Because genomes are products of natural processes rather than “intelligent design,” all genomes contain functional and nonfunctional parts. The fraction of the genome that has no biological function is called “rubbish DNA.” Rubbish DNA consists of “junk DNA,” i.e., the fraction of the genome on which selection does not operate, and “garbage DNA,” i.e., sequences that lower the fitness of the organism, but exist in the genome because purifying selection is neither omnipotent nor instantaneous. In this lecture, I review the concepts of genomic function and functionlessness from an evolutionary perspective, present a precise nomenclature of genomic function, discuss the evidence for the existence of vast quantities of junk DNA within the human genome, discuss the mutational mechanisms responsible for generating junk DNA, spell out the necessary evolutionary conditions for maintaining junk DNA, outline various methodologies for estimating the functional fraction within the genome, and present a recent estimate for the functional fraction of our genome.

 

Dan Graur is John and Rebecca Moores Professor in the Department of Biology and Biochemistry at the University of Houston, Texas and Professor Emeritus of Zoology at Tel Aviv University, Israel. Having earned a B.Sc. (1978, Biology) and an M.Sc. (1980, Zoology) at Tel Aviv University, he completed a Ph.D. (1985, Genetics) at University of Texas Health Science Center at Houston with Dr. Masatoshi Nei. Following a short postdoctoral fellowship at the University of Tübingen in Germany, Dr. Graur was appointed Lecturer at Tel Aviv University (1986), where he was promoted to the rank of Professor six years later. Coauthor of two editions of Fundamentals of Molecular Evolution (Sinauer Associates, 1991 and 2000), Dr. Graur has published close to 200 articles, book chapters, encyclopedia entries, commentaries, technical notes, and book reviews. His book Molecular and Genome Evolution is about to come out in September 2015. Dr. Graur was one of the founders of the Society for Molecular Biology and Evolution, and has served as Associate Editor of Molecular Biology and Evolution (1995–2011) and Genome Biology and Evolution (since 2009). He received an Alexander von Humboldt Lifetime Research Award in 2011 and, in 2014 was elected Fellow of the American Association for the Advancement of Science. In addition to his research in molecular and genome evolution, Dr. Graur is interested in the societal implications of genetics and molecular biology.