Its mRNA does not code for any protein but instead directly interferes with other, larger mRNAs from different genes, blocking their translation. RNA strands suppress genes that inhibit developmental changes and thus act as timekeepers, controlling when the worm will move from one stage of its life-cycle to the next. If the discovery of this unusual mechanism in C. elegans was unexpected, then the finding that the same process with the same or a very similar RNA fragment may occur in almost all animals is remarkable. This suggests that the mechanism was already evolved in the last common ancestor of these groups. This provides strong evidence that let- 7 may be a universal developmental timekeeper.
Many questions still remain.
But this research adds to the growing evidence that we share far more of our genetic makeup and function with distant species than we might think. A tiny RNA molecule ensures that the larvae of a roundworm develop into adults. The discovery of this RNA in many other animal groups implies that this way of keeping developmental time may be universal. The Hox genes encode a class of transcription factors that are thought to be crucial for specification of body plans. This means that they are of interest to both developmental and evolutionary biologists, and differences in the expression of these genes could explain the evolution of animal phyla.