Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: kenhikage on 11/11/2010 13:33:55
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Evolution includes mutation. This is usually disadvantageous, but occasionally it allows some adaptation.
In a recent podcast it was said that some cancers act like an organ and set up "nests" for themselves. Certainly they are showing the same stubborn tenacity to survive that other forms of life show.
So, in trying to eradicate this parasitic lifeform couldn't we forever lose an evolutionary benefit? Or is the argument that evolution is no longer worth the sacrifice?
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>NB. As a non-biologist I'm having a go at answering this, so apologies if it's baloney!<
Evolutionary mutation is an utterly different mechanism.
It's the failure to make an exact copying of DNA at the point of fertilisation causing a 'global' rewriting of the code in the first cell of the foetus' DNA.
Cancer is by definition a run-away process of cell replication. I can't see how it could ever be beneficial.
Also, there is no mechanism for the rewritten code in the Cancerous cells to transfer from parent to a child, even if the mutation could have positive aspects.
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I see, I wasn't aware of that last bit. I thought that a tendency towards certain cancers was inheritable.
Thanks!
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Evolution includes mutation. This is usually disadvantageous, but occasionally it allows some adaptation.
In a recent podcast it was said that some cancers act like an organ and set up "nests" for themselves. Certainly they are showing the same stubborn tenacity to survive that other forms of life show.
So, in trying to eradicate this parasitic lifeform couldn't we forever lose an evolutionary benefit? Or is the argument that evolution is no longer worth the sacrifice?
It is evolutionary, I am sure. Is it an evolutionary benefactor of life? Is it therefor, an evolutionary mechanism working in junction of sustaining our own lifeforms. The answer is no. Cancer is a progressive, sometimes violently aggressive malignant entity which overcomes the host.
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Cancer is caused by a gene transcription error.
Uncorrected mutation in spermatogenesis, oogenesis, or perhaps blastocysts would be related to similar gene transcription errors.
Treatment of cancer, of course, would be different. But, as we learn more about genes, perhaps there will be an effort to reduce cancer susceptibility genes in the population, and in turn it would also reduce the new mutation rate in newborns.
Is this bad?
If Homo Sapiens evolved from monkeys over about 5 to 10 million years, then we would expect significant additional evolution over the next 5 to 10 million years, although potentially limited by dilution in a large population.
However, there could come a point where certain mutations would be vital for fighting disease. For example, there is a rare mutation that causes immunity to AIDS. If the disease continues to be an epidemic in certain areas, these AIDS resistance genes would be selected for. Could humanity get hit by a killer-flu that would select for other genes?
Other types of mutations could lead to a competitive advantage. However, we could select for something like Centenarian genes, but I don't believe that humans have the foresight to do so.
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Cancer, as a cause of death, is probably of evolutionary useful effect.
If you don't die, ever, then successful individuals tend to over consume resources, and reproduce too often, leading to inbreeding. Dying of cancer is one way that the genes can limit your lifespan.
Cancer can probably be prevented almost entirely by genetics, but it's not in the genes best interests to make your defences to it that good, by the time you get cancer, most of the time the genes have already copied themselves, so they (statistically) don't care about you so much any more.
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On average, if a person lives to the ripe old age of 30... the genes are already passed on to the next generation. So diseases that occur at age 50+ have little impact on the reproduction of the species.
Thus, it would likely take a significant amount of effort to select genetics that would lead to lifespans in excess of 100 years.
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Wolfekeeper, thank you for that answer. I understood very well your anthropomorphous explanation. In a related question, is "mutation" not the same as a "transcription error?"
Please forgive my long absence from these forums.
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On average, if a person lives to the ripe old age of 30... the genes are already passed on to the next generation. So diseases that occur at age 50+ have little impact on the reproduction of the species.
Thus, it would likely take a significant amount of effort to select genetics that would lead to lifespans in excess of 100 years.
Actually, that's not completely clear. It turns out that there's master genes that seem to control the amount of repair cells do. If you do a lot of repair you will age more slowly, and will accumulate genetic damage more slowly as well, which will tend to delay the point at which cancer occurs. However, it's complicated by various things, such as some cancers seem to be due to viruses.
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is "mutation" not the same as a "transcription error?"
Technically not I think, a mutation is any change to genes, whereas a transcription error is one cause of mutations.
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So, you could have a transcription error where the parent copy of DNA remains intact.
Or, one could have an event such as radioactive decay that damages the parent copy of DNA which may not be corrected, and is thus passed on.
Or, you could just run out of telomeres, which I suppose creates a certain type of transcription error at the end of the chromosomes.
Mutations involving meiosis (sex gametes) may have more evolutionary benefit than mutations involving mitosis (ordinary cell division) by diversifying the genes (which can also have devastating consequences), but may allow better response to environmental problems.
Mutations caused by short telomeres in general only affect mitosis, and not meiosis.
What is the evolutionary benefit of not producing adequate telomerase throughout life? Perhaps the evolutionary benifit of knocking off the old geezers to make room for the young whippersnappers?