For an example and list of all knownexamples, see and .

Some thought introns were just another example of the apparentlynon-utile

Familiar examples ofprotozoa are flagellates (incl.

In terms of the hypothesis presented here, long open-readingframes would exist in certaingenes those genes had beenable to resolve the conflict in the regions where we now see the long open-reading frames;FORS-D pressure would have been accommodated by the choice of appropriate synonymouscodons or of amino acids with similar functions.

For example, an exchange of arginine for lysine (both basic amino acids) might suffice.

(termed the introns-late hypothesis).

Discussion about the origin of introns has been dominated by the idea, first put forward by Walter Gilbert (20), that exons were once separate genes and that introns are the present-day relics of the gaps between them when they were first brought together early in evolution. This is sometimes called the "introns early" hypothesis. The strongest evidence in favor of this view is the observation that where proteins consist of different domains, somewhat separate in the three-dimensional structure, and distinct even if mutually dependent functions, they are encoded by different exons (20). The heavy and light chains of immunoglobulins are good examples. And where pre-mRNA are spliced in different ways to yield functionally different protein products, it is clear that at least some of the introns mark the boundaries between rearrangeable protein domains that are functionally distinct modules. It is also true (see Gene Structure) that numerous multifunctional genes in eukaryotes are clearly homologous to separate single-function genes in bacteria, which are generally seen as more akin to the earliest organisms (though, in fact, they have been evolving for just as long as anything else).

Further examplesof gene duplication revealed through DNA sequence comparisons.

For example, Manfred Eigen of Germany's Max Planck Institute says, "There is no doubt that proteins, which are more easily formed, were first on the scene" .

Inactive Xchromosome of female mammals is an example of heterochromatin.


The RNA World and other origin-of-life theories. by Brig …

His error is identical to that of creationists who state that evolution could not happen because (for example) elephants are highly improbable.JM: I understand your objection to Senapathy's math in that example.

Today, research in the RNA world is a medium-sized industry

The math behind this reasoning is discussed at the start of Chapter 7, and text strings are used there as example "eukaryote genes" (pages 222-230).

The early description of cystic fibrosis (CF) dates back to late 30s

I agree that some clarity has been reached, but it is a clarity that allows us merely to begin sorting out the various hypotheses in the light of the accumulated evidence.

The atherosclerotic process is not fully understood

I should not be surprised to learn that it takes place in nature too,though I can't give you any specific examples.Actually, some work of this nature has already been done [on "testing if the entropy of non-coding sequences is higher than the one for exons"].

Developmental dyslexia - ScienceDirect

There was much excitement when the various domains of immunoglobulins seemed in accord with the Gilbert hypothesis, introns being located at domain boundaries (Robertson 1977).

05/12/2014 · Figure 1

Comparisons between homologous genes in different organisms give contradictory messages. Some introns have retained their positions, although not their internal sequences, over vast tracts of evolutionary time, but others come and go even between quite closely related organisms, often into and out of positions that cannot be considered boundaries between functionally distinct domains. The strict introns-early hypothesis, if anyone held strictly to it, would suppose that every intron position that we see now was there from the origin of the gene and that the reason that all the positions are not occupied now is that introns can be lost, most plausibly by gene conversion, when patches of cDNA replace the intron-containing genomic sequences. But as has been pointed out (22), if introns were present in the primeval gene in all their present-day positions, the exons must have been so short as to be incapable of encoding any functionally distinct part of a protein.