The cells of the human body contain about 145 genes derived from bacteria, other unicellular organisms, and viruses. A new study, published in the journal Genome Biology, has provided ample evidence that, as they evolve, genes from other life forms enter animal cells. The article is summarized by Science News.
Horizontal gene transfer (transfer of information to another organism that is not its descendant) is common among bacteria and other unicellular organisms. This makes it easier for organisms to acquire resistance to antibiotics by taking a set of genes encoding this property. However, not everyone believed in the ability of foreign genes to enter the cells of higher animals.
Alastair Crisp of Cambridge and his colleagues analyzed the genomes of 40 animal species, from fruit flies and zebrafish to gorillas and humans. For each gene, scientists searched databases for similar genes of both animals and more primitive life forms (plants, fungi, bacteria, and viruses). Whenever a gene was closer to the latter, scientists looked at it in more detail.
In total, the researchers found hundreds of genes that seem to have entered the body of animals from other kingdoms of wildlife. In humans, there were 145 such genes.
These genes have long been ingrained and play stable roles in metabolism, immune responses, and basic biochemical processes. However, understanding how and when these genes got from primitive creatures to humans will require a separate study.
However, not all biologists were convinced by Crisp's findings. The presence of similar genes in organisms that are far from each other can be explained not only by horizontal transfer, but also by the accidental preservation of the heritage received from an unknown distant ancestor, according to Jonathan Eisen of the University of California at Davis.
