Genome Duplication Is A Radical Evolutionary Gamble

Arthur T Knackerbracket writes:

https://www.quantamagazine.org/genome-duplication-is-a-radical-evolutionary-gamble-20260902/

No larger than the head of a match, Potamopyrgus antipodarum doesn't look very impressive. Few people visiting New Zealand's Lake Alexandrina even notice the tiny gastropods littering the shores. The snail's diminutive size, however, conceals a massive secret. Sometime in the recent past, its genome doubled. Instead of having two sets of chromosomes and two copies of every gene, the way most animals do, it has three or four - significantly more genetic material than it ought to have.

"We actually don't know, for our snails or any other species, why this happens so reliably, again and again and again," said the evolutionary biologist Maurine Neiman, who studies the species at the University of Iowa.

Scientists suspect that an organism inheriting three, four, or more sets of chromosomes instead of two (a condition called polyploidy) is, in most cases, a fatal error of cell division. Only a tiny fraction of whole-genome duplication events are thought to stabilize in a lineage. But those that do can have significant consequences.

You wouldn't be able to guess, but these snails have three or four sets of chromosomes in their cells, instead of the standard two.

"We like to think of it as a baseball hitter that strikes out a lot, but when they do hit, it's a home run," said Douglas Soltis, a plant evolutionary geneticist at the Florida Museum of Natural History. "Polyploidy is the most important process on the planet that hardly anybody knows anything about."

Advances in whole-genome sequencing are changing that. Studies across the tree of life are finding that genome duplication isn't exactly an infrequent occurrence. Among plants, it's hard to avoid, said Jonathan Wendel, an evolutionary biologist at Iowa State University: All seed plants living today have experienced at least one ancient whole-genome duplication, and many have undergone more. Barnacles, insects, trout, and arachnids carry evidence of ancient duplications in their genomes. Biologists hotly debate whether the significant evolutionary changes that led to jawed vertebrates, from hagfish to humans, are connected by ancient gene duplications hundreds of millions of years ago.

The evolutionary biologist Maurine Neiman uncovered a whole-genome duplication in a minuscule snail. "We actually don't know, for our snails or any other species, why this happens so reliably, again and again and again," she said.

Like gene inversions and translocations or single-nucleotide point mutations, a whole-genome duplication is a type of genetic mutation that fuels evolutionary change. In fact, genome doubling is the single most radical mutation an organism can experience in a single generation. Researchers are analyzing the whole genomes of diverse species to find out how organisms manage not only to survive such a potentially lethal event, but also to thrive and adapt in its wake. "All these different interrogative tools have opened up this world to us that we could not see and hence did not know existed," Wendel said.

A story of how this process unfolds is being written in potamo's genome. Neiman's team dated the snail's genome duplication to less than a million years ago - incredibly recent in evolutionary terms, but long enough ago for the species to have begun the longer process of adjusting to its heavier genomic load. That recency is giving Neiman a close view of how potamo has managed its polyploid existence.

This is the latest evidence amid a growing awareness of polyploidy that is shifting science's understanding of genome duplication's evolutionary importance. The serene shores of Lake Alexandrina are about as far from the Las Vegas strip as you can get, but that didn't stop potamos from taking one of evolution's biggest gambles.

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