Problems with Chromosomal Evolution - From Circular to Linear

Harking back to a previous thread concerning early life (about the origin of viruses):What if the origin of the nucleus is a complex viral genome that got 'stuck' in a primitive archaea? That way, a linear genome (in the early pool of proto-cells) could be replaced by a circular one (in Archaea and Bacteria), which in turn got usurped by a more stable linear model (to produce an early eukaryote).This is a paper suggesting just that (I think, I can't get access to the full text).I don't know if the article is much cop, because I can't read the full text and its's only a 'comment' or 'letter'. I also have no idea whether it has been laughed at by all and sundry since then, but here's a snippet from the abstract:

quote:

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It is proposed that several characteristic features of the eukaryotic nucleus derive from its viral ancestry. These include mRNA capping, linear chromosomes, and separation of transcription from translation.

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Any thoughts?

I realise that it does nothing to really tackle the main point of the OP, but I do think it changes the nature of the challenge slightly. If the nucleus evolved from a parasitic or symbiotic organism that had a linear chromosome (in other words never made the transition to circular) then the chain of events stops being:Linear => Circular => Linear (which seems like a wierd way of going about things)toLinear => Circular and LinearParasitic organisms would get around the problem of chromosome stabilisation by replicating like mad and using the host to keep their genomes relatively small, whilst others developed circular chromsomes to become all-singing all-dancing biochemical factories. It removes the absolute requirement for telomeres to survive, and presents the possiblity that parts of the hosts genome could be co-opted by the parasitic DNA to stabilise the ends of the relatively unstable linear chromosome (I think this is what Loudmouth was saying).As for what the abstract said about the chain of events, I think I could sum it up like this:

• The virus (or similar parasite) has a mechanism to trick the host cell into engulfing it.
• The parasite then gets 'stuck' inside the host cell and a sort of symbiosis exists with a circular genome knocking around in the cytosol and a proto-nucleus.
• The mechanism for engulfing things would still be active and the ability to prey on smaller cells would reduce the need for the first eukaryotes to make a lot of nutrients themselves.
• As the genes in the circular chromosome would be less needed it would be easy to imagine a situation where important genes are sequestered by the nucleus and the rest of the 'host' geneome is lost completely.

This cell-turned-predator idea would also explain the advent of mitochondria and chloroplasts (but that is Off-topic)Concerning the new topic suggestion: I certainly like the idea of a thread entitled 'All men are parasites' (or similar), but I'm afraid I don't know too much about the evolution of sex so I might have to do a bit of digging or turn it into more of an enquiry type of topic - unless you want to have a shot at it of course.