 In contrast, since even a monogenic disease can be caused by many different mutations within the affected gene, conventional PGD methods based on finding a specific mutation would require mutation-specific tests.Thus, PGH widens the availability of PGD to cases where mutation-specific tests are unavailable.PGH also has an advantage over fluorescence in situ hybridization (FISH) in that FISH is not usually able to make the differentiation between embryos that possess the balanced form of a chromosomal translocation and those carrying the homologous normal chromosomes.