Evolution of duplicate genes versus genetic robustness against null mutations

There are two proposed mechanisms for the emergence of gene network robustness: (1) 'genetic buffering' from redundant gene networks (i.e. alternative metabolic or regulatory or signal pathways), and (2) functional complementation from duplicate genes. Their relative significance is a subject to debate, but recent studies in functional genomics provide some interesting insights. In particular, experiments in yeast using whole-genome libraries of single-gene-deletion mutants and worm whole-genome RNAi show that both mechanisms are important for the genetic robustness. Yet, many questions remain.