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Nat Rev Microbiol. 2003 Nov;1(2):127-36.

Comparative genomics, minimal gene-sets and the last universal common ancestor.

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National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, NIH Building 38A, 8600 Rockville Pike, Bethesda, Maryland 20894, USA.


Comparative genomics, using computational and experimental methods, enables the identification of a minimal set of genes that is necessary and sufficient for sustaining a functional cell. For most essential cellular functions, two or more unrelated or distantly related proteins have evolved; only about 60 proteins, primarily those involved in translation, are common to all cellular life. The reconstruction of ancestral life-forms is based on the principle of evolutionary parsimony, but the size and composition of the reconstructed ancestral gene-repertoires depend on relative rates of gene loss and horizontal gene-transfer. The present estimate suggests a simple last universal common ancestor with only 500-600 genes.

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