Complex sentence: As reviewed by Farazi et al., abundant miRNAs can behave as "switches," turning some genes on or off, while for many miRNAs their altered expressions only lead to modest 1.5-to 4-fold regulations of their target genes.
Split into simpler sentences: As reviewed by Farazi et al., abundant miRNAs can behave as "switches," turning some genes on or off. However, for many miRNAs their altered expression only leads to modest 1.5-to 4-fold regulation of their target genes.