Posted on 02/08/2002 5:40:18 AM PST by JediGirl
Scientists have discovered the first genetic evidence explaining how small mutations can cause big changes in an organism's body.
Until now there has been little proof that one genetic change can successfully lead to a whole new species.
A University of California study has shown how a mutation in a 'master gene' which controls others could lead to a major body change.
The study looked at a class of genes known as Hox, which switch on and off other genes during an organism's development as an embryo.
The San Diego team used brine shrimp to prove a simple mutation here suppressed 15% of the limb development in the animal's central body region.
This would have allowed its ancestors, which had limbs on every segment of its body to lose their hind legs and evolve into six-legged insects.
Professor William McGinnis, who led the study, claims it answers the question as to how evolution can introduce big changes into an animal's body shape and still generate a living animal.
He said: "Creationists have argued that any big jump would result in a dead animal that wouldn't be able to perpetuate itself.
"And until now, no one's been able to demonstrate how you could do that at the genetic level with specific instructions in the genome."
Story filed: 12:41 Friday 8th February 2002
How do you define evolution?
Something like "the creation of existing species from ancient ones thru purely natural means related to variation & inheritance, filtered by natural selection, dumb luck ("genetic drift"), & maybe other factors."
The blood clotting article was very interesting. Is blood clotting considered a mutation or do hemophiliacs just have a deleterious mutation?
The duplications & retargetting of the original genes for pancreatic serine proteases are mutations, yes.
From one of the links:
- Antibiotic resistance in bacteria appears to be a beneficial mutation along with insects becoming resistant to pesticides.
- Bacteria that eat short molecules (nylon oligomers). Is this considered a benefical mutation or a change?
- Sickle cell resistance to malaria is not a beneficial mutation. According to the link "it provides a change", but "is an example where a mutation decreases the normal efficiency of the body".
- Lactose intolerance. I have this "mutation" and don't consider it beneficial! Help me out here. Why is this considered beneficial?
- Resistance to atherosclerosis. This looks like a beneficial mutation.
- Immunity to HIV. I hope I have it.
The mosquito link was interesting and it looks beneficial.
I appreciate the info on mutations. Prior to your posts I had only heard of sickle cell resistance as a mutation and then it was not considered beneficial. As I pointed out, the link states this mutation is still not considered beneficial.
Ah, but that illustrates what I said about traits being beneficial or harmful in context of the organism's environment. The mosquito's mutation is beneficial if they live in areas where pesticide is being sprayed. If they live in pesticide-free areas, then I guess the altered gene would be pumping out enzymes that the mosquito doesn't use. At the least that would be a waste of energy, & I'd expect it to eventually disappear by being selected out of the gene pool. (Like those fish who live in underwater caves, whose eyes don't work anymore.) Same thing as those nylon-eating bacteria. Sickle cell is a recessive trait, and if an African has just one copy of the gene, their red blood cells are just sickle-shaped enough that they have resistance to malaria. The really bad effects of sickle cell anemia kick in when the person has both copies of the sickle cell gene. Only then is it really debilitating. But in a malaria mosquito rich environment, it's an optimal tradeoff.
While I have no problem seeing some of the mutations as beneficial, I have yet to understand how the mutation supports evolution. I have no problem with a mutation supporting microevolution. But for me it stops there. Do you consider the mutations to support anything other than microevolution?
Yes. Enough mutations of the right types would eventually make the separated population incompatible with the original one. Creationists assert that there must be some as-yet-unseen barrier on a genetic level against speciation, but they've never shown that such a barrier actually exists. Meanwhile there are all those speciations that have either been seen in "real time" or are known to have occurred since historical times.
LOL, I see where your confusion lies. "Artemia Ubx HA" is the name of the construct with the reporter HA attached to it. Drosophila embryos containing this construct were conveniently labeled as such.
And then, the general statement (pulled from elsewhere, I assume), "The San Diego team used brine shrimp...". This statement says nothing, of course, about constructing transgenic shrimp embryos. Yes, they used brine shrimp. They used a very specific gene from the brine shrimp.
I hope that clears up the confusion.
The group studied DNA from adults who were lactose intolerant and compared them to sequences from adults who were lactose tolerant. They found that the specific mutations accounting for lactose intolerance were all in the same region of DNA (outside of the coding region btw), identical for peoples from widely ranging geographical areas. What's more, lactose intolerance (non-persistence) is more prevalent than lactose persistence. It's an obvious conclusion that that lactose intolerance is the normal, baseline condition.
You were bringing up infant lactose intolerance in the context of this study, even after I pointed out that this was an unrelated condition. In this congenital disease, the lactase enzyme is completely missing or non-functional. It has nothing to do with the recent study of adult lactose persistence.
Have you ever seen a termite mound? There are no architectural blueprints for such a mound. Nor is there one termite or even a panel of termites directing the others. Each termite is aware only of its surroundings and has no idea of the large project it is involved in. It just carries on according to a few rules of interaction between it and its immediate environment. Yet, a structural, complicated whole emerges.
The mind boggles. Verily 'tis the work of the Intelligent Designer.
</creationism mode>
OK, just so we are clear that this is ONE PIECE of a puzzle. A puzzle that may have many thousands of complicated pieces that may or may not have to be laid out in a certain place and order to go from shrimp to fly.
Are you saying that other pieces of the puzzle could never be demonstrated similarly? Or that all the changes for each puzzle piece had to happen simultaneously?
No and no. Don't see how one could get that from my post (#84 or 92?). Your #78 imlied that only 17 changes in amino acids were required to go from shrimp to fly. You now say to make this 'one piece of the puzzle' it would only take those changes. That is more like it. But we have always known that you could make a fly from shrimp DNA if you could make enough changes to that DNA. But is there a viable chain of organisms for every possible change required along the way? Not all of the changes would have to happen at once, but many would have to occur in conjunction with others for the new organism to be a viable one. Is there a possible path between the two? And even if possible, is there enough time for it to have reasonably happened by chance?
If only ten mutations were required to go from shrimp to fly, scientists would have long ago proven evolution by making new critters from old ones.
I think I'm confused about your point.
I think you and aruanan might be making the same point. And this is a complicated question. It's not one that the current study sought to address, although everyone would have been tickled pink if they had been able to combine the multiple changes necessary for a complete transformation of one organism to another. Of course, we know there is a possible path between the two. There are probably a whole collection of possible paths between the two.
Give me a break, this isn't evolution, this is genetic engineering.
A "you-really-hit-the-nail-on-the-head" BUMP.
Here, it is shown, that only ten mutations account for a major body plan change. That's saying a lot. Now we know it isn't necessaryfor a zillion improbable small mutations with clumsy intermediate forms to occur to make major changes in morphology. The next step is to show the simultaneous change and interaction of two genes. Back to the bench!
Late sleeper, huh? :-)
Enough mutations of the right types would eventually make the separated population incompatible with the original one.
What part, if any, of your defintion of evolution controls or directs the "mutations of the right types"?
By "incompatible" I assume you mean speciation.
Creationists assert that there must be some as-yet-unseen barrier on a genetic level against speciation, but they've never shown that such a barrier actually exists.
That cannot be correct. Most if not all creationists that I've read have no problem with speciation. I know I've heard about this barrier, but from everything I know, creationists don't claim it's at the species level; rather it's at some higher lever, although at what level I cannot say.
Meanwhile there are all those speciations that have either been seen in "real time" or are known to have occurred since historical times.
As far as I know, real time speciation is not an issue for anyone. It's speciation that's been "known to have occurred since historical times" that is the issue. That's the real bone of contention, so to speak.
Brine shrimp???????? I thought that the California brine shrimp was an endangered species. Aren't they the reason used by the greenies to keep people from filling in mud puddles thereby denying them use of their own land? Why is this lab committing these inhumane experiments on a protected species?
There you go again! Is this 'one piece of the puzzle' or is this the sum total of the changes needed? Or are you substituting 'next step' for 'puzzle piece' here?
I would feel highly confident betting my house that those 10 changes are not the only changes needed to go from a shrimp to a fly. I am 100% confident that many other changes must occur along the way. If it were otherwise you guys would have already turned tanks of radiation bombarded shrimp into swarms of flys!
The question is, how big can the steps be? This experiment indicates bigger steps are possible. But it does not say which of those steps may lead to organism death if not accompanied by other changes, or even if there are steady footholds between two of the steps.
That statement is from the top of this thread, fifth line.
Exactly - same old story. Evolutionary biologists have shown this before, but in all cases it is taking something away or producing a cripple (ie the four-winged fruit fly). This is not evidence of evolution.
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