Abstract
This study aimed to determine the genetic alterations in the Omicron variants compared to other variants of concern (VOCs) to trace the evolutionary genetics of the SARS-CoV-2 variants responsible for the multiple COVID-19 waves globally. The present study is an in silico analysis determining the evolution of selected 11 VOCs compared to the original Wuhan strain. The variants included six Omicrons and one variant of Alpha, Beta, Delta, Gamma, and Mu. The pairwise alignment with the local alignment search tool of NCBI Nucleotide-BLAST and NCBI Protein-BLAST were used to determine the nucleotide base changes and corresponding amino acid changes in proteins, respectively. The genomic analysis revealed 210 nucleotide changes; most of these changes (127/210, 60.5%) were non-synonymous mutations that occurred mainly in the S gene (52/127, 40.1%). The remaining 10.5% (22/210) and 1.9% (4/210) of the mutations were frameshift deletions and frameshift insertions, respectively. The frameshift insertion (Ins22194T T22195G) led to frameshift deletion (Δ211N). Only four mutations (C241T, C3037T, C14408T, and A23403G) were shared among all the VOCs. The nucleotide changes among Omicron variants resulted in 61 amino acid changes, while the nucleotide changes in other VOCs showed 11 amino acid changes. The present study showed that most mutations (38/61, 62.3%) among Omicron variants occurred in the S gene; and 34.2% of them (13/38) occurred in the receptor-binding domain. The present study confirmed that most of mutations developed by Omicron variants occurred in the vaccine target gene (S gene).