What is "horizontal gene transfer"

n. (context genetics English) The transfer of genetic material from one organism to another one that is not its offspring; especially common among bacteria.

Horizontal gene transfer (HGT) is the movement of genetic material between unicellular and/or multicellular organisms other than via vertical transmission (the transmission of DNA from parent to offspring.) HGT is synonymous with lateral gene transfer (LGT) and the terms are interchangeable. HGT has been shown to be an important factor in the evolution of many organisms.

Horizontal gene transfer is the primary reason for the spread of antibiotic resistance in bacteria and plays an important role in the evolution of bacteria that can degrade novel compounds such as human-created pesticides and in the evolution, maintenance, and transmission of virulence. This horizontal gene transfer often involves temperate bacteriophages and plasmids. Genes that are responsible for antibiotic resistance in one species of bacteria can be transferred to another species of bacteria through various mechanisms (e.g., via F- pilus), subsequently arming the antibiotic resistant genes' recipient against antibiotics, which is becoming a medical challenge to deal with.

Most thinking in genetics has focused upon vertical transfer, but there is a growing awareness that horizontal gene transfer is a highly significant phenomenon and among single-celled organisms, perhaps the dominant form of genetic transfer.

Artificial horizontal gene transfer is a form of genetic engineering.