Oxytricha trifallax lives in ponds all over the world. Under an electron microscope it looks like a football adorned with tassels. The tiny fringes are the cilia it uses to move around and gobble up algae. What makes Oxytricha unusual, however, is the crazy things it does with its DNA.
Unlike humans and most other organisms on Earth, Oxytricha doesn’t have sex to increase its numbers. It has sex to reinvent itself.
When its food is plentiful, Oxytricha reproduces by making imperfect clones of itself, much like a new plant can grow from a cutting. “If they’re well fed, they won’t mate,” said Laura Landweber, a molecular biologist at Princeton University and lead author of a recent study on Oxytricha genetics. But when Oxytricha gets hungry or stressed, it goes looking for sex.
When two cells come together (as in the image above), the ultimate result is: two cells. “They’ve perfected the art of sex without reproduction,” Landweber said. The exterior of the two cells remains, but each cell swaps half of its genome with the other. “They’re entering into this pact where each one is going to be 50 percent transformed,” Landweber said. “They emerge with a rejuvenated genome.”
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In size, Oxytricha’s genome is roughly comparable to ours. It has about 18,500 genes, compared to 20,000 or so for humans. But that’s one of the few things we have in common with this pond-dwelling protist.
Read the full, original story: This bizarre organism builds itself a new genome every time it has sex
