One way of physically introducing DNA into a cell is microinjection. Under a microscope , a cell is manipulated to a blunt capillary.
Gentle suction holds the cell in place.
With a micromanipulator , a very fine tipped pipet is inserted into the cytoplasm or nucleus. DNA or RNA is injected directly into the nucleus or cytoplasm. Microinjection has been successfully used with large frog eggs, cultured mammalian cells, mammalian embryos, and plant protoplasts and tissues. Microinjection of fertilized mammalian eggs with genes is a major route for the production of transgenic animals . The ethics of the production of transgenic organisms is a subject of vigorous public debate .