Gene Drive: Science Can Now Alter Entire Species
CRISPR-Cas9 for Cutting into DNA to Add or Delete Particular Traits
CRISPR-Cas9 Makes Gene Drive Possible
CRISPR-Cas9 is a customizable tool that lets scientists cut and insert small pieces of DNA at precise areas along a DNA strand. The tool is composed of two parts: the Cas9 protein, which acts like the wrench, and the specific RNA guides, CRISPRs, which act as the set of different socket heads. These guides direct the Cas9 protein to the correct gene on the DNA strand, that controls a particular trait. This lets scientists study our genes in a specific, targeted way and in real-time. (Wikimedia)
Changing the Natural World to Meet Our Needs and Desires
My work as a traveling hospital laboratory technician takes me all over the United States. Each place I go, I try to find out what the locals do for fun, and then I join in. Recently I was in Columbus, Georgia. Over the last few years, since the removal of several dams that were not being used any longer, the Chattahoochee River has become a big deal. White water rafting, kayaking and fishing are the main activities.
I did the rafting and kayaking, so I purchased a fishing pole, tackle and bait and went down the river to catch a striped bass. It was 5:00 a.m. when I arrived and on my second cast, I pulled in a nice striper. Yay me! I fished for several more hours, but kept having my live bait, a fish called a shad, bitten in half....catfish. Wouldn’t it be nice, I thought, if catfish didn’t like shad? Then I would be catching striped bass and not trying not to catch catfish.
Now that gene drive has become a reality, that very thing could happen. That’s right, catfish could be genetically engineered not to like shad. I wonder if sharks could be engineered not to like people.
Definition of Gene Drive
In order for us to understand gene drive, it is helpful to have grasp of the two words individually, as they are used in science. Then we can put them back together and all of this will make more sense. Pay attention to the italicized and underlined words in the definitions.
Gene- A unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring (wikipedia)
Drive-This has been defined as Inheritance biasing. The drive is a chosen character trait which is inserted into individuals of a targeted species via genetic modification.
Gene Drive- The practice of "stimulating biased inheritance of particular genes to alter entire populations of a species.” (Wikipedia). After the character trait has been inserted into the genetic makeup of the target species in the laboratory, e.g. a mosquito, the laboratory line is released into the wild. The character trait is then passed on to the rest of the species through natural mating.
CRISPR/cas9- A genome editing tool found in the immune system of certain bacteria. This substance is inserted into a cell of one of the target species where it cuts into the DNA so that character traits can be eliminated or added. Without CRISPR/cas9, gene drive would still be science fiction.
Designer Cats, Possibly?
An Illustration of Gene Drive
Suppose you want your cat to be pink. No, not the female pop/rock singer, I mean the color pink. You could buy a can of spray paint and hope you don’t get arrested for animal cruelty. But what if you want your cat’s next litter of kittens to all be pink as well? The fact that you spray paint the mother does not mean the kittens will be born the same color.
This is where gene drive applies. Using CRISPR/cas9, the DNA of your cat could be altered so she would produce only pink kittens. But there are more important applications being considered by scientists now that gene drive is no longer science fiction, but reality.
Blue Eyes for Everyone?
Some Interesting Facts About Gene Drive
Under normal, natural circumstances, character traits are passed on from parent to offspring about fifty percent of the time. Using gene drive this could be increased dramatically. Over several generations, every individual of an entire species could be altered to possess the desired trait.
It would take several generations for a particular species to be completely altered with gene drive technology. If this was ever used to alter the human species, it would take centuries because of the length of a human generation. Mosquitos can pass through many generations in a matter of months which means the entire population of a species of mosquitos could be altered in a very short period of time.
Gene drive can only be used in species which sexually reproduce. This discounts viruses and bacteria.
Meet, Anopheles gambiae
Proposed Future Applications of Gene Drive
The following diseases (and more) spread by mosquitoes, could be eliminated by the use of gene drive:
- yellow fever
- West Nile
- sleeping sickness
Invasive species are species that are non-native to a particular ecosystem and whose presence may have environmental, economic or human health consequences. Gene drive could be used to eradicate invasive species.
Pesticide and herbicide resistance in weeds is a growing concern. Gene drive could eliminate this character trait in weeds and insects.
The HIV virus enters a human cell and attaches itself to chromosomes and other genetic material, using them to multiply it’s own genome. Gene drive technology could insert the CRISPR/cas9 genome editing tool into the cell and edit out the HIV genome thereby preventing a recurrence.
I suppose gene drive is another type of genetic modification. We recognize that from the debate about genetically modified food crops, a practice many are opposed to. What should be our reaction to this technology? Should we use it to eliminate diseases, increase crop yield, wipe out invasive species? And what about using it on humans? Scientists claim that applying this technology to achieve "designer babies" is not in their plans. What about gene drive and terrorism? Could this technology be used against us by terrorists?
Science is ever moving forward. That is what science does and will always do. Gene drive is here, like it or not, and having a basic understanding of the technology will help us respond in timely and knowledgable ways.
I hope this extremely elementary article on gene drive is just the beginning of your education regarding this fascinating breakthrough in genetics.