A gene pool was a group of genetic materials present in a species.
Some gene pools were considered insufficient for creating a society. In 2365, Wilson Granger explained that the Mariposans initial gene pool of two women and three men were too small a gene pool, necessitating that they turn to cloning to increase their population instead. (TNG: "Up The Long Ladder")
As of 2378, Q Junior was, among other chaotic behavior, tampering with primordial gene pools. (VOY: "Q2")