The phrase "known genes" refers to genes that scientists have discovered, studied, and have a good understanding of. These genes are well-documented and their functions are generally known. Full definition
A small number of known genes, it is thought, account for nearly 50 percent of pigment variation. (sciencedaily.com)
Her message: Not even the experts can distinguish a 1 from a 4 if they don't know the genes. (scientificamerican.com)
The scientists also demonstrated that predicting hair colour with this new genetic information is more accurate than with previously known genes. (sciencedaily.com)