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Randomness in chromosomal crossover

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Randomness in chromosomal crossover

Postby Iamu » Sun Feb 22, 2009 2:37 am

What factors determine whether or not there will be chromosomal crossover at a particular site during meiosis? Is it an essentially random process?

And if it is random, is it a chaotic deterministic process, or is it truly random--for example, could it be influenced by truly random quantum-scale events?

I'm an undergrad studying physics. I'm very enamoured with quantum mechanics, and I'm wondering if random quantum processes play a significant role in determining the development of a human being, or if we are essentially classical, deterministic machines. It seems that quantum randomness doesn't factor strongly in how our brains and bodies operate--our life processes operate at the classical scale. I can imagine a world where, if chromosomal crossover is also deterministic, we are all forced to follow a (more-or-less) deterministic course, but I can also imagine a world where everytime we reproduce, we can actually end up with any one of all viable combinations of the mother and father's DNA, and so we could end up with a very different person each time.

I know its fanciful of me to think this way, and I'm probably oversimplifying things, but I'd really like to know just how much of what happens on Earth is actually up to chance.
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Re: Randomness in chromosomal crossover

Postby wbla3335 » Sun Feb 22, 2009 10:12 am

Theoretically random, but check out "hotspots". At least in humans, recombination is not particularly random. Personally, I don't think quantum indeterminacy has much influence at the biochemical level. But there are those who do, and they are not all quacks, eg. Roger Penrose. Best we leave this an open question because, frankly, no one yet has any strong evidence for or against. As far as reproduction goes, we DO end up with a different person each time. Each and every sperm may not be genetically unique, but to get two identical people, two identical sperm would have to each fertilise two identical eggs, and that's not too likely to happen (we're not considering monozygotic twins here). If you're interested in things like free will, determinism, etc., have a look at "Freedom Evolves" by Daniel C. Dennett. He's a philosopher AND a Darwinian, a rare combination.
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