Blogs: Technology

By: Nethrakshaya Jakkula

Think of DNA as a giant instruction manual containing all the information needed to build and operate the human body. This manual is written in a code made up of four chemical bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). These bases pair up in specific ways (A with T, and C with G) to form the segments of the DNA ladder. The order of these bases creates genes, which are like specific chapters in the instruction manual that tell cells how to make proteins or the workhorses of the body. Now, imagine there's a typo in this instruction manual, even as small as a single incorrect letter in a gene. This tiny error can sometimes lead to big problems, causing genetic diseases like cystic fibrosis or Huntington's disease. To combat such genetic mutation, scientists are now working on the future of gene-editing, also known as CRISPR. 

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CRISPR, also known as clusters of regularly interspaced short palindromic repeats, is the most advanced gene editing tool in the scientific community till date. For years, it was already being used by bacteria as a defense against viruses. Bacteria are constantly under attack from viruses, and over millions of years, they have developed an effective defense mechanism. They have special sections of DNA, or CRISPR regions, that contain parts of genetic code from past viruses or invaders. These snippets act like a "memory bank" of viral threats. Associated with these CRISPR regions are special proteins called Cas proteins (CRISPR-associated proteins). One of the most famous and widely used Cas proteins is called Cas9, which acts as a pair of molecular scissors that can cut DNA. To target a specific gene in an organism (like a human cell), scientists create a small piece of RNA called a guide RNA. This guide RNA is designed to have a sequence that perfectly matches the specific DNA sequence they hope to edit. The guide RNA then binds to the Cas9 protein. This combination of the guide RNA and the Cas9 protein acts like a guided missile, allowing the guide RNA to lead the Cas9 "scissors" to the exact location in the DNA where the target gene is located. Once it arrives, Cas9 makes a precise double-strand cut in the DNA, so now the cell has its natural DNA repair mechanisms. 

When the DNA is cut, the cell tries to fix it, which scientists can take advantage of in two main ways: Non-homologous end joining (NHEJ) or homology-directed repair (HDR). In non-homologous end joining, the cells stick the broken ends of the DNA back together, which is a process that is often error-prone and can lead to small insertions or deletions of DNA bases at the cut site. This can effectively "knock out" or disable a gene, meaning it is no longer active in the person’s body. In contrast, the process of homology-directed repair is a more precise repair pathway. If scientists give the cell a DNA template, which is a mostly correct version of the target gene, in addition to the CRISPR and Cas9 system, the cell can use this reference point to repair the cut DNA with more accuracy. This allows for very precise gene editing, where scientists can correct a faulty gene or even insert a new piece of DNA. 

The potential applications of CRISPR technology are vast and incredibly exciting. This technology could revolutionize the treatment of genetic diseases, help develop cancer therapies, created plants which disease resistant, develop new tools for disease detection, nad expand understanding of biology as a whole. For instance, CRISPR holds immense promise for correcting the underlying genetic causes of diseases like cystic fibrosis, sickle cell anemia, and Huntington's disease. Furthermore, scientists are already exploring using CRISPR to engineer immune cells to better target and destroy cancer cells which, with enough, development make cancer as easy to fight as a common cold. CRISPR can additionally be used to modify the genes of plants to make them more resistant to pests, diseases, and harsh environmental conditions, potentially leading to higher yields and reduced pesticide use. Moreover, CRISPR can be adapted to create highly sensitive and specific tools for detecting diseases, like cancer, leading to early start for treatment. Finally, CRISPR allows scientists to easily study the function of different genes by "knocking them out" and observing the effects on cells and organisms.