Based on the internet, consensus sequence is defined as the following. """ In molecular biology and bioinformatics, the consensus sequence (or canonical sequence) is the calculated order of most frequent residues, either nucleotide or amino acid, found at each position in a sequence alignment. It represents the results of multiple sequence alignments in which related sequences are compared to each other and similar sequence motifs are calculated. Such information is important when considering sequence-dependent enzymes such as RNA polymerase. """. So based on this definition, I thought that the consensus sequence might not exist. Is it correct? Many thanks in advance.
Yes, it's very well possible that what is put forward as the consensus sequence might not exist as such in nature.
Keep in mind there are several angles to this, consensus sequence might as well be 100% correct and existing, often you will not be able to tell. What I said is a very brief answer to a complex issue.