Comparison between the Two Gene Scissors: the Third-Generation CRISPR-Cas9 Technique and the Base Ed (image) Institute for Basic Science Share Print E-Mail Caption In the original CRISPR-Cas9 technique (top), the guide RNA (green) binds to the target DNA and the cleavage enzyme Cas9 (scissors) cuts out a small DNA sequence (red). A modified version of Cas9 called nCas9 (bottom) is different as it cuts off only one strand of DNA and the cytidine deaminase (pink) transforms a single cytosine (C) into uracil (U). Uracil (U) is then converted to thymine (T) by DNA replication. Credit IBS Usage Restrictions None Share Print E-Mail 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.