Genetically Engineering Almost Anything

CRISRP-Cas9 allows researchers to edit genomes in a few days.

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Gene drives allow natural sexual reproduction to transmit that gene to every offspring, until the entire population has that modification. Combining these techniques gives genetic engineers unprecedented power.

Cas9-based gene drives are an extraordinarily powerful tool, that will allow one researcher to release an engineered member of a sexually reproducing species to eventually wipe out that species. A field test will be ready within the next few months.

Today, researchers aren’t just dropping in new genes, they’re deftly adding, subtracting, and rewriting them using a series of tools that have become ever more versatile and easier to use. In the last few years, our ability to edit genomes has improved at a shockingly rapid clip. So rapid, in fact, that one of the easiest and most popular tools, known as CRISPR-Cas9, is just two years old. Researchers once spent months, even years, attempting to rewrite an organism’s DNA. Now they spend days.

Soon, though, scientists will begin combining gene editing with gene drives,...

With gene drives—so named because they drive a gene through a population—researchers just have to slip a new gene into a drive system and let nature take care of the rest. Subsequent generations of whatever species we choose to modify—frogs, weeds, mosquitoes—will have more and more individuals with that gene until, eventually, it’s everywhere.

Cas9-based gene drives could be one of the most powerful technologies ever discovered by humankind. “This is one of the most exciting confluences of different theoretical approaches in science I’ve ever seen,” says Arthur Caplan, a bioethicist at New York University. “It merges population genetics, genetic engineering, molecular genetics, into an unbelievably powerful tool.”

We’re not there yet, but we’re extraordinarily close. [emphasis mine]

A gene drive (blue) always ends up in all offspring, even if only one parent has it. That means that, given enough generations, it will eventually spread through the entire population.

Here’s how it generally works. The term “gene drive” is fairly generic, describing a number of different systems, but one example involves genes that code for an endonuclease—an enzyme which acts like a pair of molecular scissors—sitting in the middle of a longer sequence of DNA that the endonculease is programmed to recognize. If one chromosome in a pair contains a gene drive but the other doesn’t, the endonuclease cuts the second chromosome’s DNA where the endonuclease code appears in the first.

The broken strands of DNA trigger the cell’s repair mechanisms. In certain species and circumstances, the cell unwittingly uses the first chromosome as a template to repair the second. The repair machinery, seeing the loose ends that bookend the gene drive sequence, thinks the middle part—the code for the endonuclease—is missing and copies it onto the broken chromosome. Now both chromosomes have the complete gene drive.

Here, a mosquito with a gene drive (blue) mates with a mosquito without one (grey). In the offspring, one chromosome will have the drive. The endonuclease then slices into the drive-free DNA. When the strand gets repaired, the cell's machinery uses the drive chromosome as a template, unwittingly copying the drive into the break.

Gene drives and Cas9 are each powerful on their own, but together they could significantly change biology. CRISRP-Cas9 allows researchers to edit genomes with unprecedented speed, and gene drives allow engineered genes to cheat the system, even if the altered gene weakens the organism. Simply by being coupled to a gene drive, an engineered gene can race throughout a population before it is weeded out.

... the system works best on fast-reproducing species, Esvelt says. Short generation times allow the trait to spread throughout a population more quickly. Mosquitoes are a perfect test case. If everything were to work perfectly, deleterious traits could sweep through populations of malaria-carrying mosquitoes in as few as five years, wiping them off the map.

“If it let’s us do this for mosquitos, what is to stop us from potentially doing it for almost anything that is sexually reproducing?”...

Other noxious species could be candidates, too.

The possibilities seem endless.

As the power of a tool increases, so does its potential for catastrophe, and Cas9-based gene drives could be extraordinarily powerful.

... the time to really get cracking on the legal/ethical infrastructure for this technology is right now.”

I've seen sci-fi shows in which a genetic vector had been tailored to recognize a particular human group, an ethnic group, a family, or an individual, for extermination. Could a genetic modification, in future, be that well tailored? Could someone be engineered to carry a genetic time bomb that spread throughout his or her target group, through reproduction, so that 4 or 5 generations later they all died? It's sounding less fantastic.

Here's a scenario. The Chinese engineer us to self destruct and we engineer them to do so, etc. Then sometime later-  *poof* - within a generation Homo sapiens "mysteriously" dies out.

Tags: CRISPR-Cas9, exterminating species, gene drives, genetic engineering

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