The Elements of Evolution (42-4) DNA Mavens

  DNA Mavens

It’s one of Nature’s early attempts to become more complex despite staying small in the sense of being unicellular. ~ American evolutionary biologist Laura Landweber

Oxytricha trifallax is a pond-dwelling ciliate: a single cell roughly 10 times the size of a typical human cell. Extensively studied, O. trifallax is typical of its genus.

Oxytricha has mastery of its genome: employing some of the same biological mechanisms that normally protect chromosomes from falling apart to construct the contents of the germline nucleus that it bequeaths its offspring. Oxytricha does this by intelligently sorting through ~225,000 DNA sequences.

Oxytricha’s working macronucleus is also unusually complex. Whereas humans have only 46 chromosomes, Oxytricha have 16,000.

Oxytricha has sex solely to exchange DNA, not to reproduce. Oxytricha spawn daughters asexually.

Oxytricha don’t bother mating if well fed. But if stressed and feeling the need for genetic diversity, Oxytricha seek sex.

2 Oxytricha fuse and share genetic information while mating. The object is for each cell to replace aging genes with lively DNA from its partner. This sexual encounter takes about 2 days.

It really is like it’s running an algorithm, and it’s a cellular computer. ~ Laura Landweber

Together, mating Oxytricha construct new working nuclei with a selectively fresh set of chromosomes. This both diversifies their genetic material and rejuvenates them.

They stop aging by trading in their old parts. ~ Laura Landweber