Which of the following are NOT used in the production of chimeras?

• A. Blastocysts
• B. Pseudopregnant females
• C. Superovulated females
• D. Unfertilized eggs

Answer: (D)

Chimera production relies on using fertilized embryos at the blastocyst stage and introducing donor material into them, then transferring those embryos into a recipient that can support development. Unfertilized eggs don’t contain a nucleus with genetic material to contribute to a chimera, so they cannot form chimeras. Blastocysts are the stage used as the host for integrating donor cells or for embryo aggregation. Pseudopregnant females provide the proper uterine environment for embryo implantation and development when there isn’t a pregnancy yet. Superovulated females yield more embryos, boosting the number of potential chimeras you can produce. Because of this, unfertilized eggs are not used in chimera production.