title: Molecular diagnosis of Down's syndrome.
abstract: OBJECTIVE
  To establish a new diagnostic method for Down's syndrome using polymerase chain reaction (PCR).
  
  
  METHODS
  DNA extracted from five healthy individuals and five Down's syndrome patients was amplified in six specific tetranucleotide repeat loci on chromosome 21 using PCR. An accurate diagnosis was made by analyzing allelic distribution at each locus.
  
  
  RESULTS
  All Down's syndrome patients were identified as having at least two loci with three alleles, while none of the healthy individuals had three alleles. In addition, when two alleles were identified for a particular locus in the Down's syndrome samples, it was more likely that the intensity ratio between the two alleles was close to 2:1.
  
  
  CONCLUSIONS
  The molecular method can provide a fast, accurate, and economical alternation for the traditional cytogenetic diagnostic method for Down's syndrome.
authors.affiliation: Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing 100006, China.
authors.forename: Shuyu
authors.initials: S
authors.lastname: Wang
authors.forename: Chanwei
authors.initials: C
authors.lastname: Jia
authors.forename: Guoqing
authors.initials: G
authors.lastname: Ren
authors.forename: Yanmin
authors.initials: Y
authors.lastname: Ma
authors.forename: Wei
authors.initials: W
authors.lastname: Lü
authors.forename: Feng
authors.initials: F
authors.lastname: Ding
authors.forename: Jian
authors.initials: J
authors.lastname: Han
mesh_terms: D020732:Cytogenetic Analysis / Q000379:methods*; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D016133:Polymerase Chain Reaction