What information does FISH actually provide?

FISH provides information about the presence, location, and arrangement of specific DNA or RNA sequences within chromosomes or cells. It is important to note that metaphase FISH requires cells to be cultured and synchronized at metaphase to provide positional information, while interphase FISH does not provide positional information. Metaphase FISH is used visualizing specific regions of the genome and identifying insertions, deletions, or other rearrangements with precision determined by the probe used. FISH also allows researchers to map the genetic material inside of cells, particularly genes or parts of genes. Thus, FISH is used in chromosome painting, which can show the entire chromosome or specific segments (either in one color or with distinctive banding patterns) providing detailed information about chromosomal rearrangements. 3-D FISH is a technique developed to study how chromosomes and smaller regions within them are positioned and organized in the three-dimensional space inside cell nuclei. FISH is also commonly used to detect chromosomal abnormalities, helping to understand various genetic conditions or diseases (karyotyping). Additionally, FISH is used to count the number of human chromosomes.