What is the difference between RefSeq accession prefixes?
The RefSeq accession prefix indicates the molecule type and method used to supply the record. Please see the description of RefSeq accession prefixes. NCBI Accession numbers that begin with the prefix XM_ (mRNA), XR_ (non-coding transcript), and XP_ (protein) are model reference sequences produced by NCBI’s Genome Annotation project. These records represent the transcripts and proteins that are annotated on the NCBI Contigs and they may be different from GenBank submissions for mRNAs and/or the curated RefSeq records (with NM,NR,NP accession prefixes). These differences may reflect real sequence variation (polymorphism), or errors (or gaps) in the available genomic sequence. These model RefSeq records should be used with caution, after comparing them to other available sequence information (Check the evidence viewer, BLink, Gene, or sequence neighbors). [more…
