Humans and baker’s yeast, Saccharomyces cerevisiae, last shared an ancestor 1 billion years ago. Despite the evolutionary gulf, human genes can substitute for nearly half — 47 percent — of the genes essential for yeast survival, researchers report in the May 22 Science.
Aashiq Kachroo and colleagues at the University of Texas at Austin replaced each of 414 genes in yeast with a human version. Genes with certain functions, such as those involved in metabolizing lipids, could be swapped about 90 percent of the time. But very few yeast genes involved in cell growth and death could be replaced with their human counterparts. Processes with more replaceable genes have been preserved throughout evolution, while those with fewer swappable genes have developed species-specific innovations.