13q123

13q12.3 is a cytogenetic band on the long arm of human chromosome 13. In standard karyotype notation, the designation refers to a specific sub-band within the distal portion of the q arm and is used to describe the location of genes and chromosomal abnormalities. The exact borders of the region can vary slightly depending on the genome build and the cytogenetic map used.

The region includes several genes, most notably BRCA2, a tumor suppressor involved in homologous recombination and DNA repair. BRCA2 mutations confer increased risk for breast and ovarian cancers and can influence treatment decisions. While BRCA2 is the most well-known gene in this area, other genes within or near 13q12.3 may also contribute to local gene regulation or disease susceptibility, depending on genetic context and structural variation.

Clinical significance: Alterations in 13q12.3 can contribute to cancer predisposition through BRCA2-related mechanisms, and somatic alterations in tumors can occur as part of broader genomic instability. Deletions, duplications, or rearrangements affecting this region may impact the function of BRCA2 or neighboring elements, with potential phenotypic consequences in some individuals.

Detection and research: Cytogenetic testing methods such as fluorescence in situ hybridization (FISH), array comparative genomic hybridization (array CGH), and sequencing can identify copy number changes and sequence variants in 13q12.3. The region is a focus of study in cancer genetics and in investigations of structural variation and genome stability.

See also: BRCA2, chromosome 13 regions, hereditary breast and ovarian cancer.