Solution :

Microinjection, Electroporation and Gene gun methods are the three vectorless methods of introducing rDNA into a competent host cell.

Microinjection: It is the process of introducing foreign DNA into the host cell by injecting DNA directly into the nucleus by using micro needles or micro pipettes

Electroporation: It is the process by which transient holes are created in the plasma membrane of the host cell to facilitate the entry of foreign DNA.

Gene gun: It is the technique of bombarding micro projectiles coated with foreign DNA with great velocity into the target cell.

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