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Theory of natural evolution says that complex life forms arose from simpler ones e.g. starting from Eubacteria to modern day multicellular eukaryotes. {If we try to reduce these changes happening at molecular level, it should be like, from Eubacteria like E.Coli. (20 kilobasepair genome/DNA strand size ) evolving, over time, to Multicellular Eukaryotes ( 3 Gigabasepair genome size) e.g. (humans and other hominids.)} Now if we see molecular changes happening inside cells, the molecular changes are within nucleus as extra nuclear changes are largely function of nuclear information (and a smaller extent external stimuli). For biochemical changes to take place inside cell Nuclear information is the major guiding force. But according to Central Dogma elongation of DNA shouldn't have happened as there is no scope for it in either doubling, translation or transcription. But actually it is not so according to evolution. So what allows changes to be imbibed in the DNA that also increases it's length ?

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closed as unclear what you're asking by David, iayork, WYSIWYG, Amory, Bryan Krause Sep 20 at 19:19

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    $\begingroup$ For incontrovertible evidence for duplication of the whole yeast genome see Molecular evidence for an ancient duplication of the entire yeast genome $\endgroup$ – user1136 Sep 9 at 12:38
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    $\begingroup$ Your question is unclear. One interpretation is that you think there is some principal of nature that would prevent DNA elongating, and you perhaps also think this is Crick's mistakenly-named Central Dogma. There is no such principle, and Crick's Central Dogma was that molecular genetic information transfer could proceed from DNA to RNA to Protein, but not from Protein to RNA or DNA. Regardless of what Crick said, gene expansion is known to occur and the mechanisms involved are understood and can be found from an internet search. Or did you mean something else? $\endgroup$ – David Sep 9 at 14:06
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    $\begingroup$ @iayork — You can say that the word Dogma was ill-chosen (Crick admitted he misunderstood the meaning of the word) and that it is dangerous to give students the idea that there are dogmas in science. Or you can say that the concept is so obvious now that we know the mechanisms of gene expression that it is difficult to justify teaching it as such. However the expression "outdated concept" suggests that it is incorrect. It is not. Suggestions about the nationality of the OP and the teaching of science in India are not relevant, and I suggest you think about withdrawing them. $\endgroup$ – David Sep 9 at 14:14
  • $\begingroup$ Yes exactly if information flows from DNA to RNA to protein and in no way from protein towards DNA than how come the changes that happened in external environment (that should mostly affect cellular cytoplasm and not nucleoplasm) went to the DNA and made such changes that started getting reflected in offsprings of the organism (as adaptation to the environmental change that happened). More intriguing is the fact that Nuclear DNA in modern primates have genome size of up to three gigabase pairs but there is no mechanism described that elongates the DNA. $\endgroup$ – user240988 Sep 10 at 2:04
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DNA misreplication events can lead to accidental duplication of DNA (even the entire genome), misalignements in recomibination events, integration of DNA from extracellular sources e.g. viruses. All these events can lead to large scale changes in the genome size of an organisms, smaller scale changes can be insertions and deletions in the DNA from repair pathways such as non homologous end joining.

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