Younger genes are less likely to be essential than older genes, and duplicates are less likely to be essential than singletons of the same age

Abstract

Recently duplicated genes are believed to often overlap in function and expression. A priori, they are thus less likely to be essential. Although this was indeed observed in yeast, mouse singletons and duplicates were reported to be equally often essential. This contradiction can only partly be explained by experimental biases. We herein show that older genes (i.e., genes with earlier phyletic origin) are more likely to be essential, regardless of their duplication status. At a given phyletic gene age, duplicates are always less likely to be essential compared with singletons. The "paradoxical" high essentiality among mouse gene duplicates is then caused by different age profiles of singletons and duplicates, with the latter tending to be derived from older genes.

Fig. 1.

In both yeast (A) and mouse (C), genes with more recent phyletic origins are less likely to be essential, as are duplicated genes compared with singletons of the same phyletic age. However, ignoring age, the overall proportion of essential genes in singletons is higher in yeast (B) but lower in mouse (D) compared with duplications. Filled circles in (C) indicate that the proportion of essential genes in the corresponding duplication groups is higher than or closer to the overall P_E in singletons (41.1%; the dashed horizontal line); whereas hollow circles indicate that P_E is lower.