Genome editing

Scientists can change tiny parts of life.

They use tiny tools that act like scissors. These tools cut the tiny code inside a living thing. This helps scientists add, remove, or change parts of that code.

One way they do this is by fixing breaks. When the code is cut, the cell tries to fix it. This can change the code in a new way.

This work can help many things. It can make food better. It can even help sick people.

Scientists use these tools to study how life works. It is a very big discovery.

Scientists can change the tiny code inside living things. This is called genome editing.

In the past, changing this code was hard. It was often random. New tools now let scientists pick a specific spot. These tools are called nucleases. You can think of them as molecular scissors.

First, the nuclease finds a specific part of the DNA. Then, it makes a double-strand break. This is a cut through both sides of the DNA. After the cut, the cell tries to fix it. This repair process can change the code. One way is called NHEJ. This method joins the ends back together. Another way is called HDR. This uses a template to fix the break more accurately.

This work helps many things. Scientists made pigs that can fight a virus. They also made a tomato that helps people relax. In 2020, a trial used CRISPR to help cancer patients. CRISPR is a famous tool used for this work.

Genome editing is a way to change the DNA inside a living thing. This process is also called genome engineering or gene editing. Scientists can insert new DNA, delete old parts, or replace pieces of the code. In the past, genetic engineering was often random. This meant scientists could not pick exactly where new material went. New tools now allow for site-specific editing. This means they can target very precise locations in the genome.

How does this work? It relies on special tools called nucleases. You can think of these as molecular scissors. First, a nuclease finds a specific spot in the DNA. Then, it creates a double-strand break, which is a cut through both sides of the DNA. The cell then tries to repair this break. One way is called non-homologous end joining, or NHEJ. This method joins the DNA ends back together directly. Another way is called homology-directed repair, or HDR. This method is more accurate because it uses a template to fix the break.

People have been working on this for a long time. Genetic engineering has been around since the 1970s. Scientists pioneered genome editing in the 1990s. However, early methods were not very efficient. In 2011, Nature Methods named engineered nucleases as the Method of the Year. These included zinc finger nucleases (ZFNs) and TALENs. Later, the CRISPR-Cas system became very famous. Science magazine named CRISPR the Breakthrough of the Year in 2015.

There are many different types of these molecular scissors. Meganucleases were discovered in the late 1980s. They can recognize very long DNA sequences. Zinc finger nucleases, or ZFNs, use small parts called zinc fingers to find DNA. TALENs are another group of engineered nucleases. In 2018, scientists used these tools to make many different edits. In 2019, a scientist named He Jiankui used CRISPR on human embryos. This event caused much debate around the world.

This science helps us in many everyday ways. Researchers at the Roslin Institute made pigs that resist a specific virus. This helps farmers save billions of dollars. In 2020, a tomato called Sicilian Rouge High GABA was sold in Japan. This tomato makes more of an amino acid that helps people relax. Scientists also used CRISPR to help three cancer patients in a US trial. These tools show how we can change the world of living things.

{ "text": "Genome editing, also known as genome engineering or gene editing, is a precise form of genetic engineering. This technology allows scientists to insert, delete, modify, or replace specific segments of DNA within the genome of a living organism. Unlike older genetic engineering methods, which often inserted new genetic material into a host genome at random locations, genome editing is site-specific. This means scientists can target exact locations to make changes. This precision helps reduce off-target effects, which are unintended changes to other parts of the DNA.

\n\nThe fundamental mechanism of genome editing relies on creating a double-strand break (DSB) in the target DNA. To achieve this, scientists use programmable nucleases, which act like molecular scissors. A nuclease consists of a DNA-binding domain (DBD) that recognizes a specific genomic locus and an effector domain that cuts the DNA. Once the nuclease creates a DSB, the cell naturally attempts to repair the damage through one of two major pathways. The first is non-homologous end joining (NHEJ), where enzymes directly join the broken DNA ends back together. The second is homology-directed repair (HDR), which is a more accurate process. In HDR, the cell uses a homologous sequence as a template to regenerate the missing DNA at the break point.

\n\nScientists have developed several distinct classes of engineered nucleases to perform these cuts. Meganucleases, discovered in the late 1980s, are naturally occurring enzymes that recognize very long DNA sequences, often between 14 and 40 base pairs. While they are highly specific, it is difficult to find a meganuclease that matches a specific desired sequence. To solve this, researchers use mutagenesis or computer models to create custom variants. Another class is Zinc finger nucleases (ZFNs). These use zinc finger motifs, which are small protein structures stabilized by zinc ions, to recognize short sequences of about 3 base pairs. By combining 6 to 8 of these fingers, scientists can target a specific sequence of approximately 20 base pairs.

\n\nAnother major class of tools is transcription activator-like effector nucleases (TALENs). Like ZFNs, TALENs use a non-specific DNA-cutting domain linked to specific DNA-recognizing peptides. The CRISPR-Cas system is perhaps the most famous modern method. Developed as a major advancement in 2015, the CRISPR/Cas9 system significantly improved the efficiency and practicality of large-scale genome editing. While earlier methods like meganucleases or ZFNs can be costly and time-consuming to design, CRISPR has made the process much more accessible. Researchers are even looking for alternatives, such as OMEGA proteins, which are endonucleases found in transposons.

\n\nThe history of this field shows a rapid progression in capability. Genetic engineering has been used to introduce new genetic elements since the 1970s. However, true genome editing began to emerge in the 1990s, though early efforts suffered from low efficiency. In 2011, Nature Methods named engineered nucleases as the Method of the Year. In 2015, Science magazine named CRISPR the Breakthrough of the Year. The field also faces significant ethical milestones. In 2019, the first humans were born from genome-edited embryos following a controversial affair involving scientist He Jiankui. This event led to calls for strict regulations regarding the manipulation of the human genome.

\n\nGenome editing has massive real-world significance across many industries. In agriculture, the Roslin Institute engineered pigs that are resistant to a virus causing porcine reproductive and respiratory syndrome. This disease costs pig farmers in the US and Europe approximately $2.6 billion every year. In food science, a tomato called Sicilian Rouge High GABA was approved for sale in Japan in 2020. This tomato contains more of an amino acid that may promote relaxation. In medicine, a 2020 US trial showed that CRISPR could be safely used on three cancer patients. These examples show how precise DNA changes can solve economic and health challenges.

\n\nBeyond simple edits, these technologies connect to complex biological systems and research. Scientists use homologous recombination (HR) to create transgenic mice with specific genes \"knocked out\" or "knocked in." This work was so impactful that Mario Capecchi, Martin Evans, and Oliver Smithies won the 2007 Nobel Prize in Physiology or Medicine. Researchers also use conditional targeting to study vital genes. By using systems like Cre-LoxP or Flp-FRT, they can switch genes on or off only in specific cells or at certain times. This allows for the study of gene functions without killing the organism prematurely. This deep level of control is essential for modern biological research and gene therapy.", "media": [ "File:Possibilities of genome editing.jpg", "File:DsDNA break repair and CRISPR-based genome editing.svg", "File:Engineered Nucleases.jpg", "File:MEGANUCLEASE-ZFN-TALEN-CRISPR-text-to-path.svg", "File:Overview of TALENs.png", "File:Endogenous genes targeted.jpg" ] }