Genetic testing focuses on DNA molecules that are packaged into threadlike structures called chromosomes. Gene mutations occur due to changes to the DNA sequence, chromosomal structure, or number of chromosomes. Genetic aberrations play an essential role in many genetic disorders and can be inherited from parents or occur spontaneously during embryonic development. With advances in human genetic research and analysis technologies, various types of causative genetic aberrations associated with disorders can be detected prenatal and postnatal thus providing valuable information to aid parents, physicians, and genetic counsellors in making the best decisions before and after birth. Although conventional cytogenetic remains the ‘gold standard’ for whole genome screening from a variety of prenatal and postnatal tissues, its use is restricted entirely to dividing cells. Problems are encountered while dealing with tissues like amniotic fluid, bone marrow etc. that yield a low mitotic index with poor quality metaphases. The advent of Fluorescent In Situ Hybridization (FISH) has been a boon in such cases, as it offers an unprecedented opportunity for analysis of non-dividing cells (interphase cells). Apart from this, FISH has the power to detect submicroscopic rearrangements and abnormal clone of small size and can be used on various tissues like buccal mucosa, blood and bone marrow slides or fixed pellets usually available can be used for FISH analysis.