Page 17 - Breeding Edge ebook

Source: DuPont Pioneer. For more on CRISPR-Cas, go to https://crisprcas.pioneer.com)

Proteins, or genes, “in the nucleus of any organism provide all the information it uses to operate and
grow,” explained Jennifer Doudna, professor of molecular and cell biology and chemistry at the
University of California, Berkeley, speaking at a conference on CRISPR in California. “You can think
of it like a text that includes instructions and a construction manual.” Gene editing is “a way of
modifying that document … you can cut and paste” the proteins in the nucleus, she said.

Speaking more technically, both CRISPR and TALEN use enzymes that sever the double-strands of an
organism’s genes at targeted locations, making what is called double-strand breaks (DSBs), and often

making several such cuts.

Then, DSBs are repaired by sending replacement genes to the
severed site, using a sequence of genes as a template that includes
the modification the breeder wants to make. Also, in both systems,
other insertions or deletions of proteins are made at the break site
as the broken ends are rejoined.

In the CRISPR process (also called CRISPR-Cas9), the activating Jennifer Doudna, University of
California - Berkley
enzyme is a Cas9 nuclease, and the template of replacement genes
is guided to its target in a single strand of ribonucleic acid (RNA).

Similarly, TALEN uses a nuclease to make double breaks, but
employs a pair of double-stranded DNA binding proteins rather

than a single RNA strand. Luckily for plant and animal breeders,
and perhaps all of agriculture, “there are lots of applications of
gene editing,” Slutsky points out. They are used to insert genes or

knock them out, tag their location on a chromosome, correct

www.Agri-Pulse.com 15