Germline Testing of Chimera

Coat color is a powerful and cost-effective marker for mutagenesis at the Mouse Biology Program, offering a visually distinct and reliable method to track and monitor genetic changes in mouse models, ensuring accurate and efficient research outcomes.


Chimeras are produced by injecting clonal mutant embryonic stem (ES) cells into donor blastocysts (or morula), resulting in offspring that contain a mix of mutant and wild-type cells. At the Mouse Biology Program, we carefully assess chimeras for coat color at ten days of age, as coat color provides an early indicator of germline transmission potential.

Key steps in our chimera process include:

  • Coat Color Assessment: Chimeras with 50% or more of their coat color derived from mutant cells are highly likely to contribute mutant cells to the germline. This visual marker helps predict the potential success of downstream breeding efforts.
  • Breeding Strategy: Male chimeras with 50% or more outstanding mutant cell contribution are paired with females starting at 7 to 9 weeks of age, a critical step in maximizing the chances of germline transmission.
  • Germline Transmission (GLT) Breeding: Each male chimera is paired with females of the appropriate genetic background whenever possible. This targeted approach optimizes the chances of successful germline transmission, facilitating the efficient propagation of mutant alleles.

With our rigorous assessment and breeding strategies, researchers can confidently advance their projects, knowing that our methods ensure efficient, reliable transmission of mutant alleles to support diverse scientific investigations.