Selfish DNA
<p><b>Selfish DNA </b>is a term for sequences of DNA that <i>sensu stricto</i> have two distinct properties:
--the DNA sequence spreads by forming additional copies of itself within the genome; and
--it makes no specific contribution to the reproductive success of its host organism. (It might or might not have significant deleterious effects.)
 
The difference between <b>junk DNA, and selfish DNA</b> is quite large. One has no apparent function, the other has as a clearly defined function, just one that doesn’t (usually) benefit the organism whose genome that selfish DNA is hanging out in.
 
<b>Transposons</b> are anything but random DNA. Some contain whole genes that produce proteins devoted to duplicating the transposon. Others don’t even go to that much effort, but instead simply contain recognition sequences to fool the proteins made by other transposons into helping them move.
 
<b>A transposon (or transposable element)</b> is a small piece of DNA that inserts itself into another place in the genome. Geneticist Barbara McClintock discovered these genetic elements while studying corn in the 1940s.
 
In the human genome, over 98% of DNA is classified as noncoding DNA and can be transcribed to regulatory noncoding RNAs (i.e. tRNAs, rRNAs), origins of DNA replication, centromeres, telomeres and scaffold attachment regions (SARs).
 
Noncoding regions are most commonly referred to as 'junk DNA', however, this term is misleading as noncoding DNA does have functional importance.
 
The proportion of coding and noncoding DNA within organisms varies and the amount of noncoding DNA typically correlates with organism complexity, though there are many notable exceptions.
 
<b>noncoding</b>
DNA which does not code for protein
<b>intron</b>
a portion of a split gene that is included in pre-RNA transcripts but is removed during RNA processing and rapidly degraded
<b>intergenic-intron same</b>
describing the noncoding sections of nucleic acid between genes</p>