Clustered regularly interspaced short palindromic repeats (CRISPR)
Clustered regularly interspaced short palindromic repeats (CRISPR) is a revolutionary genetic editing tool derived from a natural defense mechanism found in bacteria. Initially discovered in the 1980s, CRISPR consists of a series of repeating DNA sequences that help bacteria combat viral infections. Researchers recognized that by harnessing this mechanism, they could create a more efficient and precise method for editing genes across various organisms, including plants, animals, and even humans. The CRISPR system typically involves the Cas9 protein, which acts like molecular scissors to cut DNA, and a guide RNA that directs Cas9 to the specific genetic sequence to be altered.
While the potential applications of CRISPR are vast—ranging from disease treatment to agricultural improvements—ethical considerations surround its use, especially regarding human gene editing. As the technology becomes more accessible, concerns have been raised about the implications of "do-it-yourself" kits and the long-term impacts of genetic changes, which can be passed down to future generations. Regulatory bodies in the UK and the US have recently begun approving CRISPR-based treatments, such as for sickle cell disease, highlighting both the promise and the challenges posed by this groundbreaking technology. The discussion around CRISPR emphasizes the need for careful consideration of its ethical dimensions, particularly in relation to potential unintended consequences, such as those associated with gene drive techniques that could alter entire populations.
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Clustered regularly interspaced short palindromic repeats (CRISPR)
Clustered regularly interspaced short palindromic repeat (CRISPR) is a cluster of repeating DNA that scientists found in bacteria. CRISPR is most famous for being the basis of a gene editing tool. The CRISPR DNA pattern allows scientists to more easily delete and replace genetic information. The implications of CRISPR continued to be researched, but most scientists believe CRISPR is one of the most important advances in the field of genetics. Although CRISPR has already made important changes in science, many remained concerned about the ethics of using CRISPR. Changing an organism's genetics will have important implications, and ethicists, scientists, governments, and citizens have discussed the advantages and disadvantages of using CRISPR and, specifically, using CRISPR in humans.
Background
CRISPR has been an important development in the field of genetics. Genetics is the study of genes and DNA, which is the chemical code that tells how living things grow and function. All living things have DNA. Most members of a particular species have almost identical genes. However, some genes are different. These differences account for the variations among individual members of a species. For example, in humans, genes can affect how tall a person grows or what color a person's eyes are. Genes also can affect a person's health by causing a particular illness. Scientists have realized since the early twentieth century that genes and DNA act like blueprints for life. If the blueprints are changed, the organism will change, too. Scientists began attempting to edit genes at the end of the twentieth century. Even until the early twenty-first century, the gene-editing techniques available to scientists were unreliable and difficult to use. CRISPR dramatically changed genetics because it is a much easier-to-use and more reliable gene editing tool than any other scientists have found.
CRISPR was first discovered in Japan in the 1980s. Scientists were studying the DNA of Escherichia coli (E. coli) bacteria when they noticed a repeating pattern. Scientists were interested in the repeating DNA pattern because they realized that these repeating patterns, which they found in many types of bacteria, most likely played an important role in the organisms. Yet, the Japanese scientists did not immediately recognize the function of the pattern. As scientists continued to study the pattern, they realized that virus DNA appeared between the repeating patterns inside the bacteria.
Overview
After more research, some scientists posited that CRISPR was acting as a method of protection for the bacteria. Viruses are a huge threat to bacteria; therefore, bacteria have had to develop advanced methods of fighting viruses. CRISPR is one method bacteria evolved to protect themselves. The bacteria have specialized proteins that try to attack and kill viruses. These proteins can use copies of the virus DNA to better "recognize" viruses. Once the proteins recognize a virus from the virus's DNA, they cut the virus's DNA, which kills it.
CRISPR has been important for bacteria, as they have developed a way to keep themselves safe from viruses. Scientists who learned how CRISPR worked realized that this specialized system was unique and important. A few scientists thought that CRISPR might have even more far-reaching effects. CRISPR made it simpler to find particular strands of DNA and cut them. Scientists believed that they could harness CRISPR and use it as a gene editing tool.
Since the early 2000s, scientists have been using CRISPR to edit genes. To use CRISPR to edit genes, scientists have created a system made up of a protein called Cas9 and a guide RNA, which is a string of genetic code. The Cas9 protein is the part of the system that cuts the DNA. People have often compared the protein to a pair of scissors. The other part of the system, the RNA, guides the protein to cut the correct DNA. When the Cas9 protein searches for the DNA to cut, it uses the new RNA to "recognize" the pattern that scientists want to delete or replace. Once the Cas9 finds the correct genetic sequence, it cuts that DNA. Scientists can then replace the cut DNA with a different piece of DNA just by introducing the new DNA to the cut section. The genetic material "fills in the blank" left behind by CRISPR's cutting. (If no new DNA is introduced, scientists can cut out specific sections of DNA, or the cut DNA can sometimes mend itself.)
Using CRISPR to edit genes has dramatically changed the field of genetics. Although scientists have seen a huge potential for CRISPR to cure diseases and improve crop growth, most scientists and many other experts have had concerns about CRISPR. Since CRISPR can alter DNA, the changes made can be passed down to future generations. Humans have never before had such a simple way to alter human, animal, and plant genes. One of the main ethical concerns about using CRISPR is the idea of using it on humans. Only a few scientists have attempted to use CRISPR on human embryos, and many scientists have called for a moratorium on human testing. Since changes made using CRISPR can be passed down through generations, it is important for scientists to fully understand any changes they make. Scientists and ethicists must also determine when, if ever, it is appropriate to use CRISPR on human genes. Do-it-yourself CRISPR kits have also even been available for purchase, raising concerns that this extremely powerful tool can be used by almost anyone with enough knowledge and monetary means.
In what was considered a major milestone for CRISPR-based gene editing, in late 2023 the UK's Medicines and Healthcare products Regulatory Agency, followed by the Food and Drug Administration in the United States, became the first in the world to approve a treatment for sickle cell disease using the CRISPR tool. While the approvals had come after successful clinical trials, some experts still warned about the unknowns of long-term efficacy as well as accessibility inequity due to the expense of the treatment.
Another ethical challenge concerning CRISPR is the use of something called gene drive. When scientists use gene drive, they not only change the DNA of an organism but also encode CRISPR itself into an organism. When CRISPR is encoded in the DNA, the CRISPR change will most likely spread throughout an entire population and possibly into an entire species. Scientists have worried about the ramifications of gene drive because they cannot be sure that the changes they make to a population or an entire species will not have cascading effects. For example, some scientists have experimented with using gene drive to remove the gene that allows mosquitoes to carry malaria, which is a deadly disease. Some argued that although that change could be beneficial in that it could eradicate malaria, the change could have unpredictable side effects.
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