RAPID DETECTION OF FETAL ANEUPLOIDIES
BY QUANTITATIVE FLUORESCENT-POLYMERASE
CHAIN REACTION FOR PRENATAL DIAGNOSIS
IN THE TURKISH POPULATION
Guzel AI, Yilmaz MB, Demirhan O, Pazarbasi A, Kocaturk-Sel S, Erkoc MA,
Inandiklioglu N, Ozgunen FT, Sariturk C
*Corresponding Author: Associate Professor Ali Irfan Guzel, Department of Medical Biology and
Genetics, Faculty of Medicine, Rize University, 53100, Rize, Turkey; Tel.: +90-464-212-30-09; Fax: +90-
464-212-30-15; E-mail: aliirfanguzel@hotmail.com
page: 11
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RESULTS
The distribution of 31 pathological cases out of
1874 samples were as follow: 47,XX,+21 (19.4%,
6/31), 47,XY,+21 (48.4%, 15/31) 48,XXX,+21
(3.2%, 1/31), 69,XXX (3,2%, 1/31), 47,XY,+13
(3.2%, 1/31), 47,XXY (9.6%, 3/31), 47,XXX (9.6%,
3/31), 45,X (3.2%, 1/31). The ratio of heterozygous
fl uorescent peak areas were close to 1:1 for normal
cases (Figure 1) and 1:1:1 or 2:1 for aneuploidies of
chromosome-specifi c STRs (Figure 2). At least two
informative results for each chromosome-specifi c
STRs were required to evaluate the prenatal diagnosis.
Aneuploidic QF-PCR results were validated
with cytogenetic analyses to complete the diagnosis.
No false-positive results were observed, and all the
pathological QF-PCR results were consistent with
the cytogenetic analyses. Fetal sex and chromosome
X and Y copy numbers were determined by amplifi
cation of the non polymorphic AMXY sequences
(generates chromosome X- and Y-specifi c products,
differing 6 bp in length) and SRY, and other X- and
Y-specifi c STRs (Table 1, Figure 1). These fi ndings
were also in agreement with the cytogenetic analysis
in all cases.
In cases with uninformative results that have
none or only one 1:1 ratio for a given chromosome,
extra reaction mixture containing two or more additional
STR primer sets specifi c for the chromosome
of interest, were employed in order to obtain informative
results. Maternal cell contamination was detected
by evaluating peak patterns in heterozygous
STRs as such, if there are three alleles and the sum
of the peak areas of the two smaller alleles is equal
to the largest peak area then the smaller of the two
alleles is regarded as the maternal contaminant. The MCC sample results were clarifi ed by comparing
the fetal STRs with maternal STRs obtained
from maternal blood DNA samples (Figure 3). The
X-specifi c product of the AMXY marker was found
to be duplicated in three males producing fl uorescent
peak areas in the ratio of 2 (for the X chromosome)
and 1 (for the Y chromosome), 47,XXY males. In
all X chromosome-related aneuploidies (one 45,X,
three 47,XXX, and three 47,XXY cases), the correct
diagnosis was achieved by using all of the X
chromosome-specifi c STR markers. The diagnosis
of Turner’s syndrome was based on the detection of
a single QF-PCR product for all the X chromosomespecifi
c polymorphic markers (data not shown).
Of all markers studied, X22 and DXYS218
had the highest frequency of heterozygosity, therefore,
regarded as the most informative markers.
As for chromosomes 13, 18 and 21, STR markers,
D13S258, D18S386 and D211414-1411 had
the highest heterozygosity, respectively (Figure 4).
In terms of additional chromosome markers studied,
which were employed to validate the results
obtained with regular STR markers having one or
none informative markers for a specifi c chromosome,
STR markers, D13S742, D18S858, D211412
and DX8377, had the highest heterozygosity for
chromosomes 13, 18, 21 and XY, respectively, in
our study population (Figure 5).
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