CRISPR and Gene Editing

Introduction

I have always been fascinated with gene editing technology because I never actually quite understood it. But recently, I have been taking more interest in biology and microbiology, so I thought of finding more information on this and getting to understand what this gene editing actually is used for and how it works, and then maybe share it with everyone through my blog. So, here is how it works.

Imagine a world where we can edit genes as easily as we edit a document on our computers. To understand how massive this truly is, we need to understand what a gene is. A gene is what makes us who we are. It is the thing that creates our personality, our body shape, our eye color. Everything is controlled by genes. It is the basic unit of heredity passed from parent to child. They are made up of sequences of DNA and are arranged, one after another, at specific locations on chromosomes in the nucleus of cells. Being able to change something like this just sounds like something straight out of a science fiction movie, right? Well, thanks to the revolutionary technology called CRISPR, this is becoming our reality. Over the past decade, CRISPR-Cas9 has emerged as the most promising technique in biotechnology, offering unprecedented control over the genetic information of living organisms. This means we are now able to control how your body or personality is going to be more than ever. This has a huge impact on our lives and how we perceive our human body.

What is CRISPR?

CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. This term refers to short, repeated sequences of DNA found within the genomes of prokaryotes like bacteria and archaea. First discovered by Atsuo Nakata and his team at Osaka University in 1987, these sequences are the same when read forwards or backwards, much like the word “racecar.”

CRISPR’s true significance was uncovered in the mid-2000s when scientists realized that it plays a crucial role in the adaptive immunity of bacteria. Just like humans can develop immunity to viruses through exposure, bacteria use CRISPR to remember past infections. When a virus attacks, bacteria incorporate a snippet of the viral DNA into their own genome, creating a “memory” of the virus. This allows them to recognize and combat the virus more effectively in future attacks.

How Does CRISPR-Cas9 Work?

CRISPR-Cas9 works like a pair of molecular scissors, cutting DNA at specific locations. Here’s a step-by-step breakdown of how it works:

1. Spacer Acquisition: When a virus infects a bacterium, a piece of the viral DNA (called a spacer) is inserted into the bacterium’s CRISPR array, which consists of repeated palindromic sequences.
2. CRISPR RNA (crRNA) Formation: The CRISPR array is transcribed into a long RNA molecule, which is then processed into shorter crRNA molecules, each containing a spacer sequence.
3. Cas9 Involvement: Cas9, a nuclease protein, binds to the crRNA. This complex is guided to the matching viral DNA by the crRNA.
4. DNA Cleavage: If the crRNA matches a sequence in the invading viral DNA, Cas9 cuts the DNA, rendering the virus harmless.

This natural defense mechanism in bacteria has been adapted by scientists for use in other organisms, including humans.

The Breakthrough in 2012

In 2012, Jennifer Doudna and Emmanuelle Charpentier proposed using the CRISPR-Cas9 system as a programmable toolkit for genome editing in humans and other animals. This groundbreaking work earned them the Nobel Prize in Chemistry in 2020.

The key innovation was the creation of a single guide RNA (sgRNA) by combining crRNA and tracrRNA. This simplified the system, allowing precise targeting and cutting of DNA at desired locations. Once the DNA is cut, the cell’s natural repair mechanisms take over, either by non-homologous end joining (NHEJ), which can introduce small insertions or deletions, or by homology-directed repair (HDR), which uses a template to guide accurate repair.

Applications of CRISPR

CRISPR’s potential applications are vast and varied:

1. Genetic Research: CRISPR can be used to identify the functions of specific genes by knocking them out and observing the effects.
2. Medicine:

• Cancer Immunotherapy: T cells can be modified to better recognize and kill cancer cells.
• HIV/AIDS: CRISPR can target and eliminate latent HIV reservoirs in the body, offering hope for a cure.
• SARS-CoV-2 Detection: CRISPR-based tests can quickly and accurately detect the presence of the virus causing COVID-19.

1. Agriculture: CRISPR can be used to create crops that are resistant to diseases, have improved traits, and yield more produce.
2. Gene Therapy: CRISPR holds the promise of curing genetic diseases by correcting mutations at their source. However, ethical concerns and potential risks need careful consideration.

CRISPR-Cas9 is ushering in a new era in molecular biology with its precise, versatile, and powerful gene-editing capabilities. From advancing medical research and treatment to revolutionizing agriculture, the possibilities are endless. As we continue to explore and refine this technology, the future of genetic science looks incredibly promising. Whether it’s curing diseases or creating better crops, CRISPR is set to change the world in ways we can only begin to imagine.