Fig. 4: Aneuploidy detection using spike-in samples.
From: Noninvasive prenatal diagnosis by genome-wide haplotyping of cell-free plasma DNA
(a) Maternally inherited trisomy 21 detected in spike-in DNA samples with 20% and 10% fetal fraction, respectively. In the 20% spike-in sample, maternal fetal allele ratio (FAR) values dropped around 10% and −10%, indicating an extra copy from the “fetus” on chromosome 21. Similarly, in the 10% FF, maternal FAR values were around 5% and −5%. (b) Validation of maternally inherited trisomy case using sequencing data from the proband. The copy-number plot (log2 ratio) indicated chromosomal copy number on chromosome 21, with black dot as log2 ratio of each target and red line as segmented value. The paternal and maternal reference allele ratio from chromosome 21 also deviates from standard reference allele ratio of 0.5 and the homologous recombinations are consistent with the result derived from spike-in samples.
