Cell keeps spare set of DNA to ensure offspring gets fresh start

This is a little complex, but bear with us. Nearly all cells house their DNA inside a nucleus. But a little one-celled critter called Tetrahymena houses different versions of its DNA in each of its two nuclei. Researchers have found that the smaller nucleus (called the micronucleus) just keeps the cell’s full genome safe, acting as a sort of “lock box.” The larger nucleus (called the macronucleus) uses the DNA to regulate the cell’s life functions. When the cell mates to create a new generation, the two work together to compare the cell’s current DNA against what’s been stored in the lock box. If any foreign genes have snuck in (like from a virus) they nuclei eliminate it, to make sure baby gets a fresh start. Pretty neat, with possible implications for larger organisms, too.