dna crispr illustration

Gene editing with CRISPR-cas9

Introduction

Scientists have been finding ways to make human life trouble-free and valuable. They have tried to replace the bad traits with useful traits through selective breeding. But it sometimes did not show the desired results. Scientists figured out how it could be done after the discovery of DNA (deoxyribonucleic acid), a complex molecule that is responsible for our growth, traits, reproduction of anything alive. Four bases are paired in specific code that gives rise to a double helix structure called DNA carrying all our genetic information. If we change the sequence of the pairing of bases, we change the data, and the result is shown on the being carrying it.

Today we have pest-resistant crops, fast-growing salmon, injectable insulin, milk with additional protein, and also fluorescent zebrafish. These are genetically modified organisms. And it seems striking, gene editing was very intricate, high priced, and took a long time to show results. With the discovery of CRISPR, everything changed.  So what is CRISPR, and how it works? What is its application and why it has become a question mark on ethical values? Go through the article to know all these answers.

What is CRISPR?

Clustered Regulatory Interspaced Short Palindromic Repeats. It is a revolutionary technology that enables scientists to vary the DNA sequence to produce a new or desired outcome. CRISPR was first seen in archaea in the 1990s.  It was an essential part of their immune system, which protected them against bacteriophages. The archaea had a repeating sequence of genetic code interrupted by “spacer code”- remains of genetic code from past invader bacteriophage. It seems like the archaea have stolen the genetic code of bacteriophage and incorporated it with its genome. This system of genome helped create a memory that allows the cell to recognize and kill its invader if they ever return. 

How does CRISPR – cas9 works?

CRISPR “spacer” sequences are transcribed into short RNA sequences (“CRISPR RNAs” or “crRNAs”) capable of guiding the system to matching sequences of DNA. When the target DNA is found, Cas9 – one of the enzymes produced by the CRISPR system – binds to the DNA and cuts it, shutting the targeted gene off. Once the DNA is reduced, the cell’s natural repair mechanisms kick in and work to introduce mutations or other changes to the genome. There are two ways this can happen. According to Huntington’s Outreach Project at Stanford (University), one repair method involves gluing the two cuts back together. This method, known as “non-homologous end joining,” tends to introduce errors. Nucleotides are accidentally inserted or deleted, resulting in mutations, which could disrupt a gene. In the second method, the break is fixed by filling in the gap with a sequence of nucleotides. To do so, the cell uses a short strand of DNA as a template. Scientists can supply the DNA template of their choosing, thereby writing-in any gene they want, or correcting a mutation. 

Application of CRISPR

Greener Fuels:

bio diesel

Algae can produce biodiesel. But until now, the production of biodiesel was not viable, being too costly. “Synthetic Genomics” is a company that has created a strain of algae by using CRISPR, which can produce twice as much as fat, which could be used in synthesizing biodiesel. CRISPR allowed the scientist to remove the gene, which was responsible for the production of a limited amount of fats.

Eradicating pest

pest on leaf

Gene editing tool can be used to prevent spreading deadly disease which needs an animal vector. This can be done by creating “gene drives,” which will guarantee that genetic modification will be innate in all progeny spreading through an animal population.

Researchers at Imperial College of London experimented on a species of mosquito, responsible for malaria. They introduced a gene if both the parent carries this gene; the female won’t be able to lay eggs. In a trial with caged mosquitoes, the population vanished within four weeks.

Allergy-free food

food allergy

A vast percentage of the population is allergic to eggs, milk, wheat, peanuts. Sometimes these allergies are fatal. For example, there are four proteins in egg white responsible for allergies. CRISPR can help in rewriting those regions of genes that are recognized by an immune response causing the allergy. 

Pet breeding

zebra dog from crispr

Some breeds are prone to a particular disease. Like the Ragdoll cat is prone to kidney stones and hyperthyroidism, the German Shepherds and the Labrador Retrievers are prone to hip dysplasia. A pet owner would never want their adorable pets to suffer from diseases. By editing and removing the genes, we can help abolish the genetic defects found in the pure breed.

Decaf Coffee

instant coffee beans

A company in the UK called Tropic Biosciences has invented a variety of naturally decaffeinated coffee beans. Using CRISPR, the company has been able to shut down the genes responsible for seeds to produce caffeine. This might bring a positive result in the flavor, nutrition of coffee at an affordable cost.

Spicy Tomatoes

tomatoes

Chilli is spicy because it contains ‘capsaicin.’ By introducing the genes which produce capsaicin in tomatoes will make tomatoes tasty.

Designer babies

Designer babies just like another sci-fi fictions is close to becoming a reality

In 2018, a Chinese researcher, He jiankui, made headlines when he claimed that he had created the world’s first genetically-modified ‘designer babies,’ twins Lula and Nana.

The term ‘designer baby’ refers to a baby that has been given desired traits such as gender height and intelligence and multiple modifications by making changes to the genetic code (DNA). This can be done either by removing small sections of the existing genome or by introducing new segments of DNA into the genome of the sperm, egg, or embryo.

CRISPR  CLAIMS TO TREAT  MANY DISEASES LIKE:

Cancer

The Hangzhou Cancer Hospital takes out minute T-cells from the patients. By using CRISPR, it tries to modify T-cells by removing the gene that codes for PD-1. PD-1 is a protein that binds with the tumor cells and stops the immune cell from attacking. These modified cells are then injected into the patient with a strengthened capacity to fight the tumor cells.

Blindness

Some people are blind from birth. CRISPR is a great tool to treat genetic blindness. CRISPR cas9 can target and modify a single gene and can give sight to a blind man.

AIDS

There are many ways CRISPR can help in curing AIDS. One such way is to cut the DNA of the virus from its hiding place in the DNA of immune cells.

There is one more way; some people are born with a gene mutation, which makes them resistant to AIDS. This gene is called CCR5. CCR5 codes for a protein on the surface of immune cells, so that no more HIV could invade them. Now China carried out an extraordinary and controversial experiment by modifying the gene of an embryo. This raised ethical concerns, and hence China stopped this practice on embryos.

Various other ailments could be treated by using CRISPR, e.g. cystic fibroids, muscular dystrophy, sickle cell disease, and beta-thalassemia.

Ethical Concerns

As we know there are two sides of a coin, with these striking applications CRISPR raises ethical concerns like:

1.  How can we justify the extinction of a certain species just because it helps our human population?

2.  How will our ecosystem react to the extinction of a species, which other species will be able to compensate for this loss?

3.  Does the consent of parents are enough to grant a specific trait like height, blue eye color, muscular features to the baby?

4.  How can we differentiate between the good use and bad use of this revolutionary technology?

5.  Will it be the reason for discrimination between the CRISPR born and the natural-born individual?

6.  Will the high cost of gene therapy affect the part of the population who couldn’t afford it?

7. Is it okay to play GOD?

8.  If the modification is made in germ cells( embryo, egg, sperm cell), it will enable a change in all the upcoming progeny, what could be the result of this modified germline?

According to the biologist, genes are interdependent, so altering one gene of a cell may have irreversible effects on other genes or different characteristics of the body.

 a recent study by the Wellcome Sanger Institute found that that the use of CRISPR technology can lead to extensive genetic damage 

Conclusion

After knowing all about CRISPR. Its awe-inspiring application and its alarming ethical concerns. It cannot be overruled that it can do wonders in the healthcare sector. Many diseases can be cured, and various resources can be upgraded. But so are its ethical concerns it has the power to broaden the gap between rich and poor. Both ethical concerns and advantages cannot be neglected.

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