Amazing that only half a century ago we were just discovering the structure of DNA and its method of duplication. Then came myriad questions about how DNA produces characteristics.
Before we answered even a fraction of those questions, we discovered epigenetics, the system of molecules that mark and control DNA. Here came another multitude of questions and discoveries. Some of those epigenetic markers are methyl groups (a carbon and three hydrogens).
Now John R Bracht has reported on a ciliated protozoan, Oxytricha trifallax, which uses the same methyl groups to mark junk DNA for the trash.
According to an article in TheScientist, this organism reproduces asexually when food is plentiful.
However, it has an astonishingly complex reproductive cycle for times when food is scarce. During this cycle, the cell has up to 8 nuclei. Some of these are used exclusively for preserving the entire genome for reproduction, while others shed over 90% of the genome by getting rid of methylated "junk" sections and keeping only what is currently useful.
And this is all happening in a single-celled creature! What an awe-inspiring result of evolution.