Tuesday, May 15, 2007

The Significance of Minimal Genome Concepts

'How many genes can make a cell: the minimal-gene-set concept' contains an abstract; a part of which follows. The abstract in full is linked.

"Several theoretical and experimental studies have endeavored to derive the minimal set of genes that are necessary and sufficient to sustain a functioning cell under ideal conditions, that is, in the presence of unlimited amounts of all essential nutrients and in the absence of any adverse factors, including competition. A comparison of the first two completed bacterial genomes, those of the parasites Haemophilus influenzae and Mycoplasma genitalium, produced a version of the minimal gene set consisting of approximately 250 genes. Very similar estimates were obtained by analyzing viable gene knockouts in Bacillus subtilis, M. genitalium, and Mycoplasma pneumoniae. With the accumulation and comparison of multiple complete genome sequences, it became clear that only approximately 80 genes of the 250 in the original minimal gene set are represented by orthologs in all life forms."

Despite multiple research projects, involving separate organisms, indicating minimal genome sizes that range up to several hundred genes, mainstream origin of life advocates have been scarcely influenced by implications derived from their results. OOLers continue to believe that pathways are amenable to paradigms envisioning continuous, small incremental changes. In my view the results of minimal genome studies lend strong support to a natural barrier concept. A minimal level of function, requiring a higher level of complexity than can be attained through continuous slight increments, fits a barrier model.

The response of OOLers is to claim that a precursor cell would have had different properties enabling a simpler replicating entity. Claims are easily made but where's the empircal evidence to back this one up?



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