From The Scientist :
A large number of human genes can substitute for their defective counterparts in yeast and prevent the microorganisms from dying, according to a paper published today (May 21) in Science. Of more than 400 human-to-yeast gene replacements performed, almost 50 percent were effective at compensating for a missing vital function.
“No one has carried out an evolutionary study of this kind before and certainly not of this scale,” said Nevan Krogan of the University of California, San Francisco, who was not involved in the work. “It’s rather satisfying to see that half of the genes could complement [the yeast function] because it justifies continuing working in yeast as a model . . . to help understand human genes.”
In short, Darwin was wrong. Species do not just continue to diverge, via natural selection acting on random mutation.
It appears that if a process as a whole has diverged between yeast and humans, then its proteins “have all changed together,” said Madan Babu of the Medical Research Council Laboratory of Molecular Biology in the U.K., who was not involved in the work. “If you can’t replace some of the subunits of the DNA repair machinery, then you can’t replace any of them.”
There has got to be a better model for the genome than the one that the tenured Darwin profs have stuck us with.
Abstract: To determine whether genes retain ancestral functions over a billion years of evolution and to identify principles of deep evolutionary divergence, we replaced 414 essential yeast genes with their human orthologs, assaying for complementation of lethal growth defects upon loss of the yeast genes. Nearly half (47%) of the yeast genes could be successfully humanized. Sequence similarity and expression only partly predicted replaceability. Instead, replaceability depended strongly on gene modules: Genes in the same process tended to be similarly replaceable (e.g., sterol biosynthesis) or not (e.g., DNA replication initiation). Simulations confirmed that selection for specific function can maintain replaceability despite extensive sequence divergence. Critical ancestral functions of many essential genes are thus retained in a pathway-specific manner, resilient to drift in sequences, splicing, and protein interfaces. (paywall) – A.H. Kachroo et al., “Systematic humanization of yeast genes reveals conserved functions and genetic modularity,” Science, 348:921-25, 2015.
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