G-quadruplex structures and CpG methylation cause drop-out of the maternal allele in polymerase chain reaction amplification of the imprinted MEST gene promoter. oleh Aaron J Stevens, Selma Stuffrein-Roberts, Simone L Cree, Andrew Gibb, Allison L Miller, Kit Doudney, Alan Aitchison, Michael R Eccles, Peter R Joyce, Vyacheslav V Filichev, Martin A Kennedy