The Minimal Genome Project
The Minimal Genome Project was a study headed by Craig Venter that attempted to find the smallest working set of genes necessary for an organism to live and reproduce successfully. The chosen organism for study was the bacterium Mycoplasma genitalium, an obligate intracellular parasite, because of its naturally small genome. The experiment consisted of random gene knockouts, with each knockout mutant being tested for signs of life.
Roughly one third of the knockouts that resulted in a non-viable mutant were from genes that had a function that was unknown at the time.