Mice (IMAGE) The Francis Crick Institute Caption The black coat of the mouse refers to the genetically modified cells, the white is the non-modified cells. The researchers breed these animals to produce offspring which are 100% genetically modified, containing one half of CRISPR-Cas9. Credit The Francis Crick Institute Usage Restrictions With credit License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.