The present invention is of interallelic epigenetic alterations in cells of cancer-stricken individuals which can be used for diagnosing cancer or cancer risk. In addition, the present invention is of interallelic epigenetic pattern alterations and/or interallelic replication pattern alterations in cells of a conceptus having imbalanced chromosome(s) or in maternal cells of the pregnant female carrying the conceptus, which can be used for prenatal diagnosis of chromosomal imbalances in the conceptus. Moreover, the present invention is of interallelic epigenetic pattern alterations and/or interallelic replication pattern alterations in cells of individuals having a chromosomal imbalance mosaicism which can be used for diagnosing chromosomal imbalance mosaicism, either prenatally or after birth.