I am not a biologist therefore, it might seem as an elementary question. I retrieved rodent sequences from UTR database:
And I know there are supposed to be four nucleotides namely: A,G,C, and T. However, on this database I get sequences that have 'n' nucleotide in several locations, 'm' and 'k' as well. What does these letters mean? I haven't been able to find anything regarding it. Does it mean these positions in UTR are undefined or they are some 'intermediate' nucleotides if there are any?