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Why is DNA preferable to RNA as the genetic material?

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Why is DNA preferable to RNA as the genetic material?

Postby Stacey » Tue Sep 06, 2005 8:38 pm

What makes DNA preferable to RNA, proteins, or carbohydrates as the substrate for storing and retrieving the genetic blueprint of anything larger than a virus? Why is RNA not good enough a material to support larger genomes?

...Could someone please elaborate on this statement: "The genetic stability and the chemical inactivity of double-stranded DNA have been regarded as favorable molecular properties for its role as the carrier of genomic information."

Thanks :D
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Postby baikuza » Wed Sep 07, 2005 11:02 am

...
i hope u can understand what i have said-english is my 2 language
as much as i know DNA is more complex than RNA,
at many kind of cell the organel of cell which has DNA(e.g. myticondrion,cloroplas, nucleus) can duplicate it self while the cell,entirely, weren't at telophase-see reprodustion of cell. so i concluse that only DNA can do that job, not RNA
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Postby victor » Wed Sep 07, 2005 11:44 am

Oops...not only DNA, but RNA also can do it a long time ago before DNA exist. DNA subtitute RNA as genetic material database because DNA is more stable and DNA can store much more genetic informations better than RNA..(just compare the length between double-helixed DNA with the single-stranded RNA).
When you see, the more complex the organism, the much more gene space that they require for expressing their genome..so??back to evolution again.

For the statement: as I said above, DNA is more stable because it's double helixed so there're bases pairment with Hydrogen bond for each bases that make DNA is more stable at storing genetic information.

Hope this answer your question
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Postby CynMari » Wed Sep 07, 2005 12:23 pm

so also, the double helix helps to protect the DNA against mutation since the damaged section can be repaired by pairing nucleotides with the undamaged strand...

but then I am wondering...
how does the cell/enzymes know which strand is damaged?
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Postby victor » Wed Sep 07, 2005 12:36 pm

Maybe they know it because it's expressing the odd amino-acids within the translation..so, they fix it.
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Postby canalon » Wed Sep 07, 2005 1:24 pm

victor wrote:Maybe they know it because it's expressing the odd amino-acids within the translation..so, they fix it.


No. Protein cannot be "proofread" this way. In fact differnt system exist:
- mutation during DNA replication: USe of methylation to detect which strand is newly synthesised, and which is the template
- Degradation of (a) base(s): exision of the degraded base(s) and replacement (possible errors if 2 bases have the same degradation product)
- Reparation by homologous recombination, usually for long damages. Even possible in bacteria if problems occur during replication. Not always 100% faithful.

This is a very simplified version of what can happen. Search Medline for DNA repair, you will see it is a very complicated thing :)

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Postby baikuza » Thu Sep 08, 2005 7:08 am

Sorry...

I forget that not all of the species in this world has DNA.

in this case,cells which don't have DNA, use RNA as DNA in the cell which has it. but there is no reason for us to said that at a cell which has DNA and RNA both of them have the same power to control the activities of cell. at other word,DNA is more dominant.
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Postby victor » Thu Sep 08, 2005 11:31 am

Canalon wrote:This is a very simplified version of what can happen. Search Medline for DNA repair, you will see it is a very complicated thing :)
Patrick


Even the simplified version looks complicated for me.. :lol:

@Baikuza
You can say it. DNA is more dominant since it replaces RNA in the nucleus to cytoplasm because DNA is much more complex and stable than RNA.
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