Gene Editing vs GMO (genetically modified organism)

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Gene Editing:

Gene editing is a newer technique that is used to make specific and intentional changes to DNA. Gene editing can be used to insert, remove, or modify DNA in a genome. All gene editing technologies involve an enzyme known as a nuclease for cutting the DNA, in addition to a targeting mechanism that guides the enzyme to a specific location on the DNA strand (i.e., a gene within the genome). Gene editing has traditionally involved the insertion, removal, or modification of a single gene, but with CRISPR-Cas9 multiple genes can be targeted simultaneously. Such multi-gene editing is generally referred to as genome editing.

CRISPR-Cas9:

CRISPR is an acronym for “clustered regularly interspaced short palindromic repeats,” which are unique DNA sequences found in some bacteria and other microorganisms. These sequences, along with the genes that are located next to them, known as CRISPR-associated or Cas genes, form an immune system that protects against viruses and other infectious DNA. The CRISPR system identifies, cuts, and destroys foreign DNA.

CRISPR-Cas9 is a gene editing technology that uses a combination of (1) an enzyme that cuts DNA (Cas9, a nuclease) and (2) a guiding piece of genetic material (guide RNA) to specify the location in the genome. Generally, the guide RNA targets and binds to a specific DNA sequence, and the attached Cas9 enzyme cleaves both strands of DNA at that site. This cut can be used to insert, remove, or edit the DNA sequence. The cut is then repaired and the changes incorporated. This specificity of modification is one feature that differentiates CRISPR-Cas9 from predecessor genome editing systems.

What Are Gene Drives?

A gene drive is a system of biasing inheritance to increase the likelihood of passing on a modified gene. Offspring inherit one copy of each gene from its parents. Normally, this limits the total incidence of mutations over generations. Gene drive components cause the modified DNA to copy itself into the DNA from the unmodified parent. The result is the preferential increase in a specific trait from one generation to the next and, in time, possibly throughout the population.

GMO (genetically modified organism) :

A GMO (genetically modified organism) is a plant, animal, or microorganism that has had its genetic material (DNA) changed using technology that generally involves the specific modification of DNA, including the transfer of specific DNA from one organism to another.

Scientists have used a number of techniques in order to produce genetic changes in animals. These include the mutation of genes with radiation, chemicals and viruses, and are outlined below. The term ‘genetically modified organism’ (GMO) usually applies to an organism whose genetic material has been altered in a way that does not occur naturally by mating and/or natural recombination of its genes (see Annex C). It should be noted that, even though this definition seeks to draw a sharp distinction between artificial and natural processes, mutation of specific genes occurs spontaneously under natural conditions.

In India, Government has exempted certain types of genome edited crops from the stringent regulations applicable on genetically modified or GM crops thus giving a big boost to their further research and development. The ministry of environment and forest has exempted SDN1 and SDN2 genome edited plants from Rules 7-11 of the Environment Protect Act (EPA) for manufacture, use or import or export and storage of hazardous microorganisms or genetically engineered organisms or cells rules-1989.

This exemption is applicable to genome-edited plants, or organisms without any “foreign” genes in them.

 SDN stands for Site-Directed Nuclease (SDN) technology.

Three main SDN technologies currently in use include: Meganucleases, Zinc-Finger Nucleases (ZFNs) and Transcription Activator Like Effector Nucleases (TALENs).  They uses site directed nucleases ( SDNs ) to make changes that may either be a small deletion, a substitution or the addition of a number of nucleotides. Such targeted edits result in a new and desired characteristic.

The goal of SDN technology is to take advantage of the targeted DNA break and the host’s natural repair mechanisms to introduce specific small changes at the site of the DNA break

SDN applications are divided into three techniques: SDN-1, SDN-2 and SDN-3:

SDN-1 produces a double-stranded break in the genome of a plant without the addition of foreign DNA. The spontaneous repair of this break can lead to a mutation or deletion, causing gene silencing, gene knock-out or a change in the activity of a gene.

SDN-2 produces a double-stranded break, and while the break is repaired by the cell, a small nucleotide template is supplied that is complementary to the area of the break, which in turn, is used by the cell to repair the break. The template contains one or several small sequence changes in the genomic code, which the repair mechanism copies into the plant’s genetic material resulting in a mutation of the target gene.

SDN-3 also induces a double-stranded break in the DNA, but is accompanied by a template containing a gene or other sequence of genetic material. The cell’s natural repair process then utilizes this template to repair the break; resulting in the introduction of the genetic material.

https://sgp.fas.org/crs/misc/R44824.pdf

https://www.fda.gov/food/consumers/agricultural-biotechnology

https://royalsociety.org/-/media/Royal_Society_Content/policy/publications/2001/10026.pdf

https://www.hindustantimes.com/india-news/rules-relaxed-for-some-gene-edited-plants-organisms-101648665945313.html

https://www.business-standard.com/article/economy-policy/central-govt-exempts-genome-edited-crops-from-stringent-gm-regulations-122033001454_1.html

https://biotech.co.in/sites/default/files/2022- 02/FAQ%20about%20gene%20edited%20plants.pdf

http://www.nbtplatform.org/background-documents/factsheets/factsheet-site-directed-nucleases.pdf

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