What is horizontal gene transfer

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Exchange of genetic material between different living beings.

In genetic engineering, the transfer of individual genes from a donor to a recipient organism is known as gene transfer.

A distinction is made between vertical and horizontal gene transfer.

Horizontal gene transfer
Horizontal gene transfer is the transfer or ingestion of genetic material outside the sexual reproductive pathways and independent of existing species boundaries. Depending on certain conditions, a horizontal gene transfer - for example from a plant to a soil bacterium - is basically possible, but a very unlikely event under natural conditions.

When assessing the safety of genetically modified plants, the possibility of a foreign gene being passed on via horizontal gene transfer should be taken into account - regardless of the likelihood of occurrence. For example, antibiotic resistance genes used as marker genes could be passed on from a transgenic plant to soil or intestinal bacteria.

Vertical gene transfer (crossing)
If two plants cross sexually and pass their genes on to the following generations, this process is a vertical gene transfer, usually referred to as crossing.

By crossing transgenic with non-transgenic crop plants, the latter also take up the introduced gene constructs. When assessing the safety of transgenic plants, the possibility of outcrossing the foreign gene into closely related wild plant species is therefore an important aspect.