The ramifications of a new type of gene

WHAT’S a gene? You might think biologists had worked that one out by now. But the question is more slippery than may at first appear. The conventional answer is something like, “a piece of DNA that encodes the structure of a particular protein”. Proteins so created run the body. Genes, meanwhile, are passed on in sperm and eggs to carry the whole process to the next generation.

None of this is false. But it is now clear that reality is more complex. Many genes, it transpires, do not encode proteins. Instead, they regulate which proteins are produced. These newly discovered genes are sources of small pieces of RNA, known as micro-RNAs. RNA is a molecule allied to DNA, and is produced when DNA is read by an enzyme called RNA polymerase. If the DNA is a protein-coding gene, the resulting RNA acts as a messenger, taking the protein’s plan to a place where proteins are made. Micro-RNAs regulate this process by binding to the messenger RNA, making it inactive. More micro-RNA means less of the…

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