Figure 1
From: Noninvasive prenatal diagnosis in a fetus at risk for methylmalonic acidemia
Schematic representation of the methodology. Both maternal blood and cell portions of cord blood (taken at birth) verify the genotype of all probes used for mutation status, fetal fraction, and haplotype determination. Plasma from the pregnant mother was split into three portions. Direct targeting of the c.322C>T (p.R108C) mutation was conducted with digital polymerase chain reaction (dPCR) to count the alleles in plasma directly and to provide a quantitative measure for the absolute amount of DNA in plasma (7,200 molecules used). Diverse single-nucleotide polymorphism (SNPs) (13) were targeted in a multiplex amplification to determine the fetal fraction (7,200 molecules used). Finally, a separate multiplex amplification of 11 targeted single-nucleotide variations for a haplotype linked to c.322C>T was performed on 24,000 molecules of input.
