Re: Role of 'Junk' DNA

On Thu, 13 Jul 2006 20:17:14 GMT, John Harshman
<jharshman.diespamdie@xxxxxxxxxxx> wrote:

michael.palmer1@xxxxxxxxxxxxxxxx wrote:

Treasures in the Trash
Matthew Herper Robert Langreth, 12.12.05
What genetic researchers used to call junk DNA may conceal the most
important medical secrets of all.

When researchers began mapping the genome, aiming to decode the entire
human gene sequence, they expected to eventually locate 100,000 or more
active genes. After completing the genome map in 2001, they were
startled to find that humans have only 25,000 active genes. The lowly
roundworm has almost as many (19,000).

That means the active genes contain a mere 1.5% of the 3 billion units
of DNAthat make up our genetic structure. The rest is "dark" or "junk"
DNA, long presumed to be present for no particular reason.

But researchers are now finding this junk DNA, overlooked for decades
by geneticists, may actually not be junk at all. They are finding hints
of an enormous and previously unimagined command-and-control apparatus
that regulates what our 25,000 genes do and how the body is assembled.
Junk DNA, when it goes wrong, may be a culprit in major killers ranging
from cancer to diabetes to infectious disease.

That insight could unearth hundreds of new targets for experimental
drugs that had been aimed only at working genes. "It's sort of like
Antiques Roadshow," says Harvard genome scientist John Quackenbush, who
has long argued that the junk DNA could be vital. "You look in the
closet full of junk and find out you have a Picasso."

"This will revolutionize human genetics over the next few decades,"
says David Haussler, a Howard Hughes investigator at UC, Santa Cruz who
was on the government team that decoded the human genome. He predicts
that most disease-causing genetic flaws will be found lurking in our
junk DNA.

The dark DNA "may be even more important" than active genes in causing
disease, says Isaac Bentwich, chairman of Israel's Rosetta Genomics.
Founded in 2000, Rosetta has applied for patents on 200 dark genes. He
hopes for new treatments and diagnostic tools for lung cancer, prostate
cancer and other diseases.

More at:
http://www.forbes.com/forbes/2005/1212/092_print.html

What is this article actually talking about?

For the most part, they are refering to miRNA's. These are small
(21-22 nt) RNA's that bind to mRNA and shut down translation when
bound. There are an estimated 800-1000 in humans. When comparing
sequences of them across species, they run the gamut from being fairly
conserved to species specific.

Then there are piRNA's, which are a bit larger (30 nt) and nobody is
absolutely sure what they do. To date, they have only been
demonstrated to be present in mammalian testes AFAIK. There are
thousands of these guys, scattered in largish clusters throughout the
genome. WHile the sequence divergence of these guys is much higher
than with miRNA, the clusters are syntenic.

Anyhow, the number of genes that are post transcriptionally regulated
by miRNA's is huge. They may act as a cellular rheostat, allowing for
very fine level of control of when a protein is expressed and at what
level.

B Miller

.

Relevant Pages

  • Re: Non-Coding DNA preserved by genetic drift?
    ... > supersede natural selection as the dominant evolutionary force, ... > Junk DNA costs energy to duplicate and to carry around as part of each ... > were plotted against the species' total genome sizes. ... > population sizes, more genes, more junk DNA and longer-lived gene ...
    (sci.bio.evolution)
  • Re: Role of Junk DNA
    ... When researchers began mapping the genome, ... startled to find that humans have only 25,000 active genes. ... But researchers are now finding this junk DNA, ... by geneticists, may actually not be junk at all. ...
    (talk.origins)
  • Re: Role of Junk DNA
    ... When researchers began mapping the genome, ... startled to find that humans have only 25,000 active genes. ... But researchers are now finding this junk DNA, ... by geneticists, may actually not be junk at all. ...
    (talk.origins)
  • Re: Role of Junk DNA
    ... When researchers began mapping the genome, ... startled to find that humans have only 25,000 active genes. ... But researchers are now finding this junk DNA, ... by geneticists, may actually not be junk at all. ...
    (talk.origins)
  • Re: Cold water on micro-RNAs
    ... There is a cost for replicating the genome, ... However your prediction that mutation and selection would quickly dispose of junk DNA is not solidly based. ... In eukaryotes the cost of DNA replication is a relatively small part of the cell's energy and materials budget, compared to bacteria where the cost of DNA replication is significant and junk DNA is essentially absent. ...
    (talk.origins)