Junk DNA

Jay Mone jaymone at paonline.com
Thu Apr 13 21:40:11 EST 2000

Here's a question for everyone to chew on...

It is generally agreed that of the human genome, only about 20% is used for
coding of information or other known functions.  What are the prevailing
thoughts on why the other 80% of our genome seems to do nothing but take up
space, and how we came to have so much junk DNA?

In my general biology class, I often pose these questions to my students for
thought.  As to how we came to have so much junk DNA, I have no idea.  Might
this junk DNA actually provide a selective advantage?  Having so  much
wasteland in between the coding regions of the genome certainly reduces the
probability that a mutation will occur in a coding sequence or it's
regulatory region.  It would be like trying to hit a tent in the huge desert
by randomly lobbing missiles over the entire desert.  Its unlikely that
you'll hit the tent.  Since mutations occur virtually every time a cell
divides, this might be a mechanism to lessen the effects of such random
mutational events.  Does this sound reasonable?  Has this or another idea
been put forth recently?  And how did we come to get so much junk in the
first place?

By the way, in the other genomes sequenced so far (C.elegans, Drosophila,
etc, do they also have large amounts of junk DNA?

Jay Mone'

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