Organization of the Human genome
50kbp region of the human genome is shown in the middle
segment, with putative gene regions expanded above. Exons constitute only a
few percent of the region. Introns make up the bulk
of gene regions, and along with intergenic regions
are interuppted by repeat
sequences (cf. locus FLJ10143).
Many of the these dispersed repeats are members of the Alu
family, a 200~300 bp repeat dispersed many
hundreds of thousands of times across the genome.
Although repetitive DNA is sometimes referred
to as "junk DNA", this probably represents
the current state of unknowledge. For example, it
appears likely that repetitive elements assist in alternative
splicing of exons to produce different transcripts
with different properties from the same coding
region, which might explain how humans are able to
function with so few genes..