[Quantitative pyrosequencing of heterozygous single nucleotide polymorphisms for rapid diagnosis of Down's syndrome].
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.
Liu
Xi-qun
XQ
School of Basic Medical Sciences, Nanjing Medical University, Nanjing, Jiangsu, 210029 PR China.
Wu
Hai-ping
HP
Bu
Ying
Y
Zou
Bing-jie
BJ
Chen
Zhi-yao
ZY
Zhou
Guo-hua
GH
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*
D004247:DNA