Gene Drives: How to Change an Entire Species

Every year, malaria infects and kills millions of people, invasive insects destroy 30% of the world's crops, and rats cause the extinction of hundreds of island birds.

But what if we could modify the genetic blueprints of these mosquitoes so they could no longer get infected by malaria? What if we could make females of a certain species infertile so that species would, gradually, be unable to reproduce? For a long time, scientists have worked to solve these problems, and finally, we have a possible solution: CRISPR-Cas9.

What Are Cells?

For the human species, surviving is our most important job, which we do by adapting and reproducing, among other things. But how are we able to do all of these things? Because of DNA. Just like how every building is made from its blueprints, every living thing is made from its DNA blueprint. Our DNA determines everything from physical features, like the color of your eyes, to behavior. These blueprints, stored inside our genes and alleles, are found in our cells. So what are cells?

Cells are the building blocks of the human body. Your own body is made up of trillions of cells, and they range between 1 to 100 micrometers in diameter. That means that the biggest cell is still 100 times smaller than the thickness of a piece of paper!

Every cell, each of which contains almost all of the important stuff in your body, has a different function. Some do more minor work like repairing your skin after getting a paper cut, and others do more important jobs, like keeping your heart beating every day. Some cells, like sperm and egg cells from your parents, can cause your entire existence in the first place.

Speaking of parents, why are they vital in the animal kingdom and how powerful can their impact be for the next generations?

What are Gene Drives?

With normal inheritance, where the parent’s genes are passed down naturally to the offspring, each allele usually only has a 50% chance of making it into the organisms’ offspring. However, certain plants, fungi, and some other organisms, can get selected genes to have a higher than 50% chance to spread into the next generation. This process is called a gene drive.

The concept of using gene drives to help us has existed ever since the 1960’s, but the idea didn’t really take off until the discovery of CRISPR-Cas9. Scientists found out that by using it, CRISPR could use an organism’s modified gene and other tools to cut out part of the other allele and copy it. (see CRISPR-Cas9 Process) Using this procedure, over time, the entirety of that organisms’ population will be modified.

So What is CRISPR Cas9?

CRISPR-Cas9, or CRISPR for short, is a tool that let’s scientists accurately modify genomes. Using CRISPR, we can modify the genes of a mosquito, then use gene drives to force our modification to the entire mosquito population. Yes, modify an entire population forever. Animals could be modified and promote their own offspring to have the same genetic adjustment, so that the altered offspring can then spread throughout the next generation, and so on.

Let's use malaria as an example. No one likes malaria, right? We could possibly completely stop mosquitoes from spreading it. The current methods we are using against malaria could stop working if the mosquitoes become immune to it. But by using something like CRISPR, we might be able to eliminate that possibility completely.

Some scientists have used CRISPR to modify the mosquitoes DNA so that they were immune to the malaria virus, so they couldn’t transfer it to humans. Furthermore, if we were using gene drives, we don’t even have to affect all of the mosquitoes, we could just target the specific ones that transmit malaria. Using these gene drives we could even render that species’ female mosquitoes infertile, causing egg numbers to drop to 0!

But is it Worth it?

However promising this new technology seems, though, it has some risks and things we should take into consideration. For one, once we start altering these mosquitoes’ genes to get rid of malaria, we don’t know what could happen in the future. Could it lead to newborn animal and/or human diseases? For another thing, if this experiment proves successful, would it be worth the risk of potentially damaging the ecosystem around us? How much should we be able to experiment and alter living beings’ genes? And lastly, once we start using gene editing technologies like CRISPR, could it bring us down a slippery slope, which might be good at first, but be possibly dangerous to pursue?

Scientists have been using test populations to try and see the effects of using a gene drive, and it seems to be working, but there are still many months down the road before we can start releasing these genetically modified mosquitoes.

Once the altered gene is able to spread throughout the entire population, there is no going back. So we have to be absolutely sure before making any drastic changes to our ecosystem or ourselves.

We could technically eradicate the whole of the mosquito population or stop malaria, but is using this new technology really worth it?

SOURCES

1. Creighton, Jolene. “Gene Drives: Assessing the Benefits & Risks.” Future of Life Institute, 6 Dec. 2019, www.futureoflife.org/gene-drives-assessing-the-benefits-risks/.

2. Enzmann, Brittany. “Full Stack Genome Engineering.” Synthego, 4 Dec. 2018, www.synthego.com/blog/gene-drive-crispr#crispr-a-new-tool-for-gene-drive-technology.

3. 29, Associated Press Oct., et al. “Lab Tests Show Risks of Using CRISPR Gene Editing on Embryos.” STAT, Stat News, 29 Oct. 2020, www.statnews.com/2020/10/29/lab-tests-show-risks-of-using-crispr-gene-editing-on-embryos/.

4. Callaway, Ewen. “Controversial CRISPR 'GENE Drives' Tested in Mammals for the First Time.” Nature News, Nature Publishing Group, 6 July 2018, www.nature.com/articles/d41586-018-05665-1.

5. Esvelt, Kevin. “Gene Drives.” Wyss Institute, 28 May 2021, www.wyss.harvard.edu/technology/gene-drives/.

6. N, A. “A New Genome Editing Strategy Offers Potential Way to Control Spread of Insect-Borne Disease and Invasive Species.” Wyss Institute, 4 June 2020, www.wyss.harvard.edu/news/a-new-genome-editing-strategy-offers-potential-way-to-control-spread-of-insect-borne-disease-and-invasive-species/.

7. Kahn, Jennifer. “The Gene Drive Dilemma: We Can Alter Entire Species, but Should We?” The New York Times, The New York Times, 8 Jan. 2020, www.nytimes.com/2020/01/08/magazine/gene-drive-mosquitoes.html.

8. N, A. “Fact Sheet about Malaria.” World Health Organization, World Health Organization, 1 Apr. 2020, www.who.int/news-room/fact-sheets/detail/malaria.

9. Sherely , G H. “Reducing the Rat Threat to Island Birds - Cambridge.” Reducing the Rat Threat to Island Birds, Cambridge, 11 May 2010, www.cambridge.org/core/services/aop-cambridge-core/content/view/E507D79B03D99590CFBB2034938112ED/S0959270900002331a.pdf/reducing_the_rat_threat_to_island_birds.pdf.

10. N, A. “What Is CRISPR-Cas9?” Facts, The Public Engagement Team at the Wellcome Genome Campus, 21 July 2021, www.yourgenome.org/facts/what-is-crispr-cas9.

11. 29, Associated Press Oct., et al. “Lab Tests Show Risks of Using CRISPR Gene Editing on Embryos.” STAT, 29 Oct. 2020, www.statnews.com/2020/10/29/lab-tests-show-risks-of-using-crispr-gene-editing-on-embryos/.

12. N. Wedell N. Wedell orcid.org/0000-0003-1170-8613 Department of Biosciences, N, et al. “Gene Drive: Progress and Prospects.” Proceedings of the Royal Society B, 18 Dec. 2019, Www.royalsocietypublishing.org/doi/10.1098/rspb.2019.2709.

13. Bergman, Mary Todd. “Harvard Researchers Share Views on FUTURE, Ethics of Gene Editing.” Harvard Gazette, Harvard Gazette, 28 Oct. 2019, www.news.harvard.edu/gazette/story/2019/01/perspectives-on-gene-editing/.

14. Ledford, Heidi. “How the Immune System Could Stymie Some CRISPR Gene Therapies.” Nature News, Nature Publishing Group, 8 Jan. 2018, www.nature.com/articles/d41586-018-00335-8.

15. Wasta, Vanessa. “Gene-Editing 'SCISSOR' Tool CRISPR-Cas9 May Also Be a GENETIC 'Dimmer Switch'.” The Hub, 29 Jan. 2021, www.hub.jhu.edu/2021/01/29/crispr-cas9-gene-dimmer/.

16. N, A. “Deoxyribonucleic Acid (DNA) Fact Sheet.” Genome.gov, 24 Aug. 2020, www.genome.gov/about-genomics/fact-sheets/Deoxyribonucleic-Acid-Fact-Sheet

17. N, A. “What Is a GENE?: MedlinePlus Genetics.” MedlinePlus, U.S. National Library of Medicine, 22 Mar. 2021, www.medlineplus.gov/genetics/understanding/basics/gene/.

18. N, A. “Dna, Chromosomes and Gene Expression.” Science Learning Hub, 8 June 2011, www.sciencelearn.org.nz/resources/206-dna-chromosomes-and-gene-expression.

19. N, A. “What Is A Chromosome?: MedlinePlus Genetics.” MedlinePlus, U.S. National Library of Medicine, 19 Jan. 2021, www.medlineplus.gov/genetics/understanding/basics/chromosome/.

20. N, A. “Chromosomes Fact Sheet.” Genome.gov, 15 Aug. 2020, www.genome.gov/about-genomics/fact-sheets/Chromosomes-Fact-Sheet.

21. Higuera , Valencia. “Genes: Function, Makeup, Human Genome Project, and Research.” Medical News Today, MediLexicon International, 14 Mar. 2017, www.medicalnewstoday.com/articles/120574#what_are_genes.

22. Bailey, Regina. “How Do Alleles Determine Traits in Genetics?” ThoughtCo, 21 Aug. 2019, www.thoughtco.com/allele-a-genetics-definition-373460.

23. Mullis , Elise. “Genes Made Easy.” Genes Made Easy | East London Genes & Health, 2021, www.genesandhealth.org/genes-your-health/genes-made-easy.

24. Foundation, CK-12. “12 Foundation.” CK, 2020, www.ck12.org/book/ck-12-biology-advanced-concepts/section/3.5/.

25. Patrão Neves, Maria, and Christiane Druml. “Ethical Implications of Fighting Malaria with Crispr/cas9.” BMJ Global Health, BMJ Publishing Group, 19 Aug. 2017, www.ncbi.nlm.nih.gov/pmc/articles/PMC5656140/.

26. Albert, Helen. “Gene Drives: A CONTROVERSIAL Tool in the Fight Against Malaria.” Labiotech.eu, 2 Nov. 2020, www.labiotech.eu/in-depth/gene-drives-controversy/.

27. Scudellari, Megan. “Self-Destructing Mosquitoes and Sterilized Rodents: The Promise of Gene Drives.” Nature News, Nature Publishing Group, 9 July 2019, www.nature.com/articles/d41586-019-02087-5.

28. Matthews, Dylan. “A Genetically Modified Organism Could End Malaria and Save Millions of Lives - If We Decide to Use It.” Vox, Vox, 31 May 2018, www.vox.com/science-and-health/2018/5/31/17344406/crispr-mosquito-malaria-gene-drive-editing-target-africa-regulation-gmo.

29. N, A. “Cell.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 2021, www.britannica.com/science/cell-biology.