Gene editing is a technology that enables the scientists to change the DNA of the organism. In this technology, the genetic material is added, removed or replaced at specific locations in the genes. The scientists have developed many approaches to edit the genes. The most recent approach is CRISPR-Cas9.
<center>![gene-editing-2375732_960_720.png](https://steemitimages.com/DQmQvV6rss4zDF8pNy9c3zqrZHhToE4oxN98dR4SeNNkpqK/gene-editing-2375732_960_720.png)</center> [image source: Pixabay](https://pixabay.com/en/gene-editing-crispr-dna-editing-2375732/)

Chinese scientists have started the human trials of gene editing technology known as CRISPR. As a trial, they injected CRISPR/Cas9 edited cells into 86 patients. This is the first time that CRISPR/Cas9 has been injected into humans. 

The CRISPR/Cas9 system basically consists of two molecules; Case9 which is DNA cutting enzyme and piece of RNA molecule which is used as a guide for that enzyme. The guide RNA is prepared by scientists and it is used to target specific DNA sequences. Cas9 enzyme follows guide RNA to the same location where the editing tool is located. It cuts the target DNA at specific places. In this way, scientists are able to replace the defective gene in the patient with the healthy gene.

<center>![GRNA-Cas9.png](https://steemitimages.com/DQmZysq7oYwq8Mf1MhFhXeEHfknQrAkWqXcsQ1GY64UAknr/GRNA-Cas9.png)</center> [Wikimedia Commons image](https://upload.wikimedia.org/wikipedia/commons/5/51/GRNA-Cas9.png)

CRISPR/Cas9 is basically a powerful gene editing tool that is used to edit the genes at specific locations. China is the first country that has used this gene editing system in humans. In this process, immune cells are removed from the cancer patient and then modified with gene editing tool. The function of CRISPR is that it turns off the gene which slows the immune response in cancer patients. The modified immune cells are placed back into cancer patients. China has also made trials on HIV patients using CRISPR. 

The trial results are yet not disclosed. USA has also approved the experiments using CRISPR in humans. In phase I, it is hoped that scientists will start clinical tests in patients having beta-thalassemia in this year. 

There are also other applications of CRISPR. It helps to block mutations which are caused by cancer and slows down its growth. It is also used to remove deadly mutations from human embryos. It is also used to correct muscular dystrophy in human cells. There are reports that it helped mice to recover from sickle cell disease.

<center>![DNA_Repair.png](https://steemitimages.com/DQmRssdVv6Lb4UTcf7m6QgVUtXSZcjwKW2h3ypno5PqpTXv/DNA_Repair.png)</center> [Wikimedia Commons image](https://upload.wikimedia.org/wikipedia/commons/0/0c/DNA_Repair.png)
The sequences of CRISPR were first discovered in 1987 in Escherichia coli bacteria. The bacteria use it to protect from various viral infections. 

This system has produced huge excitement in scientists because it is faster, cheaper, accurate and more efficient than other methods.

Gene editing can arise the ethical issues, because it is being used to alter the human genes. Although currently the gene editing is limited to somatic cells and can affect only certain tissues and can’t pass to future generations. However, if any changes are made in sperm or egg cells, could pass to next generations. This can bring many ethical problems as it is currently illegal to edit sperm and egg cells in many countries.
<center>![DQmTjUEWdmEvtQcJMueV3YTGnHVNweSGbfDAAEVnCRGPJm4_1680x8400.png](https://steemitimages.com/DQmTjUEWdmEvtQcJMueV3YTGnHVNweSGbfDAAEVnCRGPJm4/DQmTjUEWdmEvtQcJMueV3YTGnHVNweSGbfDAAEVnCRGPJm4_1680x8400.png)</center>

References: 

1- [Wikipedia](https://en.wikipedia.org/wiki/CRISPR)
2- [https://ghr.nlm.nih.gov/primer/genomicresearch/genomeediting](https://ghr.nlm.nih.gov/primer/genomicresearch/genomeediting)