Horizontal Gene Transfer

Horizontal gene transfer (HGT), also Lateral gene transfer (LGT), is any process in which an organism transfers genetic material to another cell that is not its offspring. By contrast, vertical transfer occurs when an organism receives genetic material from its ancestor, e.g. its parent or a species from which it evolved. Most thinking in genetics has focused on the more prevalent vertical transfer, but there is a recent awareness that horizontal gene transfer is a significant phenomenon.

There is some evidence that even higher plants and animals have been affected. Dr. Mae-Wan Ho, a noted scientist and critic of genetic engineering, writes: "While horizontal gene transfer is well-known among bacteria, it is only within the past 10 years that its occurrence has become recognized among higher plants and animals. The scope for horizontal gene transfer is essentially the entire biosphere, with bacteria and viruses serving both as intermediaries for gene trafficking and as reservoirs for gene multiplication and recombination (the process of making new combinations of genetic material)." But Richardson and Palmer (2007) are more cautious: "Horizontal gene transfer (HGT) has played a major role in bacterial evolution and is fairly common in certain unicellular eukaryotes. However, the prevalence and importance of HGT in the evolution of multicellular eukaryotes remain unclear.

Due to the increasing amount of evidence suggesting the importance of these phenomena for evolution (see below), molecular biologists such as Peter Gogarten have described horizontal gene transfer as a "A New Paradigm for Biology".

It should also be noted that the process is emphasised by Dr. Mae-Wan Ho as an important factor in "The Hidden Hazards of Genetic Engineering", as it may allow dangerous transgenic DNA (which is optimised for transfer) to spread from species to species.