Page 16 - Breeding Edge ebook

disciplines.” With the new techniques, they are “doing the same things that breeders have always
done, but very precisely,” she said.

The precision Slutsky describes did not suddenly burst forth full-blown but is what researchers have
built in recent decades. Some milestones include:

• Development of a technique called polymerase chain reaction in
the 1980s. It allows researchers to duplicate a fragment of DNA
proteins thousands or millions of times, providing a quick and
cheap supply of specimens for their research.

• Another key gene editing tool, zinc-finger nucleases (ZFN),
emerged more than a decade ago. ZFN are enzymes that target
sequences of genes on chromosomes where genetic amendments
are sought. This is similar to the newer gene editing processes but
is considered more laborious and often less successful.

• What’s more, in the past two decades or so, scientists have laid the Bernice Slutsky, American
table for gene editing by locating and cataloging – called Seed Trade Association
sequencing – the entire genomes of a multitude of plants and

animals. That makes virtually every gene potentially available for breeders to find and amend or

delete. Full sequencing has been done for cattle, chickens and pigs. In addition, the sequenced

genomes of almost 200 different plant species have been published, according to Todd Michael,
who’s been tracking plant sequencing as director of informatics for the J. Craig Venter Institute in

California.

With such advances in place, two processes developed in recent years are accelerating breeders’ ability
to genetically alter crops and animals and apply the brakes to harmful organisms. Both can precisely
improve a plant or animal without incorporating DNA from another species. One process is a mouthful
called Clustered Regularly Interspaced Short Palindromic Repeats, or CRISPR, and the other is a
similarly large swallow called Transcription Activator-Like Effector Nucleases (TALEN).

So, how do these genome-amending systems work?

Some have described CRISPR-Cas to be like editing text in a word processing application. With a
specific goal in mind, the CRISPR-Cas system performs a specific search within DNA – an organism’s
complete set of instructions – to delete, edit or replace target genetic sequences.

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