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BS: A genetics question
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BS: A genetics question |
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Subject: BS: A genetics question From: frogprince Date: 18 Jun 16 - 10:50 AM On the Science and Logic thread, Ed T linked to an article about potential elimination of a 3% risk of genetic defects in human reproduction. That reminded me of a question I have been meaning to ask: just (or, about) how accurate is the copying of genes in human reproduction? Is that "3% risk" essentially the same as saying that there is approximately a 3% chance that a given gene will be miss copied? Or is miss copying much more common, with most "mistakes" being harmless? Or am I asking something that would take 412 pages to answer in a meaningful way? |
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Subject: RE: BS: A genetics question From: Keith A of Hertford Date: 18 Jun 16 - 11:15 AM Though you may inherit a bad gene from one parent, the good version from the other usually takes over so the risk of impairment is much less than the risk of receiving a mutant gene. The bad gene will be passed to half the children so best not to have children with siblings or cousins. |
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Subject: RE: BS: A genetics question From: Mrrzy Date: 18 Jun 16 - 12:01 PM OK, well, there are various mutation rates for the various types of DNA, and those rates vary over time, but there is enough regularity in the system for molecular clock timing of genetic divergence... But a 3% risk as I undersand it is more that every generation, there is are changes in approx 3% of the DNA. Now, most DNA doesn't code for anything, so most of those changes will be in that most of the DNA that doesn't code for anything, so who cares. And, even for the tiny fraction that do happen in DNA that does code for something, the chances of it coding for anything that gets passed onto the next generation is minuscule, so you're still talking tiny, tiny changes that affect what gets coded for in the next generation. Which I would argue should not be eliminated as variation is not the spice of life but the necessary ingredient for there to be something for nature to select FROM, or we're doomed, like the cheetahs, who can't evolve anymore, they're all basically clones of each other, no more genetic variation left. |
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Subject: RE: BS: A genetics question From: TheSnail Date: 18 Jun 16 - 12:38 PM I'm doing a course on this at the moment. The figures given are that there is a copying error for one base pair in every 10 to the power of 10. The human genome has around 3 * 10 to the power of 9 base pairs so there will be a mistake in about one in every three cell divisions. As Mrrzy says, most DNA doesn't code for anything so there will be far less errors in actual coding DNA. As Keith says, that 3% isn't about the chance of making copying errors, it's about the chance of inheriting genes that have already been miscopied, possibly generations before, but have survived in the population because they are recessive. |
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Subject: RE: BS: A genetics question From: Steve Shaw Date: 18 Jun 16 - 05:57 PM Well it's a long time since I was forced to get my teeth into genetics, but I'll just add a few things. First, mutation is essential for evolution. Second, mutation can affect single alleles, sections of chromosomes or whole chromosomes. Third, mutations can occur in the formation of gametes or they can occur in body cells (resulting in cancer, for example). Fourth a mutated allele may be recessive against one allele but dominant against another. Fifth, there is such a thing as co-dominance. Sixth, most mutations have no effect on the phenotype. Only a tiny minority of mutations are either useful or harmful. Seventh, most traits are controlled by multiple genes, which should give pause to anyone worried about single-gene mutation. Eighth, mutation rate is affected by external agents, big time. UV, ionising radiation and some chemicals can all hugely increase mutation rates. Heavy smokers are thirty times more likely to get lung cancer than non-smokers, which is down to the chemicals in tar increasing mutation rate in lung cells. I could go on. Genetics is not my subject, but even so I'm wary of overly-simplistic statements from people even more non-expert then I am. Keith, for example. |
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Subject: RE: BS: A genetics question From: frogprince Date: 18 Jun 16 - 06:30 PM ...and why does my mutated spell checker reject miscopied? I should have known better than to cooperate with the damn thing. I recognize the basic importance of mutation, and certainly don't run around in fear of it; just got to wondering about the actual probabilities involved. Thanks for some education. |
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Subject: RE: BS: A genetics question From: TheSnail Date: 18 Jun 16 - 08:50 PM Hi Steve. When I sue the university that gave me one of my degrees for giving me misinformation, can I call on you as an expert witness? |
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Subject: RE: BS: A genetics question From: Steve Shaw Date: 18 Jun 16 - 09:00 PM Of course! Not only that, I'll only charge you mate's rate! |
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Subject: RE: BS: A genetics question From: mg Date: 19 Jun 16 - 04:12 PM another question...is it true that your father's mother's x comes to you straight from him, usually unchanged? |
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Subject: RE: BS: A genetics question From: Keith A of Hertford Date: 20 Jun 16 - 10:58 AM Your father's X came from his mother. If you are male, it does not get to you. If you are female, it does. |
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Subject: RE: BS: A genetics question From: Keith A of Hertford Date: 21 Jun 16 - 10:59 AM A father's Y chromosome is passed (unchanged barring mutations) to all his male descendants through the male line. The complete set of a mother's mitochondrial chromosomes are passed to all her descendants through the female line. |
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Subject: RE: BS: A genetics question From: Pete from seven stars link Date: 21 Jun 16 - 06:20 PM Evolutionary geneticist ,alexey simonovich kondrashov asked the question "why aren't we dead 100 times over ?" . I don't know that he offered a solution to the problem he posed. |
