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  Topic: Non-coding DNA, What is the current state of research< Next Oldest | Next Newest >  
Alan Fox



Posts: 1391
Joined: Aug. 2005

(Permalink) Posted: Mar. 29 2006,20:44   

IIUIC

In all organisms known, DNA sequences are a one-dimensional code that produce amino acid polymer sequences. The three dimensional folding is an inherent property of only L-isomers being incorporated and the subsequent inevitable folding and functional activity inevitably follows from the one  dimensional code. Some polypeptides and proteins act as switches to produce the necessary mix of gene products required for that cell or organism to develop and function.

Roughly 2% of the human genome fulfills this role and the purpose(s) of the remainder , the non-coding DNA, are not yet understood.

The life of a single-celled green alga does not (appear to me to)involve complex strategies. Take in light energy, grow and divide as much as conditions permit. A human embryo is packed with the information that under the right conditions will produce a new-born infant, with the potential to develop into a highly intelligent individual with a huge capacity to learn and use new strategies. Between the two is a whole spectrum of multicellular organisms with a wide range of innate and learn-able strategies.

Whilst I don't normally expect to find scientific answers at UD, A question by DaveScot set me thinking about  how the socially organised behaviour of termites, for instance, be accounted for in the genome. Does current research indicate any possible function for non-coding DNA. One might expect redundant DNA to be lost over time, but not only is it retained but the sequences are highly conserved.

I would be most interested to hear any new developments.
I am also curious as to why "Junk DNA" could affect the vacuity or validity of ID

  
jeannot



Posts: 1200
Joined: Jan. 2006

(Permalink) Posted: Mar. 29 2006,21:12   

Quote (Alan Fox @ Mar. 30 2006,02:44)
Does current research indicate any possible function for non-coding DNA. One might expect redundant DNA to be lost over time, but not only is it retained but the sequences are highly conserved.

Some non coding regions have a structural role, especially near the centromere, AFAIK.
Evolution does not predict the reduction of size for non-coding DNA, otherwise it wouldn’t exist. In fact, an important proportion of non-coding DNA is made of transposable elements, which replicate themselves in genomes, like parasites. Transposable elements represent 70% of the maize genome for instance. This is a case of selfish gene that can increase its fitness (replication rate) without (apparently) increasing the fitness of its owner. This clearly does not support Intelligent Design.

  
Alan Fox



Posts: 1391
Joined: Aug. 2005

(Permalink) Posted: Mar. 29 2006,21:22   

Quote (jeannot @ Mar. 29 2006,22:12)
Evolution does not predict the reduction of size for non-coding DNA, otherwise it wouldn’t exist. In fact, an important proportion of non-coding DNA is made of transposable elements, which replicate themselves in genomes, like parasites. Transposable elements represent 70% of the maize genome for instance. This is a case of selfish gene that can increase its fitness (replication rate) without (apparently) increasing the fitness of its owner. This clearly does not support Intelligent Design.

I can see that the replication property is an inevitable consequence of the structure of DNA; its "selfishness" if you like. So why is non-coding DNA stable in amount and conserved in sequence. If it were parasitic, might one expect the amount of parasitic DNA to expand, even exponentially.

Or is it a case of reaching a stable equilibrium, where host/parasite both survive optimally?

  
Chris Hyland



Posts: 705
Joined: Jan. 2006

(Permalink) Posted: Mar. 29 2006,23:56   

There is a large amount of functional noncoding DNA in the genome that is nessecary and therefore wont be lost. Promoter regions and telomeres are an example, but there are also many functional RNAs that are transcribed but not translated that play many vital roles including Post-transcriptional regulation, cell differentiation, cell death regulation, developmental regulation, dosage compensation, chromosome inactivation and DNA demethylation to name a few. Im not sure what this has to do with ID, I imagine the argument is that ID would predict that a designer would not leave useless DNA in the genome. However since scientists have known about functions of non coding DNA for about 20 years Im not sure if the argument carries much weight.

  
Alan Fox



Posts: 1391
Joined: Aug. 2005

(Permalink) Posted: Mar. 30 2006,00:01   

Thanks Chris

I can see Google is going to be my friend here. You've given me plenty to search.

  
Alan Fox



Posts: 1391
Joined: Aug. 2005

(Permalink) Posted: Mar. 30 2006,00:07   

Sorry, Jeannot.

Thanks for your reply.

(Peut-ętre tu pensais est-ce que que c'est comme ça qu'on se tient?)

  
jeannot



Posts: 1200
Joined: Jan. 2006

(Permalink) Posted: Mar. 30 2006,00:08   

Generally, non-coding DNA is not so stable in amount or sequence, AFAIK. I remember the case of the fugu fish (I think) that seem to have lost a large amount of its non-coding DNA. Also, the amount of non-coding DNA in prokaryotes is rather low.
And non-coding sequences have a high mutation rate.
Also, some junk DNA is the result of genome duplications (common in plants) followed by gene silencing. The variation in genome size among angiosperms is pretty huge.

“Parasitic DNA” cannot expand indefinitely since it would certainly reduce the fitness of its owner at some point. Then you might ask “so, even a low level of transposable elements in a genome can be counter adaptive?”. It could be, but sometimes transposable elements can be adaptive; some of them carry resistance genes. Barbara Mclintock (Nobel price in the 80’s) demonstrated that transposable elements in maize are “activated” by abiotic stress. (I’m not an expert on this subject.)
Also, remember that transposable elements derive from viruses (and vice versa), so maybe they can move from “host” to host and replicate inside genomes even if their replications are counter adaptive for their hosts.
Actually, transposable elements cannot exactly be qualified as non-coding DNA, since they can be “activated”, but I think some of them can be completely deactivated at some point.

  
Alan Fox



Posts: 1391
Joined: Aug. 2005

(Permalink) Posted: Mar. 30 2006,02:45   

Parasitic DNA.

I may need a few wet towels.

  
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