Trisomy 21–associated hypomethylation is detected early on in fetal MNC. (A) Heatmap representation of differentially methylated regions between Tri21 FL-MNC and control FL-MNC. Each row represents a genomic region, and each column represents a patient sample. (B) Volcano plot representing the comparison of Tri21 to control FL-MNC. The x-axis represents the difference in DNA methylation between the 2 groups, and the y-axis represents the statistical significance of the differences. Red dots denote DMRs with absolute log ratio difference >2 and FDR <5%. (C) Stacking barplots representing the relative proportion of chromosomes 21 (left) and 17 (right) in the whole array and the Tri21 FL-MNC DMRs. P values for Fisher test followed by correction for multiple comparisons using the Bonferroni method. (D) Heatmap representation of regions with at least 25% difference in methylation between Ts1Rhr and control CD41⁺ cells. Each row represents a genomic region, and each column represents a sample.