“UC Berkeley researchers have made a major improvement in CRISPR-Cas9 technology that achieves an unprecedented success rate of 60 percent when replacing a short stretch of DNA with another”(Antonio Carusillo, PhD Candidate in Genetic Engineering (Marie Curie) at University of Freiburg (2018-present). This statistic shows that there is more of a chance to success but there is a chance to fail 40 percent but overall it will succeed which is why people are lenient about will it actually work or not, but as technology get better so will treatments to cure hard to pinpoint disease such as cancer, zika, or leukemia. Genome editing (also called gene editing) is a group of technologies that give scientists the ability to change an organism’s DNA. These technologies allow genetic material to be added, removed, or altered at particular locations in the genome. Several approaches to genome editing have been developed. A recent one is known as CRISPR-Cas9, which is short for clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9. The CRISPR-Cas9 system has generated a lot of excitement in the scientific community because it is faster, cheaper, more accurate, and more efficient than other existing genome editing methods.
CRISPR-Cas9 was adapted from a naturally occurring genome editing system in bacteria. The bacteria capture snippets of DNA from invading viruses and use them to create DNA segments known as CRISPR arrays. The CRISPR arrays allow the bacteria to “remember” the viruses (or closely related ones). If the viruses attack again, the bacteria produce RNA segments from the CRISPR arrays to target the viruses’ DNA. The bacteria then use Cas9 or a similar enzyme to cut the DNA apart, which disables the virus.
The CRISPR-Cas9 system works similarly in the lab. Researchers create a small piece of RNA with a short”guide” sequence that attaches (binds) to a specific target sequence of DNA in a genome. The RNA also binds to the Cas9 enzyme. As in bacteria, the modified RNA is used to recognize the DNA sequence, and the Cas9 enzyme cuts the DNA at the targeted location. Although Cas9 is the enzyme that is used most often, other enzymes (for example Cpf1) can also be used. Once the DNA is cut, researchers use the cell’s own DNA repair machinery to add or delete pieces of genetic material, or to make changes to the DNA by replacing an existing segment with a customized DNA sequence.
Genome editing is of great interest in the prevention and treatment of human diseases. Currently, most research on genome editing is done to understand diseases using cells and animal models. Scientists are still working to determine whether this approach is safe and effective for use in people. It is being explored in research on a wide variety of diseases, including single-gene disorders such as cystic fibrosis, hemophilia, and sickle cell disease. It also holds promise for the treatment and prevention of more complex diseases, such as cancer, heart disease, mental illness, and human immunodeficiency virus (HIV) infection.
Ethical concerns arise when genome editing, using technologies such as CRISPR-Cas9, is used to alter human genomes. Most of the changes introduced with genome editing are limited to somatic cells, which are cells other than egg and sperm cells. These changes affect only certain tissues and are not passed from one generation to the next. However, changes made to genes in egg or sperm cells (germline cells) or in the genes of an embryo could be passed to future generations. Germline cell and embryo genome editing bring up a number of ethical challenges, including whether it would be permissible to use this technology to enhance normal human traits (such as height or intelligence). As the technology continues to get better CRISPR could be used to correct the faulty DNA that’s responsible for genetic diseases like cystic fibrosis, sickle cell anemia, hemophilia and perhaps muscular dystrophy. As long as scientists can identify which mutation causes these diseases, they could, in theory, use CRISPR to find these genes, break them, and replace them with healthy versions.
Other researchers are experimenting with using CRISPR to take genes that work fine and make them even better. For instance, they’d like to make small alterations to genes in crops and livestock to create plants that need less water, or cows that build more muscle mass without requiring extra feed. Scientists in Japan were the first to discover CRISPR in the DNA of bacteria in 1987. In their attempts to study a particular protein-encoding gene in E.Coli, the researchers noticed a pattern of short, repeating, palindromic DNA sequences separated by short, non-repeating, “spacer” DNA sequences.
Over the next five years, researchers realized that these repeats were present in many bacteria and other single-celled organisms. In 2012, scientists coined the term CRISPR, short for “clustered regularly interspaced short palindromic repeats,” to describe the pattern.
For another decade, scientists hammered out the details of CRISPR. They figured out that the repeating DNA patterns, along with a family of “Cas” (CRISPR-associated) proteins and specialized RNA molecules, play a role in bacterial immune systems. They deemed the entire complex of DNA repeats, Cas proteins, and RNA molecules as the CRISPR/Cas system.
Here’s how CRISPR/Cas works in bacteria: When bacteria encounter an invading source of DNA, such as from a virus, they can copy and incorporate segments of the foreign DNA into their genome as “spacers” between the short DNA repeats in CRISPR.
These spacers enhance the bacteria’s immune response by providing a template for RNA molecules to quickly identify and target the same DNA sequence in the event of future viral infections. If the RNA molecules recognize an incoming sequence of foreign DNA, they guide the CRISPR complex to that sequence. There, the bacteria’s Cas proteins, which are specialized for cutting DNA, splice and disable the invading gene.
In the fall of 2012, a team of researchers led by UC Berkeley scientists Jennifer Doudna and Emmanuelle Charpentier announced that they had hijacked the bacteria’s CRISPR/Cas immune system to create a new gene-editing tool. Their CRISPR/Cas9 system involved CRISPR, a Cas protein called Cas9, and hybrid RNA that could be programmed to identify, cut, and even replace any gene sequence. By the start of 2013, research applying CRISPR/Cas9 to genetic engineering was underway.The CRISPR system is not completely reliable. It doesn’t work all the time, and it occasionally causes changes in genes that weren’t intended As mentioned previously, Cas9 can only recognise genetic sequences of around 20 bases long, meaning that longer sequences cannot be targeted. More significantly, the enzyme still sometimes cuts in the wrong place. Figuring out why this is will be a significant breakthrough in itself – fixing it will be even bigger. Then, of course, there’s the issue that CRISPR didn’t work terribly well in human embryos. This saying that Scientists need to discover what went wrong there, and what the difference is between the success in single cells and the more patchy results with embryos. Also that if
However, as the technology continues to get better CRISPR could be used to correct the faulty DNA that’s responsible for genetic diseases like cystic fibrosis, sickle cell anemia, hemophilia and perhaps muscular dystrophy. As long as scientists can identify which mutation causes these diseases, they could, in theory, use CRISPR to find these genes, break them, and replace them with healthy versions.Other researchers are experimenting with using CRISPR to take genes that work fine and make them even better. For instance, they’d like to make small alterations to genes in crops and livestock to create plants that need less water, or cows that build more muscle mass without requiring extra feed.