Thursday, August 10, 2006

Did sex start as DNA takeovers?

I wonder what would lead a cell to exchange its DNA/RNA/or any other kind of genetic material with another cell.

The process through which unicellular organisms become more complex ones is acceptable up to a certain level if we consider the hypothesis that the somatic cells are indeed slaves of the original reproductive cells (named reproductive because they can generate other non-specialized fully functional cells and not because they´re cells specialized in reproduction as germ line cells) but how could the "modern" mechanisms of sex be created?

Bacteria are capable of exchanging genetic material through conjugation, the individuals that have a plasmid named F factor are capable of inserting this genetic material into bacteria of the same species that do not have the F factor. It is supposed that this mechanism can be a way of transmitting resistance against pathogens or drugs such as antibiotics.

Here I propose another interpretation, I believe that a good reason for a cell to be willing to insert its genetic data into another one is in fact an attempt to hijack the host cell and use its inner machinery to work for the original cell and its genome.

If this mechanism becomes widespread, these invasions could end up by happenning simultaneously and thus giving the ilusion that there´s a mutually consented sexual intercourse happenning.

In order to avoid multiple invasions (what could lead to an invasion of the original cell itself) some sort of mechanism must have been put in place and so the genome multiplicity might have reached an equilibrium : the cells split themselves before attempting an invasion and thus reduce their genetic content into half, leading to two individuals with the same genome size as the original ones but with a different set of genes.

At this point the invasion strategy no longer provides advantage to the cells capable of doing so but now a new advantage appears for the individuals that are capable of exchanging their genetic material are now more resistant to pathogens and their "evolution" can happen faster for all the reasons that are attributed to modern sex.