Why not DNA to protein directly?

[Helix]

Hi, Could anybody explain why is it DNA to RNA to Protein , but not DNA to Protein directly?

Thanks

[herb386]

There are probably quite a few reasons but here are a few that I can think of:

RNA probably existed long before proteins so the natural progression of evolution would have been from RNA to protein. Loosing the RNA step would be very difficult.

By producing RNA and then using each RNA molecule many times to produce protein you get an amplification step which speeds up protein production.

It provides an extra control step in gene expression.

RNA is single stranded so you can easily read it's sequence. If you wanted to get DNA through a ribosome you would have to separate the two strands to a large distance which opens it to attack from mutagens.

Getting a ribosome to a specific point on a chromosome would be very hard because of the size of molecules involved. RNA is small in comparison so can move easily to the ribosome.

In bacteria it is the end of the RNA that defines the start site for translation (I think) and so translation of genes in the middle of a large DNA molecule would require all the genes before it to be translated.

There are probably more reasons but that's all I can think of at the moment. Hope it's helpful.

[Helix]

Thank you very much!! yes it is indeed a great help as answers for this type of questions are rather difficult to find from the text books.

Thanks a lot again

Regards
Helix

[Segnar]

yes, i think so... :)

[kiekyon]

also, recent research found that RNA imolecules are not merely passive conduit through which the gene's message flow, but rather active regulator of cellular processes.
hence it is necessary for protein translation to occur through RNA

[victor]

also, recent research found that RNA imolecules are not merely passive

Yupz...and that's the invention of ribozyme.. it's a cool name actually..

[qq-wheat]

dna have helix,rna not.

[biorad]

Also, in eukaryotic systems, the coding regions of DNA are separated by large noncoding regions ("dummy code", probably to protect the coding regions). If we were to go directly from DNA to proteins, we would get huge, completely functionless proteins. Only through transcription and splicing can we produce the proteins necessary to sustain life.