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Author Topic:   Manipulation of DNA by cells?
Taq
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Posts: 7592
Joined: 03-06-2009
Member Rating: 3.4


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Message 31 of 36 (671027)
08-21-2012 5:18 PM
Reply to: Message 30 by zi ko
08-21-2012 3:52 PM


Re: Meaningless controversy
Fortunatly during last years it became more than evident, that environment forwards to genome information that plays substantial role in life evolution.

Not at all. Ever since we first discovered the molecular mechanisms involved with DNA (early 1960's?) we have understood that the gene pool of a population changes through time due to the transfer of information produced by selection. It is selection that produces the information we see in genomes today.

The real and critical question lies here: is this information, arriving from natural laws, able to give the answers needed to explain life appearance and then life evolution? Or something more is needed?

Evolution? Absolutely yes. The information in genomes is a direct record of past evolutionary events.

Origin of life? Very difficult to say. I think only the broadest strokes can be pulled from modern genomes. For example, we can see a central role for RNA in modern life. It acts in many different roles, from gene regulator to producer of proteins to enzyme. I think this is strong evidence that RNA was the primary player in the first life. RNA can act in all of the roles that are necessary for life, from inheritance to enzymatic reactions.

Edited by Taq, : No reason given.


This message is a reply to:
 Message 30 by zi ko, posted 08-21-2012 3:52 PM zi ko has responded

Replies to this message:
 Message 32 by zi ko, posted 08-22-2012 9:35 AM Taq has responded
 Message 34 by herebedragons, posted 08-22-2012 10:33 AM Taq has responded

  
zi ko
Member (Idle past 1568 days)
Posts: 578
Joined: 01-18-2011


Message 32 of 36 (671092)
08-22-2012 9:35 AM
Reply to: Message 31 by Taq
08-21-2012 5:18 PM


Re: Meaningless controversy
... we can see a central role for RNA in modern life. It acts in many different roles, from gene regulator to producer of proteins to enzyme. I think this is strong evidence that RNA was the primary player in the first life. RNA can act in all of the roles that are necessary for life, from inheritance to enzymatic reactions.

Very intersting. Could RNA role be thought as something like epigenetics, though far more reaching, extented an deeper mechanism?

'If that much-spoken 'evidence" of followers of random mutations is this 'some evidence' of Panda, then there is a serious matter of credibility in this forum.

This message is a reply to:
 Message 31 by Taq, posted 08-21-2012 5:18 PM Taq has responded

Replies to this message:
 Message 33 by Taq, posted 08-22-2012 10:18 AM zi ko has responded

    
Taq
Member
Posts: 7592
Joined: 03-06-2009
Member Rating: 3.4


(1)
Message 33 of 36 (671099)
08-22-2012 10:18 AM
Reply to: Message 32 by zi ko
08-22-2012 9:35 AM


Re: Meaningless controversy
Very intersting. Could RNA role be thought as something like epigenetics, though far more reaching, extented an deeper mechanism?

I don't think so. RNA is short lived in the cell and are regularly degraded through different mechanisms. I really don't see a role for different RNA's in inheritance. In the short term, RNA could definitely regulate gene expression. However, DNA is still the molecule responsible for inheritance in modern organisms. You need to change the DNA sequence to get meaningful evolutionary change.

Edited by Taq, : No reason given.


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 Message 32 by zi ko, posted 08-22-2012 9:35 AM zi ko has responded

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herebedragons
Member
Posts: 1483
From: Michigan
Joined: 11-22-2009


(1)
Message 34 of 36 (671103)
08-22-2012 10:33 AM
Reply to: Message 31 by Taq
08-21-2012 5:18 PM


RNA world hypothesis
Origin of life? Very difficult to say. I think only the broadest strokes can be pulled from modern genomes. For example, we can see a central role for RNA in modern life. It acts in many different roles, from gene regulator to producer of proteins to enzyme. I think this is strong evidence that RNA was the primary player in the first life. RNA can act in all of the roles that are necessary for life, from inheritance to enzymatic reactions.

RNA is much less stable than DNA and is prone to hydrolysis. Stable, functional RNA units are usually associated with proteins and involve complex folding patterns as contrasted to DNA structures. Use of RNA as the main storage unit would not be impossible but rather energy intensive, not particularly conducive to early life with lower energy resources (assuming photosynthesis, mitochondria, electron transport and such were not in existence yet)

RNA is not known to self replicate in nature (at least as far as I know) and is instead transcribed from DNA. I know they have created self-replicating RNA in the lab which does suggest that RNA could self-replicate. But in nature, even viruses need a DNA host in order to replicate. RNA also has the base Uracil rather than Thymine which makes it more subject to mispairings than DNA (which could be a good thing or a bad thing for early life).

As far as the role RNA plays in modern organisms ... without DNA regulation of these processes it is only speculation of what RNA's role would be in early life. It shows that RNA can perform these functions and certainly does play a central role in modern life, but it is unclear that RNA could perform these functions without DNA regulation.

I know you are aware of all these things, you are not arguing from ignorance. So I wonder how you consider that there is "strong evidence" that RNA was the primary player in early life? At best I think you could say "conceptually possible".

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for. But until the end of the present exile has come and terminated this our imperfection by which "we know in part," I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

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 Message 31 by Taq, posted 08-21-2012 5:18 PM Taq has responded

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Taq
Member
Posts: 7592
Joined: 03-06-2009
Member Rating: 3.4


(1)
Message 35 of 36 (671111)
08-22-2012 10:56 AM
Reply to: Message 34 by herebedragons
08-22-2012 10:33 AM


Re: RNA world hypothesis
RNA is much less stable than DNA and is prone to hydrolysis. Stable, functional RNA units are usually associated with proteins and involve complex folding patterns as contrasted to DNA structures. Use of RNA as the main storage unit would not be impossible but rather energy intensive, not particularly conducive to early life with lower energy resources (assuming photosynthesis, mitochondria, electron transport and such were not in existence yet)

It is also worth mentioning that RNA's instability in the modern cell is due to RNA degrading enzymes. Given the right environment, RNA can be relatively stable. A reducing environment would obviously be best, and that is what we have in the early Earth. I fully agree that DNA is more stable than RNA.

RNA is not known to self replicate in nature (at least as far as I know) and is instead transcribed from DNA.

That depends on how you look at it. There is not a strict hierarchy in the cell. Does DNA make DNA? No. Proteins make DNA in combination with RNA primers, and it is ribosomal RNA's and tRNA's that make proteins from mRNA's. DNA could be looked at as just a more stable form of RNA that is stored for future use.

As far as the role RNA plays in modern organisms ... without DNA regulation of these processes it is only speculation of what RNA's role would be in early life. It shows that RNA can perform these functions and certainly does play a central role in modern life, but it is unclear that RNA could perform these functions without DNA regulation.

It is RNA and proteins made by RNA that controls gene expression. I would also suspect that RNA's can interact and control their own activity just as proteins can.

Of course, I am make very strong statements here that do breakdown a bit when scrutinize, but I do think that the major themes are there. RNA still plays a central role in the cell. It could be argued that we still live in an RNA World.


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zi ko
Member (Idle past 1568 days)
Posts: 578
Joined: 01-18-2011


Message 36 of 36 (671195)
08-22-2012 10:03 PM
Reply to: Message 33 by Taq
08-22-2012 10:18 AM


Re: Meaningless controversy
"I really don't see a role for different RNA's in inheritance."

"I think this is strong evidence that RNA was the primary player in the first life. RNA can act in all of the roles that are necessary for life, from inheritance to enzymatic reactions."


Aren't these two statements contradictory?

Edited by zi ko, : No reason given.


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 Message 33 by Taq, posted 08-22-2012 10:18 AM Taq has not yet responded

    
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