A link to the paper and to the figure you reference have been added to your original post by the Admin, making it easier to actually comment on the contents of your post.
peter borger writes:
After reading Spetner's book I realised that all it would take to overthrow NDT is molecular genetic evidence against the mechanisms of random mutation...
That mistakes occur in transmitting the genetic code from one generation to the next has been established beyond any reasonable doubt.
Scientifically speaking, we need only one example that is not in accord with NDT. It would question the validity of the concepts.
It would only "question the validity of the concepts" if it were a mechanism contradicting NDT, not merely missing from it.
The first paper I like to discuss with evolutionists is the paper by Schmid and Tautz published in a leading scientific journal (Schmid and K.J. and Tautz, D. A screen for fast evolving genes from Drosophila. Proceeding of the National Academy of Science USA 1997, Volume 94: p9746-9750.).
You draw conclusions from this paper in areas unrelated to the issues it addresses. Certainly the authors wouldn't agree with you.
It should be noted that evolutionists simply add all polymorphisms of the two species of Drosophila, and than they treat them as one species. In other words they compare apples with pears!
If you're talking about the figure, the authors do not add the polymorphisms together, they merely present them in the same table for comparison. Since the two species share a recent common ancestor, genetic similaries are expected, and the table shows this. If the two species were really as different as apples and algae (I can't use your analogy of apples and pears, since they, too, share a recent common ancestor) then they wouldn't even share this 1G5 gene.
They also discriminate between non-fixed (polymorphic) and fixed base substitutions. Obviously, fixed base substitutions are not taken into account. As a result, this biased comparison of distinct species does not say anything about the rate of evolution within one species. All it demonstrates is the difference between two homologous DNA regions of two distinct organisms.
And this is why you shouldn't attempt to draw conclusions outside the specific topic of paper. As the title of the paper clearly states, there were developing a screening technique for identifying fast evolving genes within the
Drosophila genome. Their technique evidently requires ignoring base substitutions. You can't draw conclusions about the consistency of the
Drosophila genome with mutational theory from this paper.
Similarly, introns in the 1G5 gene found in the subpopulations of D. simulans do not demonstrate variation at all. This is a very peculiar phenomenon, since the theory of neutral evolution says that the highest incidence of mutations is within the intron regions of a gene. It is assumed that intron regions are not subject to selection, and are able to mutate at random. This is not only expected between species, but also within subpopulations of one species. Yet, we do not see variation within the introns of subpopulations!
First, while introns are not expressed in the organisms phenotype, there are still clear limits on permissible mutations. In particular, they have to remain recognizable as introns else they may result in expression, which would be equivilent to a massive multi-nucleotide polymorphism and probably catastrophic to the organism.
Second, and orthogonal to the first point, with a data set of two introns your conclusions have practically zero statistical significance. The authors conclusions are inconclusive for the same reasons. Replication of this process by other scientists using other genes must be performed before, over time and only if congruent results are obtained, the author's results can become generally accepted.
In addition, have a close look at the positions of the mutations in the introns between the species. The intron exhibits 13 mutations; 10 out of 13 are immediately adjacent to each other (numbers 153-162). The chance that 10 mutations occur at random within an intron of 61 units equals 1.4 x 10(exp)-18. In contrast, the chance that a cluster of 10 adjacent mutations occur in the intron equals 2.2 x 10(exp)-14. Therefore, it is reasonable to assume that the cluster of mutations observed in the introns did not arise by a random mechanism. This is a very important observation, since it is molecular evidence evidence against random mutation. It is, of course, neither mentioned in the text nor discussed!
First, and as already mentioned, there are still clear limits on permissible mutations within introns.
Second, it's not mentioned in the paper because it isn't relevant to their goal of identifying a screen for fast evolving genes.
Another remarkable observation is that the 1G5 genes in subpopulations of D. melanogaster, as far apart as Australia, Russia or Canada are completely identical.
But don't forget the relatively local differences, such as between populations in Australia, and between populations in the US. Without speculating as to possible reasons, it doesn't seem like either simple migration or Noah's Ark account for it very well.
Over millions of years only a fraction of variation has been generated within subpopulations of Drosophila melanogaster in the so-called ‘very unstable’ 1G5 gene. In sharp contrast, a lot of variation is observed between the two species.
Uh, nothing else would make sense. Naturally there are fewer genetic differences within a species than between species.
Why does the 1G5 gene within a species stay nearly stable over time, whereas the same genes are highly variable within distinct sibling species?
The paper is about identifying fast evolving genes, and 1G5 was chosen because it is precisely that, a fast evolving gene. As they state in the introduction, the fast evolving genes were identified by comparison with
Drosophila virilis, which is thought to have diverged with
Drosophila melanogaster some 40-60 million years ago. They then compare the IG5 gene of
Drosophila melanogaster with
Drosophila yakuba, divergence thought to be 10-15 million years ago, in order to test their hypothesis that "under a neutral model of molecular evolution that a gene that shows a high divergence rate between species should also be polymorphic within a species."
In other words, the identification of fast evolving genes does not derive from the data in Figure 1. If you're trying to figure out how they identified fast evolving genes from this data you are doomed to failure because this is not the data they used. As far as I could tell, they don't actually present this data in the paper.
These misinterpretations suggest that a reassessment of your conclusion that the
Drosophila genome is "completely stable" might be appropriate.
It should also be realised that only approximately 30% of the D. melanogaster genome is polymorph and only 11 % is heterozygous. These percentages speak for themselves: the major part of Drosophila genes does not vary at all! They are completely stable!
Uh, without rate information the percentages mean nothing, and certainly 30% polymorph implies considerable variability for which you need some kind of source.
--Percy
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