CHROMOSOME SPECIFIC CASES

  　 constitutional ring chromosomes are a rare type of intra-chromosome structural abnormality with an estimated occurrence of 1 in 50,000 newborns. a ring chromosome is resulted from breakage and fusion at the telomeric or distal regions of both chromosome arms; this circular chromosome replaces one normal chromosome and presents unique mitotic behavior. structurally, ring chromosomes are divided into two types: a complete ring chromosome without loss of genetic materials by telomere-telomere fusion or an incomplete ring with distal or interstitial deletions and duplications by one or multiple fusion events constitutional ring chromosomes are rare orphan chromosomal disorders. to compile and curate cytogenomic and phenotypic findings of these rare disorders, a web-based interactive ‘human ring chromosome registry’ using microsoft access based relational