What is the name of the technique for injecting DNA directly into the fertilized egg with a tiny glass pipette?

• A. Intraembryonic injection
• B. Retroviral insertion
• C. Embryonic stem cell insertion
• D. Pronuclear injection

Answer: (D)

Pronuclear injection is the technique of injecting DNA directly into the fertilized egg’s pronucleus using a microinjection pipette. Doing this at the zygote stage lets the introduced DNA be incorporated into the genome as the embryo divides, so the resulting offspring can carry the foreign gene in the germline. This method is used to create transgenic animals by delivering DNA before the genome begins extensive replication. It differs from retroviral insertion, which uses viral vectors to carry DNA into cells; embryonic stem cell insertion, where DNA is introduced into cultured ES cells and then used to generate chimeras; and intraembryonic injection, which targets later-stage embryos rather than the one-cell zygote.