Think that you and a humble yeast culture have nothing in common? Think again; humans and a loaf of bread have a common ancestor, and we share hundreds of genes that haven't changed all that much in a billion years.
So despite diverging evolution over a billion years, genes from that last common ancestor are still present in both humans and yeast, researchers say.
To test that commonality, the researchers inserted more than 400 human genes into yeast cells, reporting in the journal Science that almost half of them remained functional and helped the yeast to survive.
They engineered hundreds of new yeast strains, each with a single different human gene inserted in place of a gene critical for yeast's survival, to see which strains could live and reproduce.
"Cells use a common set of parts and those parts, even after a billion years of independent evolution, are swappable," says study leader Edward Marcotte, a biologist at The University of Texas at Austin.
"It's a beautiful demonstration of the common heritage of all living things - to be able to take DNA from a human and replace the matching DNA in a yeast cell and have it successfully support the life of the cell."
There could be applications of the study findings for human health, the researchers point out, perhaps offering new ways to test for human diseases linked to genetic mutations.
Particular versions of a mutated human gene could be inserted into yeast that could be exposed to a variety of drugs to test possible new treatments, they say.
There may be as many as 1,000 pairs of swappable genes that could be useful in identifying drugs as therapies for a number of human genetic diseases, they estimate.
"We could find out if one of the standard treatments would work on your particular version of the gene or if maybe another drug would be even better," says study co-author Claus Wilke of the university's Department of Integrative Biology.
The best predictor of whether a human and yeast gene could be swapped wasn't how closely the genetic sequences matched but rather what module - a group of many genes working together to regulate some cellular process - they were a part of, the biologists found.
"This work is basically showing that you can take a fuel injector from a tractor and swap it for a fuel injector in your Toyota and it will still work, more or less, because they're both fuel injectors," says Marcotte.