So from what I understand, in gene editing, the CRISPR vector expresses a small RNA sequence comprised of a small guide-RNA that is complementary to your target sequence. The sgRNA comprises a 20 Bp CrRNA and a truncated (cut down) TracrRNA right ?

My main question is how does this truncation enable gene editing ? After all, the bacteria have a full TracrRNA and not a truncated one.


1 Answer 1


You are correct about the components of the sgRNA.

However the truncation of the tracrRNA does not enable gene editing. Rather it is all that is required.

In bacteria the crRNA and tracrRNA are distinct molecules which must pair through the complementary palindromic repeat sequences. This is not the case in gene-editing as the crRNA and tracrRNA have been fused with a synthetic stem loop. Thus the palindromic repeat sequence is not required and the tracrRNA is shorter.

Check out Cong et al. (2013) in Science.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .