CRSPR Critters


crispr_overview

If you haven’t heard of CRISPR, you will, It’s a tool that, like the transistor in electronics, is utterly revolutionizing biology. Combined with gene drive, it has made alterations to genomes, including human genomes, within the means and skills of a bright high school biology student. Put on your horned-rim glasses and pocket protector; we’re going to get geeky.

Clustered regularly interspaced short palindromic repeats (CRISPR, pronounced “crisper”) are segments of prokaryotic DNA containing short, repetitive base sequences. Small clusters of CAS (CRISPR-associated system) genes are located next to CRISPR sequences. A form of CRSPR-cas has been modified to edit genomes. By delivering the Cas9 nuclease mixed with a synthetic guide RNA (gRNA) into a cell, that cell’s genome can be cut at a desired location, allowing existing genes to be removed and/or new ones added.

WC could get all geeky and nerdy here, and walk you through the genetic mechanism, but it’s not necessary for WC’s point: CRISPR-cas allows biologists to edit any gene, inserting or deleting whatever genetic information they want. RISPR-cas turns genetics into a giant tinker toy system.

One of those possible edits is to transform any gene, one already present in the genome or one that’s been spliced in, and transform it into a “selfish gene,” a “gene drive.” A gene drive is one which always appears in genetic offspring, even if one parent doesn’t carry the gene in the allele. Remember in sexual reproduction, the offspring inherits genes from both both parents. But a selfish gene, a gene drive, replaces the competing allele. Instead of half the offspring carrying the selfish gene, all offspring do.

The combination of CRISPR-cas gene editing and gene drive mean that in a double handful of generation, the genetic edits can dominate the population of a species.

As just one example, geneticists know how to modify an Anopholes mosquito so that it cannot transmit the malaria parasite. If the change is made a gene drive, then all offspring of the genetically modified organism would be similarly disabled. Create a few million of the modified mosquitoes, release them across South America, and in 20 years malaria would be gone. Modify the White-footed Mouse so that it has genetic immunity to wood ticks, breed a couple thousand of little rodents, and in a few years you’d greatly reduce the vector for Lyme Disease.

Like any technology, it can be misused, weaponized as well. You can give yourself the cold sweats thinking of the potential for weapons of terror.

And we haven’t even begun to think about the risks associated with mucking about with the human genome.

Mary Shelley’s Frankenstein looks like a pussycat in comparison.

We can’t out the genie back in the bottle. We can only deal with the consequences. Oh brave new world.

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