Introns

In the 1970s, when scientists compared the sequences of DNA in genes with the sequences of RNA encoded by those genes, they made a puzzling discovery: the DNA of most genes in animals, plants, and other eukaryotes contains too much information. The extra segments of largely useless information were named introns, and they must be cut out of RNA before the protein is made. Exons are the portions of the gene that remain in the RNA after the introns have been removed.

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At every turn evolutionists are faced with inventing yet another story. But that’s ok because, to paraphrase dazz, they are used to it by now.

At some point in some lineage in the history of life it must have been advantageous to insert crap into the genome. But that’s simply not allowed, under the central dogma. Even so, some mechanism must have evolved to make it possible to insert crap into the genome, and then yet another mechanism evolved to remove the crap from the DNA so that protein could still be produced from genes in spite of the fact that genes had become filled with junk.

At some point, the evolutionary story stretches credulity.

Assume a gene without an intron. Now imagine a scenario in which some piece of crap of indeterminate length gets inserted into that DNA sequence. Imagine more than one. Imagine that protein manufacture continues unabated in spite of the insertion. Imagine now an imaginative mechanism arises to excise the crap out of the gene. Let your imagination run wild!

It’s simply difficult for me to believe that “it just happened, that’s all” is rational. It throws rationality, and science, out the window.

What is the most recent and the most plausible explanation for the rise and fall of introns?

302 thoughts on “Introns

  1. Allan Miller,

    Natural selection is impotent with respect to common ancestry so I don’t care what you say about it. You definitely cannot test the claim that NS is a designer mimic. Nothing of what Darwin posited has come to pass.

  2. I’ll admit I’ve said some stupid and confused things in this thread. And I probably misrepresented John Mattick. The reason I give is fatigue and rushed posts, but that is no real excuse. I will try to be more careful in future.

    That said I do think that people like Mattick should be taken more seriously. He does not deserve to be dismissed as being a crackpot.

    Below is the abstract of an article to which he contributed
    The extent of functionality in the human genome by John S Mattick and Marcel E Dinger in 2013

    Recently articles have been published disputing the main finding of the ENCODE project that the majority of the human genome exhibits biochemical indices of function, based primarily on low sequence conservation and the existence of larger genomes in some ostensibly simpler organisms (the C-value enigma), indicating the likely presence of significant amounts of junk. Here we challenge these arguments, showing that conservation is a relative measure based on circular assumptions of the non-functionality of transposon-derived sequences and uncertain comparison sets, and that regulatory sequence evolution is subject to different and much more plastic structure-function constraints than protein-coding sequences, as well as positive selection for adaptive radiation. We also show that polyploidy accounts for the higher than expected genome sizes in some eukaryotes, compounded by variable levels of repetitive sequences of unknown significance. We argue that the extent of precise dynamic and differential cell- and tissue-specific transcription and splicing observed from the majority of the human genome is a more reliable indicator of genetic function than conservation, although the unexpectedly large amount of regulatory RNA presents a conceptual challenge to the traditional protein-centric view of human genetic programming. Finally, we suggest that resistance to these findings is further motivated in some quarters by the use of the dubious concept of junk DNA as evidence against intelligent design.

    I believe the last sentence here is correct. Opposition to ID, and not a genuine search for the truth, is fuelling the arguments against the prevalence of functional, non-coding DNA.

    In the article they go on to say:

    The other substantive argument that bears on the issue, alluded to in the quotes that preface the Graur et al. article, and more explicitly discussed by Doolittle (Doolittle 2013), is the so-called ‘C-value enigma’ , which refers to the fact that some organisms (like some amoebae, onions, some arthropods, and amphibians) have much more DNA per cell than humans, but cannot possibly be more developmentally or cognitively complex, implying that eukaryotic genomes can and do carry varying amounts of unnecessary baggage. That may be so, but the extent of such baggage in humans is unknown. However, where data is available, these upward exceptions appear to be due to polyploidy and/or varying transposon loads (of uncertain biological relevance), rather than an absolute increase in genetic complexity (Taft et al. 2007). Moreover, there is a broadly consistent rise in the amount of non-protein-coding intergenic and intronic DNA with developmental complexity, a relationship that proves nothing but which suggests an association that can only be falsified by downward exceptions, of which there are none known (Taft et al. 2007; Liu et al., 2013).

    Timing is essential for the normal development of any organism and it is an especially complicated affair to get the timing right in the development of an extremely complex animal such as a mammal. And the splicing out of introns is all about timing. I would suggest that introns and other areas of non-coding DNA are important, not so much for their sequence of bases but for their length which affect the timing of gene expression and also the positioning in space of sections of DNA.

    And IMO regulation comes from above, from the individual cells and in multi-cellular creatures also from the individual organisms themselves.

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