Objectives:
@EN Down syndrome is one of major chromosomal anomalies associated with mental retardation. Because the incidence of Down syndrome increases with the maternal age, a rapid and accurate method for prenatal diagnosis is necessary. Recent progress
in
molecular biological techniques made it possible to define the loci of chromosome 21 responsible to Down syndrome and various primers for the amplification of these loci were developed. This study was performed to devise and evaluate the method
for
detecting trisomy 21 by semi-quantitative polymerase chain reaction(PCR) of S-IOOB and small tandem repeat(STR) analysis of D21S11.
@ES Study design:
@EN PCR was performed with DNA template obtained from 20 normal samples(blood 10, amniotic fluid 10) and 12 trisomic samples(blood 10, amniotic fluid 2) with 32P-labeled D21S11 and SIOOB primers. After the PCR products for D21S11 locus were
electrophoresed in 6% urea polyacrylamide gel, followed by the exposure to X-ray film, the densities of signals were recorded by densitometer. Agarose gel(2%) electrophoresis for PCR products for SIOOB and IGF-I was performed and the relative
amounts of
them were determined by counting radioactivities in the products.
@ES Results:
@EN Analysis of D21Sll STR showed equivalent triplets in 4 cases and 8 cases of unequivalent doublets(1:2) in trisomy 21 group. Normal group showed singlet in 5 cases and equivalent doublets in 15 cases. In the analysis of SIOOB, the ratio of
SIOOB
to
IGF-I was the normal samples showed the ratio of about 1.0.
The D21Sll STR analysis distinguished more clearly betwen normal and trisomic samples. However, the analysis of BIOOS was less clear in quantitation. These methods gave a result within 24 hours.
@ES Conclusion:
@EN Prenatal diagnosis of trisomy 21 through STR analysis of D21Sll using PCR is an useful, innovative, accurate and rapid diagnostic method within 24 hours, and it can be used in preimplantation diagnosis.
|