Tracking new SARS-COV2 variants

Tracking new SARS-COV2 variants

Subject: Science and Technology

Context: Delhi-based CSIR-IGIB & scientists from various laboratories have been involved in the genome sequencing of SARS-COV2 variants in India. So far, over 50,000 sequences have been done from India, providing vital information about the mutations, and how they were spreading in the population.

What is a gene sequence?

• Genome sequencing is figuring out the order of DNA nucleotides, or bases, in a genome—the order of Adenine, Cytosine, Guanines, and Thymine that make up an organism’s DNA.
• The SARS-CoV-2 virus has certain genetic instructions that it uses to generate copies of itself. These instructions are coded in a sequence of 29,903 letters of RNA (ribonucleic acid bases – A, U, G, C) which make up what is known as the ‘genome’ of the virus.
• Sequencing the genome of the virus essentially means that we determine the sequence of the 29,903 letters of the virus. Approximately 50,000 genome sequences of SARS-CoV-2 have been assembled in India and more than 2.5 million genome sequences are available publicly from around the world.

How has genome sequencing helped?

• Genome sequencing helps us understand the evolution and spread of the virus and its
• It enables us to look closely at the mutations that arise in the virus during replication inside the human body after infection.
• Tracking such mutations can also allow the tracing of the origin and spread of a specific variant of the virus especially as variants spread across geographical areas.
• For example, the Delta variant predominated during the second wave in India.
• Multiple studies subsequently suggested that Delta is more transmissible as compared to other previous lineages of SARS-CoV-2.

How are the variants named?

• PANGO is a system of assigning names to different lineages of SARS-CoV-2 genomes, which was developed by virologists in the UK and Australia early in 2020.
• It is a hierarchical system of naming lineages.
• For example, the B.1.1.7 lineage, more commonly known as the Alpha variant, emerged from the lineage B.1.1 which had emerged from the lineage B.1, which is a direct descendant of the lineage B.
• The suffix can contain a maximum of 3 hierarchical levels, referred to as the primary, secondary and tertiary suffixes.