Chromosome Fragile Site

**Semantic type:** Anatomical Abnormality|Cell or Molecular Dysfunction|Nucleotide Sequence

**Definition:** Heritable sensitive regions of chromosomes which show up in vitro as non-staining bands. They are associated with chromosome breakage and other aberrations. No abnormal phenotype has been definitely identified with autosomal fragile sites, but some rare autosomal recessive disorders may be due to homozygosity for fragile sites. A fragile site on the X chromosome is associated with Fragile X Syndrome. Fragile sites are designated by the letters "fra" followed by the designation for the specific chromosome and locus.

**Synonyms:** - FRAGILE SITE - Fragile Site