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' comprisi 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 is sometimes referred to as "junk DNA"

Figure ©2012 TA Brown, Introduction to Genetics (1st ed.); additional text ©2014 by Steven M. Carr