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Author Topic:   Origin of viruses
Dr Jack
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Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


(2)
Message 5 of 24 (670762)
08-18-2012 6:17 PM
Reply to: Message 1 by Kiddo
08-18-2012 2:20 PM


No-one knows, nor is it clear that they share a common origin. There is some reason to believe some viruses predate cellular life but since viruses leave no fossils we have no direct evidence to work with.

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 Message 7 by RAZD, posted 08-19-2012 12:02 AM Dr Jack has replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


(1)
Message 8 of 24 (670785)
08-19-2012 4:33 AM
Reply to: Message 7 by RAZD
08-19-2012 12:02 AM


Re: RNA world
Hi RAZD,
I'm going by Koonin et al (2006) The ancient Virus World and evolution of cells (open access). Which states:
quote:
Comparative genomics provides no evidence of a monophyletic origin of all viruses. Many virus groups simply share no common genes, effectively, ruling out any conventional notion of common origin. ... For example, most of the viruses of hyperthermophilic crenarchaea have literally no genes in common with any other viruses, whereas RNA viruses share with DNA viruses and plasmids that replicate via the rolling circle mechanism only extremely distant domains in their respective replication proteins.
Which leaves us with genetic evidence and (informed?) speculation.
Absolutely, but let's not confuse coherent hypothesis with directly evidenced theory.

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 Message 7 by RAZD, posted 08-19-2012 12:02 AM RAZD has replied

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 Message 9 by RAZD, posted 08-19-2012 5:19 AM Dr Jack has replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


(1)
Message 10 of 24 (670787)
08-19-2012 5:38 AM
Reply to: Message 9 by RAZD
08-19-2012 5:19 AM


Re: RNA world
Hi RAZD,
btw -- do you know if viruses have ever been responsible for beneficial gene sequences? or do we only get deleterious and then neutralized ones.
Yes. Genes vital for placental formation are derived from retroviruses. Hang on, I'll dig out a source...
Black et al (2010) Endogenous Retroviruses in Trophoblast Differentiation and Placental Development
Edited by Mr Jack, : Added reference

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


Message 22 of 24 (671226)
08-23-2012 11:15 AM
Reply to: Message 20 by Kiddo
08-22-2012 9:20 PM


all other organisms tend to increase their functionality/complexity , like secreting enzymes, developing protective coats around them, etc. But in case of viruses, they became more simpler and lost their functions rather than gaining new ones.
Viruses are developing new functions all the time. They're extremely refined replicators with some of the most remarkable adaptations.

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