traits, for example hair color or foot length. So if mom was a redhead and dad a blond, you will have one gene that codes for red hair and another on that gene's pair that codes for blond hair. Or if mom was large-footed and dad a pee-wee you will have one set of code for large feet from mom and another set of code for small feet from dad. Usually, one gene wins and the other loses. That's nature, folks. So you end up be a blond like dad with no trace of red or a giant-footed wonder, just like mom.

Independent Assortment is what happens to our genes when we make nookie in a chevy and little Johnny boy steps out of the glimmer of his dad's eye and into the primordial goo of mom's uterus. When we make eggs or sperm, only ONE copy of each of those pairs makes it into the cell or sperm. It is a random choice. Little spindly fibers reach out and blindly grab one of each pair of genes to put in the egg or sperm. Mom's copy or Dad's copy. Doesn't matter. This is the Law of Independent Assortment. Our genes are "sorted" into eggs or sperm in a random manner, independent of any other forces. It makes sense - if we each gave all our genes, then the baby would have twice as many genes as we have. And their kids would have twice as many as them, and so on and so forth. Nature doesn't like this. Nature like the one copy from mom and one from dad paradigm. When this doesn't happen, miscarriages result.


"But, Megan," you may ask, "what does that fact that you have gorgeous red hair have to do with your cancer?" Excellent question, class. In addition to things we can see like hair color, our DNA and genes code everything in our body - internal structures, ("what a charming liver"), hormones, digestive enzymes, all the parts of our individual cells, etc... Our DNA is constantly making copies of itself for new cells. Your hair grows - new cells, you cut yourself and bleed - new blood cells. This is happening all over you body all the time. When your DNA copies itself for a new cell it goes very, very fast. Like a speedy typist, sometimes mistakes are made. One of the things that DNA codes for, in addition to hair color, is a small structure that acts like a spellchecker when the DNA is making copies.

So, here's where I tie in. Most people get two copies of that spellchecker, one from mom's gene's and one from dad's. I only got one from dad. Mom's was a dud copy that didn't have the right structure to spellcheck properly. (thanks for the cancer, mom!) This situation is called Lynch Syndrome or hnpcc. So, when and if my one good copy from dad takes a hit (from environmental mutagens, that bad steak I ate teeming with bacteria, or just chance) I am left with no spellchecker. And then my DNA starts to have all sorts of spelling mistakes, which (and I'm not sure exactly how this part works) turns it to a cancer cell. Or perhaps natural cancer cells in our body come to get rid of it since it's now a mutant cell. In any event, cancer cells cluster and, voila! A tumor.

I will spare you photos of the tumor. Although I may be willing to sell on eBay for the right price.

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