Organization of the 3.2 Billion Base Pair Human Genome

Less than 40% of the human genome functions in the manner expected prior to the "genomics revolution". Expressed exon sequences account for only 1.5% of the total genome. The balance of 'gene regions' comprise intervening introns, 5' & 3' promoter & enhancers, and other control regions that affect expression, and a number of pseudogenes that appear to have lost function, or gene fragments that have yet to gain them. The remaining 60% comprises a number of classes of repetitive DNA elements, including micro- & mini-satellite repeats, long & short interspersed repeats (LINEs & SINEs), etc, which are structurally significant but without clearly understood function. Individual repeat families such as the Alu family constitute >10% of the total genome, and may be moved among chromosomes as "jumping genes."

This DNA was previously referred to as "junk DNA", which simply reflected the state of ignorance at the time.

Figure ©2012 TA Brown, Introduction to Genetics (1st ed.); additional text ©2016 by Steven M. Carr