How CRISPR lets you edit DNA - Andrea M. Henle

Summary

CRISPR, a natural bacterial immune system, has revolutionized gene editing with its precision and affordability. It works by using guide RNA to direct the Cas9 protein to target genes, enabling scientists to edit DNA with ease. Applications range from curing genetic diseases to enhancing crops and even reprogramming cancer cells. However, the technology raises ethical concerns due to its potential for unintended changes and long-term impacts.

Takeaways

• 🧬 Genes define every living organism and their DNA acts as an instruction manual for cells, with traits determined by sequences of four bases.
• 🛠️ Gene editing tools, such as CRISPR, allow scientists to alter an organism's fundamental features rapidly and precisely.
• 🍎 Scientists can use gene editing to create beneficial modifications like drought-resistant crops and apples that don't brown.
• 🏥 Potential applications of gene editing include preventing infectious diseases and developing cures for genetic disorders.
• 🔍 CRISPR is a natural process that functions as a bacterial immune system against viruses, using CRISPR sequences and Cas proteins.
• 🔑 The CRISPR-Cas system captures viral DNA and uses it to create RNA that guides the immune response against future invasions.
• 🧬 In 2012, scientists discovered how to repurpose CRISPR for gene editing, targeting any DNA sequence in almost any organism.
• 🧬 The CRISPR-Cas9 complex can be directed to specific genes using guide RNA, allowing for precise DNA cutting and editing.
• 🛠️ DNA repair mechanisms, such as nonhomologous end joining and homology directed repair, are leveraged by CRISPR for gene editing.
• 💡 CRISPR has the potential to treat genetic diseases like cystic fibrosis or sickle cell anemia by correcting DNA errors.
• 🌱 Beyond human applications, CRISPR can be used to enhance plants, modify mosquitoes to prevent disease transmission, and reprogram cancer cells.
• 🔬 CRISPR is a powerful tool for genomic research, enabling the study of gene function through targeted gene activation or deactivation.
• ⚠️ Despite its potential, CRISPR editing is not without risks, as it may introduce unintended changes and raises ethical concerns.

Q & A

What is the primary function of DNA in living organisms?

DNA acts like an instruction manual for cells, with sequences of four building blocks called bases that tell the cell how to behave and form the basis for every trait.

What recent advancements have allowed scientists to change an organism’s fundamental features quickly?

Recent advancements in gene editing tools, such as CRISPR, have allowed scientists to change an organism’s fundamental features in record time.

What are some practical applications of gene editing using CRISPR?

Gene editing using CRISPR can engineer drought-resistant crops, create apples that don’t brown, prevent the spread of infectious outbreaks, and develop cures for genetic diseases.

Where does the CRISPR technology originally come from?

CRISPR is a natural process that originally functions as a bacterial immune system, defending single-celled bacteria and archaea against invading viruses.

What are the two main components of naturally occurring CRISPR?

The two main components of naturally occurring CRISPR are short snippets of repetitive DNA sequences called CRISPRs (clustered regularly interspaced short palindromic repeats) and Cas (CRISPR-associated) proteins.

How do Cas proteins contribute to the CRISPR immune response in bacteria?

Cas proteins cut out a segment of the viral DNA and stitch it into the bacterium’s CRISPR region, capturing a chemical snapshot of the infection. If the virus invades again, Cas9 swiftly destroys the viral DNA.

How did scientists in 2012 advance the use of CRISPR technology?

In 2012, scientists figured out how to hijack CRISPR to target any DNA in almost any organism, transforming it into a precise gene-editing tool.

What is the key to CRISPR's power in gene editing?

The key to CRISPR’s power is the ability to design a guide RNA to match the gene they want to edit, attach it to Cas9, and use the protein’s molecular scissors to snip the DNA, allowing for precise editing.

What are the two types of DNA repair processes mentioned in the script, and how do they differ?

The two types of DNA repair processes are nonhomologous end joining, which is prone to mistakes and can lead to unusable genes, and homology directed repair, which uses a template DNA to guide the rebuilding process, allowing for precise corrections or insertions.

What potential medical advancements could CRISPR bring?

CRISPR could potentially create new treatments for diseases linked to specific genetic errors, like cystic fibrosis or sickle cell anemia, and even reprogram drug-resistant cancer cells.

What are some of the ethical considerations surrounding the use of CRISPR technology?

CRISPR raises ethical questions because it doesn’t always make just the intended changes, and it’s difficult to predict the long-term implications of a CRISPR edit, making it important to decide the best course forward.

Outlines

00:00

🧬 Understanding Genes and Gene Editing

From the smallest single-celled organisms to the largest creatures on Earth, every living thing is defined by its genes. DNA acts like an instruction manual for our cells, composed of four bases arranged in precise sequences that determine our traits. Recent advancements in gene editing tools allow scientists to change an organism’s fundamental features quickly. They can engineer drought-resistant crops, create apples that don’t brown, prevent infectious outbreaks, and develop cures for genetic diseases. CRISPR is the fastest, easiest, and cheapest gene editing tool driving this scientific revolution.

05:02

🔬 Origins and Function of CRISPR

CRISPR, a groundbreaking gene editing tool, originates from a natural process that serves as a bacterial immune system. Initially discovered defending bacteria and archaea against viruses, CRISPR involves two main components: repetitive DNA sequences known as CRISPRs and Cas proteins that act like molecular scissors to cut DNA. When a virus invades, Cas proteins cut out a segment of viral DNA and stitch it into the bacterium’s CRISPR region, creating a chemical snapshot of the infection. This allows the bacterium to recognize and destroy the virus if it invades again.

🧪 CRISPR as a Gene-Editing Tool

In 2012, scientists adapted CRISPR to target not just viral DNA but any DNA in almost any organism, transforming it into a precise gene-editing tool. In the lab, scientists design a guide RNA to match the gene they want to edit and attach it to Cas9. The guide RNA directs Cas9 to the target gene, and the protein cuts the DNA. By injecting Cas9 bound to a custom guide RNA, scientists can edit practically any gene in the genome. The cell attempts to repair the cut DNA, but the process is prone to errors, often resulting in an unusable gene.

🧬 Advanced DNA Repair with CRISPR

CRISPR’s gene-editing potential is further enhanced by using a template DNA sequence during the repair process. Cellular proteins use this template to guide the rebuilding of the DNA, allowing for precise repair of defective genes or the insertion of new ones. This capability means CRISPR could create new treatments for genetic diseases like cystic fibrosis or sickle cell anemia. Beyond humans, CRISPR could be used to create larger fruit, malaria-resistant mosquitoes, or reprogram drug-resistant cancer cells. It also serves as a powerful tool for studying the genome.

⚖️ Ethical Considerations and Future of CRISPR

Despite its potential, CRISPR isn’t perfect and can sometimes make unintended changes. Predicting the long-term implications of CRISPR edits is challenging, raising significant ethical questions. As CRISPR technology advances beyond single-celled organisms and into various applications worldwide, it’s crucial to deliberate on the best course forward. Ethical considerations will play a significant role in shaping the future of CRISPR in labs, farms, hospitals, and organisms globally.

Keywords

💡Genes

Genes are segments of DNA that contain the instructions for the development and function of living organisms. In the context of the video, genes are fundamental to defining every living thing, acting as the blueprint for cells and determining traits. The script mentions that gene editing tools can alter an organism's features, highlighting the significance of genes in shaping life forms.

💡DNA

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms. The video script describes DNA as an 'instruction manual' for cells, composed of sequences of four bases that dictate cellular behavior and form the basis for traits.

💡Base Pairs

Base pairs are the fundamental building blocks of DNA, consisting of four types: adenine (A), thymine (T), cytosine (C), and guanine (G). The script explains that these bases are strung together in precise sequences within DNA, which is crucial for the genetic information they carry and how cells interpret these instructions.

💡Gene Editing

Gene editing refers to the process of adding, deleting, or altering the genetic material within an organism's genome. The video discusses advancements in gene editing tools that allow scientists to change an organism's fundamental features, such as creating drought-resistant crops or preventing the spread of diseases, emphasizing the power and potential of this technology.

💡CRISPR

CRISPR, which stands for 'Clustered Regularly Interspaced Short Palindromic Repeats,' is a revolutionary gene-editing tool. The script describes CRISPR as a natural process originally used by bacteria as an immune system against viruses, but has been harnessed by scientists for precise gene editing in various organisms.

💡Cas Proteins

Cas proteins, or 'CRISPR-associated' proteins, are enzymes that play a key role in the CRISPR immune system of bacteria. As explained in the script, these proteins act like molecular scissors, chopping up DNA. In the context of CRISPR technology, Cas proteins, particularly Cas9, are used to cut and modify DNA at specific locations.

💡RNA

RNA, or ribonucleic acid, is a molecule involved in various biological roles, including coding, decoding, regulation, and expression of genes. The video script mentions that in CRISPR, RNA binds to the Cas9 protein to form a complex that seeks out and binds to specific DNA sequences, illustrating RNA's crucial role in the gene-editing process.

💡Guide RNA

Guide RNA is a custom-designed segment of RNA used in CRISPR technology to direct the Cas9 enzyme to the precise location in the genome where editing is desired. The script explains that scientists design guide RNA to match the gene they wish to edit, showcasing its importance in the specificity of gene editing.

💡Homology Directed Repair (HDR)

Homology Directed Repair is a DNA repair process that uses a template DNA sequence to guide the repair of a cut or damaged DNA strand. The video describes how, with CRISPR, scientists can add a template DNA to induce HDR, allowing for the repair of defective genes or the insertion of new genetic material.

💡Nonhomologous End Joining (NHEJ)

Nonhomologous End Joining is a DNA repair mechanism that rejoins broken DNA ends without the use of a template. The script points out that NHEJ is error-prone and can lead to mutations, such as the addition or deletion of DNA bases, which often results in the gene being unusable.

💡Ethical Questions

Ethical questions arise when considering the implications and potential misuse of powerful technologies like CRISPR. The video script raises these concerns, noting that while CRISPR can make unintended changes to the genome and has long-term unpredictability, it also poses significant ethical dilemmas regarding its application.

Highlights

Genes define every living organism, from single-celled bacteria to the largest creatures on Earth.

DNA acts as an instruction manual for cells, with four bases forming the sequences that determine traits.

Gene editing tools allow scientists to change an organism’s features quickly, enabling the engineering of crops and potential cures for genetic diseases.

CRISPR is a revolutionary gene-editing tool that is fast, easy, and inexpensive.

CRISPR is a natural bacterial immune system that uses two main components: CRISPR sequences and Cas proteins.

Cas proteins cut viral DNA and incorporate it into the bacterium’s CRISPR region, creating a chemical snapshot of the infection.

Scientists adapted CRISPR in 2012 to target any DNA, making it a precise gene-editing tool.

In the lab, scientists use guide RNA to direct Cas9 to the target gene, where it makes precise cuts.

CRISPR can edit practically any gene in the genome by using custom guide RNA bound to Cas9.

Nonhomologous end joining is a DNA repair process prone to errors, often resulting in unusable genes.

Homology directed repair uses template DNA to guide the repair, enabling the correction of defective genes or insertion of new ones.

CRISPR's ability to fix DNA errors offers potential treatments for genetic diseases like cystic fibrosis and sickle cell anemia.

The applications of CRISPR extend beyond humans, potentially creating improved crops, disease-resistant mosquitoes, and reprogrammed cancer cells.

CRISPR is a powerful tool for studying the genome, allowing scientists to observe the effects of gene modifications.

Despite its potential, CRISPR is not yet perfect and raises ethical questions due to its unpredictable long-term implications.

Transcripts

From the smallest single-celled organism

to the largest creatures on earth,

every living thing is defined by its genes.

The DNA contained in our genes acts like an instruction manual for our cells.

Four building blocks called bases are strung together in precise sequences,

which tell the cell how to behave

and form the basis for our every trait.

But with recent advancements in gene editing tools,

scientists can change an organism’s fundamental features in record time.

They can engineer drought-resistant crops

and create apples that don’t brown.

They might even prevent the spread of infectious outbreaks

and develop cures for genetic diseases.

CRISPR is the fastest, easiest, and cheapest of the gene editing tools

responsible for this new wave of science.

But where did this medical marvel come from?

How does it work?

And what can it do?

Surprisingly, CRISPR is actually a natural process

that’s long functioned as a bacterial immune system.

Originally found defending single-celled bacteria and archaea

against invading viruses,

naturally occurring CRISPR uses two main components.

The first are short snippets of repetitive DNA sequences

called “clustered regularly interspaced short palindromic repeats,”

or simply, CRISPRs.

The second are Cas,

or “CRISPR-associated” proteins

which chop up DNA like molecular scissors.

When a virus invades a bacterium,

Cas proteins cut out a segment of the viral DNA

to stitch into the bacterium’s CRISPR region,

capturing a chemical snapshot of the infection.

Those viral codes are then copied into short pieces of RNA.

This molecule plays many roles in our cells,

but in the case of CRISPR,

RNA binds to a special protein called Cas9.

The resulting complexes act like scouts,

latching onto free-floating genetic material

and searching for a match to the virus.

If the virus invades again, the scout complex recognizes it immediately,

and Cas9 swiftly destroys the viral DNA.

Lots of bacteria have this type of defense mechanism.

But in 2012, scientists figured out how to hijack CRISPR

to target not just viral DNA,

but any DNA in almost any organism.

With the right tools,

this viral immune system becomes a precise gene-editing tool,

which can alter DNA and change specific genes

almost as easily as fixing a typo.

Here’s how it works in the lab:

scientists design a “guide” RNA to match the gene they want to edit,

and attach it to Cas9.

Like the viral RNA in the CRISPR immune system,

the guide RNA directs Cas9 to the target gene,

and the protein’s molecular scissors snip the DNA.

This is the key to CRISPR’s power:

just by injecting Cas9 bound to a short piece of custom guide RNA

scientists can edit practically any gene in the genome.

Once the DNA is cut,

the cell will try to repair it.

Typically, proteins called nucleases

trim the broken ends and join them back together.

But this type of repair process,

called nonhomologous end joining,

is prone to mistakes

and can lead to extra or missing bases.

The resulting gene is often unusable and turned off.

However, if scientists add a separate sequence of template DNA

to their CRISPR cocktail,

cellular proteins can perform a different DNA repair process,

called homology directed repair.

This template DNA is used as a blueprint to guide the rebuilding process,

repairing a defective gene

or even inserting a completely new one.

The ability to fix DNA errors

means that CRISPR could potentially create new treatments for diseases

linked to specific genetic errors, like cystic fibrosis or sickle cell anemia.

And since it’s not limited to humans,

the applications are almost endless.

CRISPR could create plants that yield larger fruit,

mosquitoes that can’t transmit malaria,

or even reprogram drug-resistant cancer cells.

It’s also a powerful tool for studying the genome,

allowing scientists to watch what happens when genes are turned off

or changed within an organism.

CRISPR isn’t perfect yet.

It doesn’t always make just the intended changes,

and since it’s difficult to predict the long-term implications of a CRISPR edit,

this technology raises big ethical questions.

It’s up to us to decide the best course forward

as CRISPR leaves single-celled organisms behind

and heads into labs, farms, hospitals,

and organisms around the world.