tag:blogger.com,1999:blog-6030110973061875792.post561901174480035834..comments2024-03-16T21:32:23.088-04:00Comments on A Sure Word: “Mutations” Make a Creature More Evolved?RKBentleyhttp://www.blogger.com/profile/00566375018731000081noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-6030110973061875792.post-44070959251104091142012-06-08T00:16:33.571-04:002012-06-08T00:16:33.571-04:00Anonymous, I don't quite see the point of your...Anonymous, I don't quite see the point of your analogy. The proteins on the cells' surface have changed, allowing them to stick together. This much is understood by microbiologists. The <i>Chlorella</i> and yeast cells, themselves, don't seem to have altered their function, or to depend on any outside substance to help them adhere. That would seem more like some Lego blocks being modified so that they can stick together in the first place -- and displacing all other colors of Lego blocks because they're too big to be easily eaten.<br /><br />Once one has cells sticking together in the first place (all doing the same thing, at first, just as a cluster or ball), one can in principle cause some of them to specialize for particular tasks by establishing chemical gradients in the colony, that act more strongly on some cells than others (this is how the ball of cells that every animal embryo starts out as develops specialized tissues and organs). But that, as far as I know, has not yet been observed happening with unicellular organisms.Steven J.https://www.blogger.com/profile/15638850493907393069noreply@blogger.comtag:blogger.com,1999:blog-6030110973061875792.post-86071249470161761792012-06-07T23:09:56.331-04:002012-06-07T23:09:56.331-04:00jjk,
I've been busy with domestic duties and ...jjk,<br /><br />I've been busy with domestic duties and used what little free time I've had in the last two days to finish writing last post in this series. I hope you return and read it; I'm interested in hearing your comments on it.<br /><br />Anyway, I usually respond right away to Steven J's comments but haven't had a chance to yet. Thank you for stepping up. I liked your Lego analogy and wish I had read it before publishing my most recent post. With a little modification, I could have used it in discussing antibiotic resistance in bacteria. I'm sure I'll have the opportunity to use it in the future, with your permission.<br /><br />I've noticed that your comments post as “anonymous.” Do you blog, by any chance? I'd be interested in reading it if you do. If you log into Blogger before commenting, your comment will link back to your blog. <br /><br />Thanks for visiting and for your comments. Please come back. God bless!!<br /><br />RKBentleyRKBentleyhttps://www.blogger.com/profile/00566375018731000081noreply@blogger.comtag:blogger.com,1999:blog-6030110973061875792.post-64324134509778536062012-06-07T17:06:50.448-04:002012-06-07T17:06:50.448-04:00>> But being able to form groups of cells do...>> But being able to form groups of cells does sound rather like "added information" and "added complexity."<br /><br />I think not. Sounds to me either like an ability that is more prominent in the absence of other features, or the presence of something foreign introduced (or allowed for) by the mutation.<br /><br />On one hand the analogy would be fine dry sand, which will clump together when water is introduced.<br />The cohesion force between the introduced water and sand is larger than the adhesion between the sand particles itself when dry, yet it's still the same sand which acts differently (cells acting differently in the presence of something foreign, yet same cells) <br /><br />on the other hand, when the 'mud' now dries, the sand still stick together, since on a smaller particle level, the particles has changed arangement relative to each other (cells themselves looks different because of mutation) - yet the sand did not turn into metal or some other material, neither did the cell building blocks get new blocks introduced.<br /><br />Similar, you have blue lego blocks that are on average long pieces and green lego blocks that are short. Your mutation breaks off the knobs on most of your long blue lego blocks, now only the green lego blocks sticks, and a few blue ones .. what you build by random selection will look more clumpy.<br /><br />Yes, I know, it's not as simple on a DNA and atomic level, but the principal is.<br /><br />-jjkAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6030110973061875792.post-16696143865772382512012-06-06T01:57:25.703-04:002012-06-06T01:57:25.703-04:00Oh, I just remembered one: in a laboratory, scient...Oh, I just remembered one: in a laboratory, scientists introduced a predator into a colony of the single-celled organism <i>Chlorella</i>; this favored the evolution of a multicellular colonial form (a ball of cells). This new multicellular form persisted for several generations after the predator was removed, strongly suggesting that the change was genetic, not merely a pre-existing response to environmental change (of course, without the predator, the single-celled form again became fitter and mutations to resume that form would be favored by natural selection). Similar results were reported last year for the single-celled yeast <i>Saccharomyces cerevisiae</i>. <br /><br />You mentioned, in your post, that loss of eyes didn't make cave fish "more fit" overall. But then, so few traits do: a polar bear isn't "more fit" in a tropical jungle; a killer whale isn't "more fit" in a desert. Even multicellularity isn't "more fit" in an ecological niche better exploited by single-celled organisms. Indeed, there is a mutation (ccr5-Δ32) in humans that appears to make the bearer more resistant to HIV, bubonic plague, and smallpox, but more vulnerable to West Nile Virus. Beneficial or deleterious, or depending on circumstances? But being able to form groups of cells does sound rather like "added information" and "added complexity."<br /><br />At the wrecked Chernobyl reactor site, there are fungi that appear to be [a] more resistant to radiation than normal fungi and [b] appear to grow faster when exposed to radiation (i.e. they can use radiation to help make food). I don't see any sign that their genomes have been sequenced and compared to normal mold -- but the results are very suggestive.<br /><br />Note, in passing, that <i>E. coli</i> has been widely studied at the genetic level; more than one mutation is known that confers antibiotic resistance on the bacterium. So technically, that's several examples just by itself.Steven J.https://www.blogger.com/profile/15638850493907393069noreply@blogger.comtag:blogger.com,1999:blog-6030110973061875792.post-1257850874214802732012-06-06T01:36:16.834-04:002012-06-06T01:36:16.834-04:00Here is a problem: as far as I know, there has nev...Here is a problem: as far as I know, there has never been an Italian Wall Lizard Genome Project, so it is unknown whether the cecal valves that evolved in the intestines of Italian wall lizards stranded on the island of Pod Mrcaru depended on mutations or not. Such valves are unknown in Italian wall lizards on the mainland, so either there were beneficial mutations that helped build these structures, or natural selection can do rather more with pre-existing variation than you seem to imagine.<br /><br />Variations of this problem are ubiquitous, of course: very few of the millions of species on this planet are actually closely watched for changes (of course, when a mutation first appears, it will be rare and likely will be missed by casual human observers), or have their genomes examined to see if changes are the result of genetic changes or not. <br /><br /><br />Then there is the problem, when one has identified a mutation, of being sure whether it is beneficial or not. There's a known mutation in humans that leads to extra-dense, extra-hard bones, which (as you might expect) resist breakage better than ordinary bones. Whether the net effects of this make one more likely to pass on one's genes or not is not known. Likewise, there is an Italian family many of whose members have inherited a mutation that makes them more resistant to atherosclerosis (hardening of the arteries); this would definitely seem to be beneficial, but again, it's only been around a few generations.<br /><br />Note, again, that the black (<i>carbonaria</i>) morph of the peppered moth was never reported or described prior to the early 19th century, and appears to be, itself, a mutation that arose around the start of that century. Note in passing that the <i>carbonaria</i> mutation is dominant; it will not be masked by the gene for the grey morph.<br /><br />A rather different sort of beneficial mutation (it is beneficial to cattle ranchers and meat packers, and only beneficial to cattle because the breeders preserve them) is the "double-muscle" mutation in Belgian blue cattle. It seems unlikely to be useful in the wild, but it shows that mutations can give you more of something one already has -- and that might well be useful in other instances.<br /><br />You mentioned, as a possible example of the sort of mutation that would interest you, a mutation for blue fur in dogs. There are numerous observed mutations for new fur color in hamsters (domestic hamsters are all descended from a single pregnant female captured early in the 20th century), but they are colors already known from mammals. Blue feathers and scales are the result not of pigment but of structural features in the feather or scale; I'm not quite sure why such structural changes have never occurred in mammalian hair, but they haven't.Steven J.https://www.blogger.com/profile/15638850493907393069noreply@blogger.com