Horizontal gene transfer or lateral gene transfer: In some organisms like bacteria, variation may result from horizontal gene transfer.

Horizontal gene transfer or lateral gene transfer:

In some organisms like bacteria, variation may result from horizontal gene transfer. This is a 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, its parent or a species from which it evolved. Horizontal gene transfer is a significant phenomenon. Artificial horizontal gene transfer is a form of genetic engineering.

The phenomenon appears to have had some significance for unicellular eukaryotes as well. There is some evidence that even higher plants and animals have been affected. Horizontal gene transfer is common among bacteria, even very distantly related ones.

This process is thought to be a significant cause of increased drug resistance, when one bacterial cell acquires resistance, it can quickly transfer the resistance genes to many species.

There are majorly three processes for horizontal gene transfer in bacteria, transduction, transformation and conjugation. Horizontal gene transfer is a potential confounding factor in inferring phylogenetic tress based on the sequence of one gene. For example, given two distantly related bacteria that have exchanged a gene, a phylogenetic tree including those species will show them to be closely related because that gene is the same, even though most other genes have substantially diverged.