Site-Directed Nuclease (SDN) genome editing

Why in news?

• Recently, the Ministry of Environment Forests and Climate Change has ??exempted SDN1 and SDN2 genome-edited plants which are free of exogenous introduced DNA from the stringent regulations applicable on genetically modified or GM crops.

About Genome Editing:

• Genome 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.

About Site-Directed Nuclease (SDN) genome editing:

• Site-Directed Nuclease (SDN) genome editing involves the use of different DNA-cutting enzymes (nucleases) that are directed to cut the DNA at a predetermined location by a range of different DNA binding systems.
• 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.
• Three main SDN technologies currently in use include:
  • Meganucleases, Zinc-Finger Nucleases (ZFNs) and Transcription Activator Like Effector Nucleases (TALENs).

Three categories of SDN

• Depending on the nature of the edit that is carried out, the process is divided into three categories - Site-Directed Nuclease (SDN 1), SDN 2 and SDN 3:
• SDN 1 :
  • It introduces changes in the host genome’s DNA through small insertions/deletions without the introduction of foreign genetic material.
• SDN 2:
  • SDN 2 edit involves using a small DNA template to generate specific changes.
  • SDN-1 and SDN-2 do not use recombinant DNA, do not lead to the insertion of foreign DNA.
  • As such, they do not produce new plant varieties that fall under the scope of the GMO legislation.
• SDN3 :
  • This process involves larger DNA elements or full-length genes of foreign origin which makes it similar to Genetically Modified Organisms (GMO) development.

PRACTICE QUESTION:

Consider the following statements:

1. All the categories Site-Directed Nuclease genome editing involves insertion of foreign genetic material in to host DNA.

2. SDN-1 and SDN-2 do not use recombinant DNA

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer