A Tool for Editing the
Genome: Instruction
Manual
Background and Benefits
Scientists have been able to genetically modify living things by cutting and
pasting DNA since the 1970s. In 2013, scientists developed a new technique
for genetic modification that uses repeating patterns in the DNA of many
species. This new technique is called the CRISPR/Cas system (called CRISPR,
pronounced “crisper,” for short). CRISPR works like a search-and-replace
tool in a word processor and allows scientists to edit genomes with much
more precision, efficiency, and flexibility than they had with prior
techniques. It is also faster, lower cost, and easier to use.
Using this technique, scientists can add, change, or take out genes that
make up the DNA of living things. For example, a segment of DNA linked to
an inherited disease could be removed and replaced with a segment that is
not linked to the disease. This could improve the health of animals and
plants, with potential applications in the food supply. Changes made with
this technique may be permanent and can be passed down to future
generations.
The CRISPR technique is only useful where the connection between genes
and the desired or undesired characteristic is well understood. For
example, scientists have identified the gene that may carry a mutation that
leads to a person having the deadly disease sickle cell anemia. It should be
relatively straightforward to use CRISPR to remove the mutated gene and
replace it with an unmutated one. On the other hand, a mosquito’s ability
to find humans has not been mapped to specific gene(s) and likely involves
a combination of genes. Using CRISPR to remove the mutated sickle cell
gene and replace it with an unmutated one should be much simpler than
the mosquito example.
Safety
There are many things to consider when using this tool. It is still a very new
technology with many unexplored risks. Some people fear that the tool is
so effective and easy to use that people may use it before its safety can be
assessed. Others worry about whether the tool should be used in certain
circumstances, or at all. Some policy makers recognize that release and
application of this technology fall outside the scope of many current
regulations addressing genetic modification.
Many of the useful aspects of the CRISPR technique also cause some
concern: faster, lower cost, more accessible techniques may mean more
people editing genomes, including those with less scientific or ethics
training. When processes like gene editing happen outside of wellregulated environments, there are fewer traditional safeguards in place to
ensure compliance with ethical norms.
The technology occasionally cuts DNA in unintended places when the target
gene is too similar to other sequences in the genome.
Unlike other techniques, CRISPR leaves none of the specific identifying
markers that other forms of genetic modification do. This makes it more
difficult to monitor and regulate its use.