Discussion in 'Biology & Genetics' started by Dudeyhed, Mar 2, 2003.
what i mean is, how does DNA actually change?
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DNA can change in several ways. When it is being copied when a cell divides, errors can sometimes occur. Those errors can result in incorrect "letters", or in sections of the DNA being cut out, or in sections of the DNA being duplicated. To take an imaginary example, say the original sequence was:
Incorrect copies may include strings like:
Occasionally, DNA can also mutate, due to some kind of random chemical or atomic event. A mutation, like a copying error, can change one or more of the "letters" in a DNA sequence.
Hopefully a biologist can give you a more detailed answer.
That was informative but I really wanted to know how it happened in an evolutionary sense, like in conjunctuion with Darwin's theories.
How does an orgainsm genes change according to its habitat?
An organisms genes do not change because of its habitat. Evolution occurs through the mechanism of natural selection.
Heres an example. Theres a catapilar living in grassland. It is colord green. Any mutations that happen to make an individual a different color are unsuccessful because it is more noticable to predators in grassland. But say a few individuals move into a forested area. Suddenly, brown is a much more desirable trait to have, and will be 'selected' for. Not that evolution says 'you will survive better as a brown creature so I will make you brown', its just that over time certain mutations, in this case a brown colored mutation, will be brought out because its more successful. The brown caterpillars will have a better chance of survivng than its green parents.
Hope this helps.
Evolution is hard for me to conceptualize. I don't understand how random simple mutations can eventually make a sophisticated alteration.
For example, I would like to better understand mimicry. I don't think that initial mutations would be significant enough to select for, so how do the successive changes keep their momentum?
Changes to the DNA are incremental. Small changes add up over time to make big changes.
Let's take a very simple example. Consider a zebra or similar animal. Let's say that at some time all these animals were fairly slow runners, due to inefficient leg muscles, or disproportionately large bodies. Let's also imagine that these animals are preyed upon by some kind of predator such as lions.
In a large group of these animals, essentially all of them are slow runners, not very well adpated for escaping the lions. The lions can pick off pretty much any zebra they want. But, in the group, there will be random variations in the DNA which make a few animals able to run a bit faster than the others. Which ones will be more likely to be captured by the lions? Obviously, the slower ones. That means that any animals which are slightly faster will have more chance of surviving and having offspring, which will inherit speed from their parents. Over time, therefore, the faster animals will come to dominate the population. On average, all the zebras will be a bit faster than before. (At the same time, the lions will, on average, be improving in their ability to catch the faster zebras.)
Changes to the DNA are random, and usually not beneficial. Most changes are for the worse rather than for the better; only a few changes give the affected animal a benefit. However, natural selection is such that good changes tend to stay in the gene pool, whereas bad ones soon disappear because animals with the bad changes are more likely to die before reproducing.
Remember that evolution has millions of years in which to work, which amounts to hundreds of thousands of generations of animals (at least). A series of very small changes can lead to dramatic changes over the lifetime of a species - and it can also lead to one species gradually changing into another, or branching into multiple other species.
this only happens when the selection pressure keeps pushing for these mutations for several generations. A single dry year would not be enough...100 dry years in a row would be selective.
I undertand the principal of evolution and I understand natural selection. In your example, above, you refer to "a few animals able to run a bit faster". Is it possible for a single mutation to cause an animal to run faster?
<i>Is it possible for a single mutation to cause an animal to run faster?</i>
I'm not a biologist, but I'd say probably yes.
All of you above have done a great job… James: I’ll take over from here thanks you very much though.
Yes in fact there are many mutation scenarios in which just one would have a dramatic effect on the speed and endurance of an animal. Any one mutation that enhances the efficiency of the muscles, mitochondrion and vascular system would enhance physical performance. All this requires is a mutation in a gene that changes the amino acid sequence of a protein the gene makes. For your knowledge all life (with very minor exceptions) follows under the Central Dogma: DNA transcribed into mRNA and that is translated into protein and Protein does all work and makes life possible. The code of DNA decides the order of amino acid in the protein and the different amino acids determine the shape of the protein and its reactivity. Different proteins do very different things. A mutation in gene that makes a protein (or class of proteins) can change the shape of the protein and thus make the protein do new thing or enhance or reduce the efficiency of what it did (probably some catalytic reaction or structural purpose)
Well, we could look at it another way. Since Darwin's Theory of Natural Selection will probably never be proven, my theory is that intelligent beings from another planet genetically engineered us from primates. This is why scientists believe we 'evolved' from them and why the similarities between chimpanzees and man. This will never be proven either, but I believe this holds more water than the theory of natural selection.
<i>Since Darwin's Theory of Natural Selection will probably never be proven, my theory is that intelligent beings from another planet genetically engineered us from primates.</i>
Did they also genetically engineer all the other species, or did the primates evolve and then the aliens took the final step? If the latter, why draw the line just before humans? If you accept all previous evolution up to primates, it's only a small step from there to man.
On another point, it is true that the theory of natural selection will never be proven, but so what? No scientific theory will ever be proven. The question is: how much supporting evidence is there for one theory or another? In the case of natural selection, the answer is: heaps.
This is pure amateur speculation...
If the first people to come out of African 50,000 years ago populated the rest of the earth, then only 2,000(+) generations account for all of our genetic diversity. I have no idea what that number is, but I read that humans share 98.7 % of our DNA with chimpanzees, so that's < 1.3 % of 30,000 or 390 genes. About 1 mutation every 5 generations would be the average.
No every person shares about 99.9% with every other person or about 1-2 dozen gene difference. In fact only small mutations in genes that effect there relieve efficiency is what separates most people from each other. Chimpanzees on the other hand have a whole extra chromosome set (we have 46/23 pairs they have 48/24)
It depends on how you look at heaps. Really, when you look at it, there is no 'heaps' of proof for natural selection. You asked me about what about the animals, blah, blah, blah. Yes, they did, and they do, mutate, adapt-but they do not evolutionize! The small step to man, really didn't happen JR. The proof lies within the fact that chimps don't climb out of trees and turn into humans. So, the question is, why would animals mutate, and adapt, but this is more prevelant in insects, while primates don't? That is the real question. The other question is why did fish come out of the water and turn into lizards? There were no real threats-not like today with the loads of crap in the oceans! Why did lizards go up into trees and turn into birds? I believe the theory of natural selection is really science fiction. And I'm not really sure if you know this JR, but Darwin bawled his eyes out on his death bed. He was a Christian believe it or not-I'm far from it-and he realized what he had done with his theory. Science assumes this occured from fish coming out of the water etc., but why? Is it not possible that birds developed from one set of one-celled organizms, while fish, lizards, etc. from different types? Maybe even mutated types of one-celled organizms? Who knows? This is why I think the way I do. It's why I do draw the line at a certain point. All you have to do JR is open your mind just a little bit instead of trying to make me feel like shit because of your disregard to other people's opinions.
Your distinction between mutation & adaptation and evolution is a nice trick, but sorry, it's not working. Evolution (in genetic terms) is often described as changes in frequencies of alleles over time, which would incorporate both mutations and the adaptations from such mutations. Sorry.
Whether Darwin recanted or not on his deathbed means nothing. Which, BTW, is an urban legend.
As for chimps climbing out of trees and turning into humans - nothing in the evolutionary history nor anything in evolutionary theory maintains that occurred or will occur.
As for prevalence, take a look at genome size and rate of reproduction. A generation of insects can come and go in the course of a few weeks, having been exposed to selective evolutionary pressures. A generation of primates comes and goes in the course of decades. To say that humans don't have mutations is just denial.
As for the idea that various multicellular organisms are descended from separate populations of unicellular organisms, not in and of itself a bad idea, but once again, it fails to match up with the ribosomal RNA evidence from which a phylogenetic tree has been constructed. The commonality of various biochemical and genetic components across all species casts truckloads of doubt on that idea.
Not believing in evolution is like not believing in the sun or moon! Oh there is heaps of proof and it is not abstract either but as clear-cut as you can get! For one: How is it that all life is genetically related and that genes can even be traced back through different species? There is no competitive theory of the existent of life that can explain this as well as evolution!
About the apes coming out of trees and becoming human, jee that already happened!
And most of all what pisses me off most about creationist is they always claim that Genesis was right... oh ya first prove to me it was not a Hindu god or Buddha or Jupiter, Zeus or Thor that created all life and the Universe! How dare you attack science with religion when you still can't prove your self against other religions... when in fact you can't prove your self at all!
Cooked Fetus fetish whatever you call yourself
Did I say I was a creationist? You are one pompous peckerhead! I'm merely stating things the way I see it instead of the way schools taught you-governments fund schools don't forget that. And if you trust your government, you are too stupid to even comprehend what I said in my last string!
my theory is that intelligent beings from another planet genetically engineered us from primates.
Did you get that from that B-rated sci-fi flick, “Quatermass and the Pit (Five Million Years to Earth)”
What? What does government have to do with any of this? One of the thing the crazy government force me to learn was that it is a Ad Hominem fallacy to claim something is wrong because of the nature of its source. So evolution is not wrong just because the governments that teach it are corrupt and well... stupid. Try staying within the bounds of a critical thinking, it one of those things most governments force every university to teach to their students which is kind of odd considering that critical thinks skill also allow us to see what a bunch of fat cats and pigs our governments made of.
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