Recombination in primeval genomes: A step forward but still a long leap from maintaining a sizable genome

Abstract

A stubborn question in early molecular evolution is how to sustain the "minimum" informational length required for the basic features of life with a putative low-copying fidelity RNA polymerase ribozyme. Proposals to circumvent the information crisis have primarily focused on networks of cooperative molecules or compartmentalization of noncooperative unlinked templates, but success has been very limited so far. Lehman (2003) has recently suggested that recombination-a frequently ignored player in early evolution-could have been crucial to building up primeval genomes of sizable length. Here we investigate this claim by assuming (without loss of generality) that genes were already enclosed in a compartment (vesicle, protocell). The numerical results show a quite intricate interplay among mutation, recombination, and gene redundancy. Provided that the minimum number of gene copies per protocell was enough for recombination to recreate wildtype templates-but not too high to impose an unbearable burden of mutants informational content could have increased by at least 25% by keeping the same mutational load as that for a population without recombination. However, the upper bound of informational length would still be far from the "minimal life" provisions.