This complex trait is heavily influenced gucci shoes by genetics, Cohen's earlier research has shown. In a study published in 2009 in Science, he determined that just four DNA variants, called single nucleotide polymorphisms (SNPs), account for 90 percent of the efficiency with which yeast produce spores.

In that study, the researchers noted that yeast from oak trees produced spores with 99 percent efficiency; the vineyard strains were far less efficient, at 7 percent. Then, they put each combination of the four SNPs in both the oak and vineyard strains, to determine how the genetic variants interacted with one another.

The researchers showed that the four variants "interacted like crazy such that the combined effects of any four variants were always larger than the sum of their individual effects," Cohen says.

By developing a statistical model to account for the genetic interactions, they could genotype any combination of the four SNPs in either strain of yeast and predict with a high level of confidence their effect on sporulation.