| Accession prefix | Molecule type | Comment |
|---|---|---|
| AC_ | Genomic | Complete genomic molecule, usually alternate assembly |
| NC_ | Genomic | Complete genomic molecule, usually reference assembly |
| NG_ | Genomic | Incomplete genomic region |
| NT_ | Genomic | Contig or scaffold, clone-based or WGSa |
| NW_ | Genomic | Contig or scaffold, primarily WGSa |
| NS_ | Genomic | Environmental sequence |
| NZ_b | Genomic | Unfinished WGS |
| NM_ | mRNA | |
| NR_ | RNA | |
| XM_c | mRNA | Predicted model |
| XR_c | RNA | Predicted model |
| AP_ | Protein | Annotated on AC_ alternate assembly |
| NP_ | Protein | Associated with an NM_ or NC_ accession |
| YP_c | Protein | |
| XP_c | Protein | Predicted model, associated with an XM_ accession |
| ZP_c | Protein | Predicted model, annotated on NZ_ genomic records |
Detailed link here: http://www.ncbi.nlm.nih.gov/books/NBK21091/
