Genome editing (also called gene editing) is a group of technologies that give scientists the ability to change the body’s DNA. These technologies allow the addition, removal or modification of genetic material at specific places in the genome. Several approaches to genome editing have been developed. The recent is known as CRISPR-Cas9, which is short for regularly grouped intermittent short palindromic repeats and CRISPR 9 related protein. The CRISPR-Cas9 system has raised a lot of excitement in the scientific community because it is faster, cheaper and more accurate and more efficient than other existing genome editing methods.
CRISPR-Cas9 has been adapted from the naturally occurring genome editing system in bacteria. Bacteria capture DNA fragments from attacking viruses and use them to create segments of DNA called CRISPR arrays. CRISPR arrays allow bacteria to “remember” viruses (or closely related). If the viruses attack again, the bacteria produce RNA segments from the CRISPR matrix to target the DNA of the viruses. The bacteria then use Cas9 or a similar enzyme to cut DNA into pieces, which turns off the virus.
The CRISPR-Cas9 system works similarly in the laboratory. Scientists create a small RNA fragment with a short ‘lead’ sequence that attaches (binds) to a specific target DNA sequence in the genome. RNA also binds to the Cas9 enzyme. Like in bacteria, the modified RNA serves to recognize the DNA sequence, and the Cas9 enzyme cuts the DNA at the target site. Although Cas9 is the most commonly used enzyme, other enzymes (e.g. Cpf1) can also be used. After DNA excision, scientists use their own cell DNA repair machine to add or remove fragments of genetic material or make changes to DNA by replacing an existing segment with a non-standard DNA sequence.
Genome editing is important in the prevention and treatment of human diseases. Currently, most genome editing research is designed to understand diseases using cells and animal models. Researchers are still working to determine whether this approach is safe and effective for use in humans. It is being studied in a variety of diseases, including one gene disorder such as cystic fibrosis, hemophilia and sickle cell disease. He also hopes to treat and prevent more complex diseases such as cancer, heart disease, mental illness and human immunodeficiency virus (HIV) infection.
Ethical problems arise when genome editing using technologies such as CRISPR-Cas9 is used to change human genomes. Most of the changes introduced during genome editing are limited to somatic cells, which are cells other than eggs and sperm. These changes only affect certain tissues and are not passed down from generation to generation. However, changes made to genes in ova or sperm (germ cells) or embryo genes can be passed on to future generations. Editing the genome of an embryo cell and embryo involves a number of ethical challenges, including whether the use of this technology is acceptable to improve normal human characteristics (such as growth or intelligence). Based on ethics and safety concerns, it is currently illegal to edit the genome of an embryonic cell and embryo in many countries.
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