In 1976, evolutionist Richard Dawkins eloquently described how he thought life on earth was characterized by selfish genes competing for propagation within the genomes of countless creatures.1 Since then, science has described unique segments of DNA called transposons that are able to insert copies of themselves into plant and animal DNA. Are transposons trying to take over their host genomes, thus demonstrating the selfish behavior described by Dawkins?
The answer is no. These mobile genetic elements—also called “jumping genes” for their ability to move from place to place—don’t just randomly invade a genome. Instead, they are now well-known for inserting copies of themselves into very specific places on chromosomes. Most animals’ genomes are loaded either with recently acquired and active transposons, or with remnants of transposons acquired long ago.
Perhaps the best-studied transposons are the “P elements” found in fruit flies. One still-active P element transposon appears to have been introduced into populations of the common fruit fly by another fruit fly species about 80 years ago. A recent study of P elements published online in the Proceedings of the National Academy of Sciences appears to have discovered the source of the “highly nonrandom selectivity of P element insertion”2
A Carnegie Institution for Science news release reported:
What many P insertion sites share in common is an ability to function as starting sites or “origins” for DNA duplication. This association between P elements and the machinery of genome duplication suggested that they can coordinate their movement with DNA replication.3
Somehow, these transposons “know” exactly where to insert themselves. And although they “remain highly ‘infective’ today,”3 they eventually stop “jumping” into new places in the fruit fly genome through inherited mechanisms of protein truncation and “piwi-interacting RNA” complexes.2 In other words, they eventually stop because of well-designed components in the host cell that interact very precisely with the transposons….
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