How Gene Editing Works

By Sumay Mcphail

There are people, perfectly normal people, walking the streets today that have had their DNA edited. In the past five years scientists and biologists have been testing and making breakthroughs in the field of genomics and gene editing. So how does editing genes work? And what are your genes even made of?

DNA, also known as deoxyribonucleic acid, is the instruction manual of your body. DNA does many things such as produce the proteins in your body. Sometimes there can be mutations in DNA that can cause a variety of genetic diseases. Sickle cell and huntingtons are examples of mutations in only one gene or piece of DNA. There are also genetic diseases that are caused or at least influenced by many different genes such as Alzheimer's, heart disease and diabetes.


Genetic sequencing is a new technology that allows you to read your DNA. This is helpful for many reasons. One is that you can quickly identify genetic mutations before they become too harmful. You can also see who is at high risk of developing certain diseases. This is great to help people get treatments or therapies that may reduce symptoms, or to get on preventatives early before they develop diseases. But this doesn’t solve the problem of the people who have genetic diseases already, and how to cure them.


Humans have been genetically modifying plants using a method called selective breeding. However, we have never been able to precisely select a certain strand of DNA you want to edit, and then edit it out, or modify it, until five years ago. CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats, which basically is describing the pattern found in DNA. CRISPR essentially is a way that humans are able to directly change the DNA in plants, animals, and even humans.


In a research project, scientists were trying to understand how bacteria could fight against viruses. And this came to the discovery that CRISPR is actually how this is done. CRISPR, when helping bacteria fight against viruses, detects the DNA of the virus and destroys it. But the breakthrough that allowed us the possibility of editing genes was that CRISPR, this adaptive immune system, could be programmed by humans to edit certain genes.


So how does this work? CRISPR is made up of two things, a protein called CAS9 and RNA. CAS9 is able to cut DNA and edit it, but in order to identify which strands of DNA to cut, it needs RNA to know what DNA to look for and edit. RNA, ribonucleic acid, is similar to DNA, and basically carries out the instructions provided by DNA. By mixing CAS9 and artificial, constructed RNA, CAS9 can target certain DNA based on the RNA strand, and edit it. This combination of RNA and CAS9 is CRISPR.



CRISPR can do many things such as cut out DNA, and switch out as little as one piece of DNA allowing for the cure of diseases like sickle cell which is caused by only one mutation in someone's DNA. CAS9 is a protein that can edit someone's genes but there is also another protein, CAS3, that works similarly, but has some differentiating factors that could lead to more possibilities with CRISPR. CAS9 cuts off DNA, but sometimes CAS9 is used to cut off DNA so new DNA can form. CAS3 makes it so that the cut is permanent and completely eliminates the DNA you want to get rid of. One exciting aspect is that there may be more proteins to be found in this same class of proteins that could lead to even more possibilities with what we can do with CRISPR.


CRISPR can and already has edited the DNA of humans to cure genetic diseases. All the way back in 2015 a baby girl was cured of leukemia using this technique. There are many trials going on right now for cures to treat these genetic diseases. But there is a lot of debate on what we should and shouldn’t do with this technology. In secret, a chinese doctor edited the genes of twin girls to make them immune to HIV before they were born. This received a lot of criticism from the scientific community as they were trying to tread lightly and gather data before trying to edit genes that weren't necessary. The twin girls weren’t at high risk of death because of HIV and this was seen as a rash act by biologists and scientists around the world.


Genomics sequencing has also become substantially cheaper and has fallen from 2.7 million dollars in 1990 to only 300 dollars in 2020. As a result of this many people have gotten their gene sequenced adding up to 40 million human genomes sequenced by 2020 and an expected 52 million by 2025. As gene sequencing gets cheaper and cheaper it is highly probable that genetic sequencing will become a standard part of checkups and gene editing will become the common treatment for genetic diseases. Illumina, Invitae and other companies are making genomic sequencing cheaper than ever before and hopes to make genetic sequencing cheap enough so anyone can get their DNA sequenced. This could save millions of lives by identifying genetic diseases early and in an easily accessible way.


There are also animals that are genetically edited for consumption. A company, AquaBounty, genetically modified salmon to grow 30% faster and be able to survive on roughly 70% of food compared to regular salmon. This can make major impacts, not only on the market for salmon, but also other animals if production for raising animals is faster and cheaper. As the possibilities of CRISPR expand with new breakthroughs and cures, the ideas of what we can do with this technology keep growing. For example, some people are thinking of editing the genes of animals to make them more resistant to climate change. However, before making changes and releasing them out into nature, we need to consider all the consequences and backlashes that could come from these unnatural changes.


There are many experiments being done on other animals to see the possibilities of CRISPR. There was a glowing cat created by taking the DNA from a glowing jellyfish that created glowing proteins, and put it in a cat. There were also mice and dogs that had their muscle mass increased by 200% - 300% just by editing their genes. As we tread deeper into the possibilities and breakthroughs of CRISPR the real question will become what should and shouldn’t we do? And how can we prevent these changes from becoming hazardous?


Genomic sequencing and gene editing provide a window for many good and bad things to happen. People are being cured from life threatening genetic diseases, but one hasty change released out into nature could potentially cause catastrophic damage to our ecosystem. Where do you stand on this everlasting ethical debate on gene editing? Where’s the line between curing people of genetic diseases to editing the genes of unborn children to make them taller? As these dreams become reality, there is much debate around what will become of this technology.


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