Chimeric mice are generated by injecting targeted mES cells into blastocyst stage embryos which are then transferred in pseudopregnant females to develop to term. Mouse strain routinely used as blastocyst donor is C57Bl/6N. However, other mouse strains are also available.Other method for producing chimeric mice is morula aggregation, which is available upon demand. The degree of chimerism of the progeny generated is evaluated based on coat color or PCR.The best chimeric males are bred with C57BL/6 mice in order to transmit the knockout allele through the mouse germline. Genotyping samples are taken for PCR or Southern blot to identify mice that are heterozygous for the knockout allele.Blastocyst injection service includes injection and transfer of approximately 60 blastocysts. We also provide service in following steps of chimera breeding.

Tetraploid Aggregation

TCDM has the expertise for tetraploid ES cell aggregation that is used to generate embryos that are completely ES cell derived. With the technique one can e.g. rescue an embryonic lethal phenotype caused by a placenta defect.

Petra Sipilä, PhD
Adjunct Professor of Reproductive and Developmental Biology

Email: petra.sipila(at)

Chimeric Mouse Production
Blastocyst injections, morula and tertaploid aggregation