title: [Quantitative pyrosequencing of heterozygous single nucleotide polymorphisms for rapid diagnosis of Down's syndrome].
abstract: OBJECTIVE
  To establish a method to detect Down's syndrome through quantitative pyrosequencing of the heterozygous single nucleotide polymorphisms (SNPs) on the chromosome 21.
  
  
  METHODS
  An improved allele-specific-amplification was used to screen heterozygous SNPs on the chromosome 21 from 84 normal samples. Pyrosequencing was used to quantitatively determine the ratio between the two alleles of a heterozygote, and the diagnosis of Down's syndrome was thus carried out based on the ratio.
  
  
  RESULTS
  By genotyping 84 genomic DNA samples from normal Chinese population, 6 SNPs with a relatively high level of heterozygosity were screened out. Heterozygote coverage of 92.9% was achieved by using a panel of 6 SNPs on the chromosome 21. Ten clinical samples from Down's syndrome patients were quantitatively determined by pyrosequencing, and 9 samples were accurately diagnosed by comparing the ratio of the two alleles. The pyrosequencing results showed that the ratio of the two alleles were 2:1 or 1:2 for the Down's syndrome patients.
  
  
  CONCLUSIONS
  The method has the advantage of a low cost, simple process, and time-saving operation and could be potentially applicable to the rapid diagnosis of Down's syndrome.
authors.affiliation: School of Basic Medical Sciences, Nanjing Medical University, Nanjing, Jiangsu, 210029 PR China.
authors.forename: Xi-qun
authors.initials: XQ
authors.lastname: Liu
authors.forename: Hai-ping
authors.initials: HP
authors.lastname: Wu
authors.forename: Ying
authors.initials: Y
authors.lastname: Bu
authors.forename: Bing-jie
authors.initials: BJ
authors.lastname: Zou
authors.forename: Zhi-yao
authors.initials: ZY
authors.lastname: Chen
authors.forename: Guo-hua
authors.initials: GH
authors.lastname: Zhou
mesh_terms: D000483:Alleles; D044466:Asian People / Q000235:genetics; D002891:Chromosomes, Human, Pair 21; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D005820:Genetic Testing; D006801:Humans; D007621:Karyotyping / Q000379:methods; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000191:economics / Q000379:methods*
chemical_list: D004247:DNA