The only way to stop creationists like me claiming to be evolutionists is to include the theory that all life evolved from a single-cell-like organism in the defintion of evolution.
I am unable to change the definitions of scientific terms; and I am fairly indifferent if you want to make obviously false claims about yourself. For all I care you can claim to be a chocolate-coated revolving umbrella stand.
If the antibiotic came first, this means the mutation that confers immunity wasn't present in the original population. So how did any bacteria survive the antibiotic if none of them had the immunity mutation?
If the antibiotic came first, this means the mutation that confers immunity wasn't present in the original population. So how did any bacteria survive the antibiotic if none of them had the immunity mutation?
The effect of an antibiotic depends on its concentration: a concentration which is not universally lethal will still inhibit growth and reproduction, which acts as a selective pressure in favor of mutations conferring immunity.
Let us consider a not uncommon evolutionary event. A population of bacteria is exposed to an antibiotic. A mutation arises conferring immunity.
Actually this is an uncommon event. Frozen samples retrieved from the remains of the Franklin Expedition showed a small proportion of antibiotic resistant members. This probably IS a mutation but it exists before the bacteria is exposed to antibiotics. The reason it is at such low levels initially is that it is a defect that is detrimental and only gives a net benefit when exposed to antibiotics.
Similar results have been found from other samples from before we started using antibiotics in medicine.
The antibiotics cause a strong negative selection against the dominant non-resistant members allowing the resistant members to rapidly increase in numbers. This is one reason that antibiotic resistance can arise within a few years; as has happened historically; the resistance was already there.
Actually this is an uncommon event. Frozen samples retrieved from the remains of the Franklin Expedition showed a small proportion of antibiotic resistant members. This probably IS a mutation but it exists before the bacteria is exposed to antibiotics. The reason it is at such low levels initially is that it is a defect that is detrimental and only gives a net benefit when exposed to antibiotics.
Similar results have been found from other samples from before we started using antibiotics in medicine.
The antibiotics cause a strong negative selection against the dominant non-resistant members allowing the resistant members to rapidly increase in numbers. This is one reason that antibiotic resistance can arise within a few years; as has happened historically; the resistance was already there.
Well, the "already there resistance" didn't help those 20 million people people who died as a result of the Great Flu...
Actually this is an uncommon event. Frozen samples retrieved from the remains of the Franklin Expedition showed a small proportion of antibiotic resistant members. This probably IS a mutation but it exists before the bacteria is exposed to antibiotics. The reason it is at such low levels initially is that it is a defect that is detrimental and only gives a net benefit when exposed to antibiotics.
Your reasoning is unclear. I said that both can happen: the fact that one has happened on at least one occasion does not mean that the other one is uncommon.
If I told you that people can be either male or female, and that it was not uncommon for them to be male, would you try to refute me by triumphantly producing a single example of a woman?
But in reality over time the neutral ones would most likely become deleterious.
How? What does this mean?
Any gene that has collected a huge number of "alleles," most of which of course don't do anything, is one of those parts of the genetic code that is especially prone to mutations. So such mutated "alleles" that get passed on are going to easily accumulate more mutations until finally they do something decidedly unbeneficial to the host. It's inevitable since mutations are inherently destructive.
Four for a gene should be all it takes to provide all the variety we see for any given trait ...
I have given you examples about the coat color and markings of dogs where this is not the case.
Perhaps I didn't see it or thought it too silly to bother with. Your job is to repeat your case. abe: And by the way, there are exceptions to most rules [/abe]
quote: Any gene that has collected a huge number of "alleles," most of which of course don't do anything, is one of those parts of the genetic code that is especially prone to mutations. So such mutated "alleles" that get passed on are going to easily accumulate more mutations until finally they do something decidedly unbeneficial to the host. It's inevitable since mutations are inherently destructive.
If there are a lot of variations it is more to do with selection than mutation rate. Which suggests that the gene tolerates quite a lot of variation - or even that variation may be beneficial. The most variable genes seem to be related to the immune system - and I can certainly see reasons why variation might be beneficial there (the weakness of a monoculture should be well known)
Are you talking about variations in the function of the gene or in the sequences of its many alleles? I'm talking about the latter, and I'm supposing that those alleles are just the usual useless mutations, everything from "neutral" or having no effect on the function of the gene, to destructive. I'm further supposing that a gene only has those four natural alternatives or alleles that would have been possessed by Adam and Eve or any two individuals. So, taking this into account, what are you saying again?
abe: If the most "variable" genes are those that have to do with the immune system, rather than suggesting anything beneficial, it doesn't bode well for us. And we do seem to be prone to more and more immune deficiency diseases. A friend of mine died two years ago from a sudden onset of such a disease; he'd been quite healthy sand suddenly experienced severe muscular deterioration from such a disease I forget the name of. It was six months from its onset to his death.
quote: Are you talking about variations in the function of the gene or in the sequences of its many alleles?
Not every sequence variation gets counted as an allele, you know. If you want to count those you'd have even more variety to explain.
quote: ...and I'm supposing that those alleles are just the usual useless mutations, everything from "neutral" or having no effect on the function of the gene, or destructive
"Destructive" variations are only likely where the function of the gene - or rather the protein it codes for - is detrimental. Again, selection is a major factor in what we see.
quote: I'm further supposing that a gene only has those four natural alternatives or alleles that would have been possessed by Adam and Eve or any two individuals.
Making false assumptions will tend to lead you to false conclusions, although I don't think this one matters greatly apart from prejudicing your thinking.
Anyway, I am saying that your point is wrong. Genes which gave a lot of variants must tolerate variation well - or selection would reduce the number of variants. And there are even genes where it is likely beneficial to the species to have many variants.
So genes with many variations are less likely to be "harmed" by mutation.
However your original point as stated was even worse. An existing allele can only become harmful through environmental changes, and there is no way to say that environmental changes are particularly likely to target genes with many alleles (and no way to say that they would be more harmful to later variations than to a presumed original)
Anyway, I am saying that your point is wrong. Genes which gave a lot of variants must tolerate variation well - or selection would reduce the number of variants.
Not if they are predominantly the "neutral" kind that are unaffected by selection. They'll just stay in the system without effect until more changes accumulate to become destructive.
And there are even genes where it is likely beneficial to the species to have many variants.
Such as? If the "many variants" are neutral differences in the DNA sequence, that don't affect the function of the protein, they aren't going to be beneficial OR destructive. But if a mutation is destructive in itself, then such changes in the sequence are likely to be ticking time bombs that can become destructive as they continue to accumulate mutations. If they kill the host then they'll be selected out, yes, but since we're all accumulating lots of these mutations, an accumulation of such destructive effects is to be expected.
So genes with many variations are less likely to be "harmed" by mutation.
You keep using that term "variations" in a vague way. If a gene can only have four naturally occurring variations, all the different "alleles" that have a neutral effect would be ticking time bombs as I say above, prone to accumulate more mutations until finally they threaten the organism. And get selected out, but meanwhile lots more of those are accumulating.
However your original point as stated was even worse. An existing allele can only become harmful through environmental changes,
This is an overworked assumption that is no doubt not true where it counts: most genetic diseases are going to get you no matter what your "environment." It's all in the changes to the gene itself, not the environment. There's no way an immune-deficiency muscle wasting disease could possibly be beneficial no matter what the environment.
and there is no way to say that environmental changes are particularly likely to target genes with many alleles
Quite true but as I said in most cases the disease is in the allele itself and not in the environment.
(and no way to say that they would be more harmful to later variations than to a presumed original)
The "later changes" represent an accumulation of mutations that increases the chance of producing a disease, quite apart from the environment.
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