How can a gene gun insert a gene into an organism?

The gene gun method or biolistic particle delivery system is used in biotechnology for genetically modifying plants.

With the use of a gene gun, the gene gun method delivers vector DNA or plasmid directly into a host plant’s nucleus. The payload is an elemental particle of a heavy metal coated with DNA. The method is also commonly called particle acceleration or microprojectile bombardment.

The gene gun can be used on seedlings or tissue culture cells. Prior to injecting the DNA into the plant tissue via the gene gun, either microscopic gold or tungsten particles are liberally coated with many hundreds of copies of genes. The particles are then forced into the nucleus with the gene gun.

Gene gun is a syringe type equipment to put DNA into the cytoplasm of a cell. It 'shoots' a nanoparticle coated with DNA into the cell. Once inside the cytoplasm, the DNA integrates randomly with the host chromosome by mechansims like recombination.