Table 1. RefSeq accession numbers and molecule types.

Accession prefixMolecule typeComment
AC_GenomicComplete genomic molecule, usually alternate assembly
NC_GenomicComplete genomic molecule, usually reference assembly
NG_GenomicIncomplete genomic region
NT_GenomicContig or scaffold, clone-based or WGSa
NW_GenomicContig or scaffold, primarily WGSa
NS_GenomicEnvironmental sequence
NZ_bGenomicUnfinished WGS
XM_cmRNAPredicted model
XR_cRNAPredicted model
AP_ProteinAnnotated on AC_ alternate assembly
NP_ProteinAssociated with an NM_ or NC_ accession
XP_cProteinPredicted model, associated with an XM_ accession
ZP_cProteinPredicted model, annotated on NZ_ genomic records

a Whole Genome Shotgun sequence data.

b An ordered collection of WGS sequence for a genome.

c Computed.

From: Chapter 18, The Reference Sequence (RefSeq) Database

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