DNA that is apparently nonfunctional, insofar as it does not encode proteins or essential RNA molecules, or perform any vital regulatory role, e.g. in controlling gene expression. The term was coined as early as the 1960s and formalized by the Japanese-US geneticist Susumu Ohno (1928–2000) in 1972. Only 1.5% of the human genome codes for proteins, ribosomal RNA, or transfer RNA, with another 5% representing regulatory sequences, roughly 20% comprising noncoding introns within genes, and a further 15% being noncoding DNA of unique sequence between genes. The remaining 58% is made up of multiple copies of repetitive DNA and transposable elements, such as the Alu family. However, projects such as ENCODE have revealed that around 80% of the human genome is transcribed in at least one cell type, leading to the assumption that much of the ‘noncoding’ DNA must have some function. But what constitutes a useful function has been questioned; much noncoding DNA accumulates mutations without any noticeable harmful effects, indicating that the base sequence is not critical to its function, or it serves no useful purpose at all. Hence, functional DNA may account for only 8–14% of the total. See also selfish dna.