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