Fig. 3

Size distribution and starting nucleotide of the conserved and other known miRNAs. The relative abundance of different size categories (a), from 20 to 24 nucleotides is shown for the conserved and other known miRNAs presented in Fig. 2. The relative abundance of the 5′-nucleotide (b) is shown for the conserved and other known miRNAs presented in Fig. 2. In 31 miRNA families, 21 nt long miRNAs were the most significant size class. In 32 of the 40 conserved miRNA families, the majority of sequences started with uracyl at their 5′-end, although a portion of these have a different nucleotide composition at position 1 to a variable degree. Three miRNA families exhibited a preference for an adenine at position 1