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What's the difference between genome-wide data and mitochondrial genomes?
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[QUOTE]Originally posted by Djehuti: [QB] [QUOTE]Originally posted by Doug M: [qb] An interesting related article: [IMG]https://media.wired.com/photos/5967b18e3a618c5f29276c7a/master/w_532,c_limit/SexGarbage_A_560Inline.jpg[/IMG] [QUOTE] For a species whose numbers show no signs of collapsing, humans have a shockingly high mutation rate. Each of us is born with about 70 new genetic errors that our parents did not have. That’s much more than a slime mold, say, or a bacterium. Mutations are likely to decrease an organism’s fitness, and an avalanche like this every generation could be deadly to our species. The fact that we haven’t gone extinct suggests that over the long term, we have some way of taking out our genetic garbage. And a new paper, recently published in Science, provides evidence that the answer may be linked to another fascinating procedure: sex. For about three decades, one of the senior authors of that paper, Alexey Kondrashov, a biologist at University of Michigan, has explored how populations might shed such mutations. The question poses more of a conundrum than you might think. One model of natural selection is that it acts on mutations one by one: letting this one stay, forcing that one out. Another, though, is that the fates of mutations can be linked—an effect that population geneticists call synergistic, or narrowing, epistasis. This might happen if having one mutation can compound the effects of another: for instance, a system that’s able to limp along with one defective piece will fail with the loss of a second or a third. In this way of thinking, for an individual, having more mutations is not just additively worse, but closer to exponentially worse. To Kondrashov and others, that prediction suggests an escape route from the trap of rapidly accumulating mistakes, both for humans and other multicellular organisms prone to mutations: As the number of nasty genetic errors in a population rises, natural selection will sweep large rafts of them out of the genome together. And in sexual organisms, because of the ways that mutations from each parent can recombine randomly onto the same chromosomes, the synergistic elimination of bad mutations can happen even faster. Kondrashov has investigated the implications of synergistic epistasis with theoretical studies. Other researchers have taken the experimental route, trying to detect whether, in real life, mutations can interact with each other this way. Those tests yielded mixed results, though, perhaps because the effect would not have to be very large to keep a population from succumbing. Now, however, Kondrashov and his co-authors have put together a statistical case, pulled from the genomes of about 2,000 people and about 300 wild fruit flies, that the effect has been quietly acting on us and other organisms all along. Drawing on knowledge of the species’ mutation rates and other factors, the scientists began by calculating what the distribution of mutations in populations of humans and flies ought to be in the absence of this purging effect. Certain numbers of individuals in the group, for example, ought to show 100, 50 or 30 mutations. Then the group of researchers turned to the genomic data, looking for the distribution of mutations in real-world populations.[/QUOTE] https://www.wired.com/story/what-if-sex-is-just-a-garbage-dump-for-genetic-mutations/ [/qb][/QUOTE]Actually the advantage of sexual reproduction is that it yields more genetic diversity. Mutation is the original source of all genetic diversity in all organisms both in asexual and sexual reproducing organisms however sexual organisms have an additional source of diversity through genetic recombination in that although the offspring inherits only half the genes from each parent, these genes recombine in ways that make the offspring genetically unique which is why with the exception of monozygotic (identical) birth siblings even siblings born at the same time but from different eggs and sperm differ from each other. Asexual organisms because they are identical are an entire population if not species vulnerable to disease. Because they are identical, what affects one individual will effect all of that population. Sexual organisms do not have that problem because of the great genetic diversity. The only way asexual organisms have any hope of surviving any onslaught against them is through mutation, but even some mutations may be harmful with those carrying those harful mutations usually dying before they reproduce. [/QB][/QUOTE]
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