Trans-activating CRISPR RNA (tracrRNA)

Abbreviation for trans-activating CRISPR RNA, pronounced “tracer RNA.” In the CRISPR-Cas9 system, the tracrRNA base pairs with the crRNA to form a functional guide RNA (gRNA). Cas9 uses the tracrRNA portion of the guide as a handle, while the crRNA spacer sequence directs the complex to a matching viral sequence.