Cytogenetics

Principle of FISH (Fluorescence In Situ Hybridization): FISH is based on the principle of hybridization, where a fluorescently labelled DNA or RNA probe is hybridized to a complementary sequence on a chromosome. This hybridization indicates the presence and location of the target sequence. This is done using a microscopic slide. Principle of Microarray: Microarrays utilize the principle of complementary base pairing. Fluorescently labelled, single-stranded DNA probes bind to a single-stranded DNA molecules on a microarray plate. This hybridization is detected to see the presence and level of expression of certain genes or DNA sequences. Applications of FISH: Diagnosis of genetic diseases by locating and identifying genetic aberrations like deletions, amplifications, and translocations. Locating specific DNA sequences on chromosomes. Identification of presence or absence of a particular gene. Studying translocation of genes on chromosomes by visualizing these translocations under a microscope. Applications of Microarray: To monitor the whole genome at once, to study gene expression patterns, to see the interactions of genes using a chip based assay. To compare the amounts of mRNA transcripts in cell populations, which can be useful in studying regulatory defects, cellular responses and cell cycle variations.