CRISPR

CRISPR (Clustered regularly interspaced short palindromic repeats) are segments of naturally-occurring prokaryotic DNA containing short, repetitive base sequences. These segments are sequences in the DNA of bacteria are copied from invading plasmids and phages, saved in the bacteria's own DNA in a library-like fashion and provide the bacteria with an immune system as a form of acquired immunity. The protein Cas uses the copied DNA sequences to attack later invading DNA from the same invading species to cut the invading DNA. The DNA copy is translated into RNA. The resulting RNA molecule is complexed with the Cas molecule and it guides the complex to the target invading DNA, where the Cas molecule cuts the matching invading DNA at a precise point.

In 2013, Cas9 was complexed with synthetic RNA to create a dramatic improvement in the speed and cost of DNA editing. This technique is often also called "CRISPR" in the press. The use of CRISPR/Cas9-gRNA complex for genome editing was the American Association for the Advancement of Science's choice for breakthrough of the year in 2015.

CRISPR has been demonstrated to be able to edit genome of human zygote cells (fertilized eggs) but all such experiments have a protocol to destroy the developing embryo after several days.