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' comprising 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 © 2012 by Steven M. Carr