About GeneCards GC Identifiers

GeneCards genes now have unique, informative and stable GeneCards identifiers (GC ids), provided by the GeneLoc Algorithm.

The id begins with GC, which is followed by the chromosome number, 'P' or 'M' for orientation (Plus or Minus strand), and approximate kilobase start coordinate.

For example: OXA1L, with GC id

GC14P022306

is on chromosome 14 on the plus strand, starting at 22306 kilobases

Genes that are currently placed on a specific chromosome, but whose exact location on the chromosome is not yet known, receive a modified GC id, consisting of the chromosome and strand information, followed by a '9', which indicates uncertain location, followed by a letter representing the specific contig containing the gene and the gene's kilobase position on that contig.

For example: HMX1, with GC id

GC04M9R0039

is on chromosome 4 on the minus strand of contig NT_086661, starting at 39 kilobases

Genes located on the alternative reference sequences (haplotypes--see NCBI for a full explanation) c5_H2 on chromosome 5, DR51/DR52/DR53/c6_COX/c6_QBL on chromosome 6, HSC_TCAG/CRA_TCAGchr7v2 on chromosome 7, or c22_H2 on chromosome 22 have a special GC id made up of the chromosome and strand information, followed by 'b' (c5_h2), 'd' (DR51), 'r' (DR52), 'e' (DR53), 'c' (c6_COX), 'f' (c6_QBL), 'h' (HSC_TCAG), 'f' (CRA_TCAGchr7v2), or 'a' (c22_H2), the chromosome and strand information, followed by the gene's approximate kilobase start coordinate.

For example: ENSG00000196744, with GC id

GC06Mc32536

is on chromosome 6 on the minus strand of c6_COX, starting at 32536 kilobases

Genes whose positional information includes only the chromosome need a further modified GC id, which includes the chromosome number, followed by 'U9', indicating lack of strand and positional information, followed by five digits, assigned sequentially.

For example: GUK2, with GC id

GC01U990078

is on chromosome 1. Its strand and position are currently unknown.

If an id needs to change in future versions because the previously reported position is refined, the superseded id remains associated with the gene, along with the new one, so it cannot be assigned to any other gene, and so that users can still find the gene by that id.