Researchers in the last several years realized that they have overlooked whole classes of genes that do not make proteins. Normally, a short stretch of DNA is translated into an RNA molecule which is then moved to another part of the cell and decoded to make a protein. While the non-protein coding genes also produce RNA molecules, these products are not used to make protein.
About 15 years ago scientist started to see that some RNA did other things than make proteins. For example, the Xist RNA controls deactivation of one of the X-chromosomes in females, a necessary process to prevent biological problems. No one yet understands how the Xist RNA actually works.
These non-coding RNA genes often to regulate the levels of protein-coding RNAs but some have other functions too. It turns out there are many genes that do not make proteins--many more than realized until even just a few years ago.
The new article, Genes Don't Only Make Proteins: How Non-Coding RNA is Revolutionizing Genomics discusses how these genes were discovered and their impact on genomics research.