In pronuclear injection, why are some females mated to vasectomized males?

• A. To produce more eggs
• B. To induce pseudopregnancy
• C. To increase the probability that the transgene will be incorporated in the cells
• D. To provide sperm for fertilizing the ova

Answer: (B)

Mating to a vasectomized male is used to induce pseudopregnancy, creating a uterus that is physiologically ready to accept and support implanted embryos. The act of mating triggers hormonal changes, especially progesterone from the corpora lutea, that mimic the early pregnancy state even though no fertilization occurs. This “pregnancy-like” environment is crucial for embryo transfer after pronuclear injection, helping the transplanted embryos implant and develop. It’s not about making more eggs, influencing how the transgene integrates, or providing sperm—those aren’t achieved by this step. The goal is to prepare the recipient uterus for successful implantation and development of the injected embryos.