Partial correlations among the birth year, degree, importance, and expression level of yeast genes.

aBirth year is the year during which the gene was first included into the PPI (or GI) network. Degree is the number of interactions the gene has in the PPI (or GI) network in year-2007. Importance is the amount of fitness reduction caused by the deletion of the gene in yeast. Expression level is the expression level of the gene in the mid-log phase of yeast growth measured by microarray. Relationship between two properties (shown before I) is studied when another one or two properties (shown after I) are controlled for.bTwo-tail test.