FISH: Fluorescence In Situ Hybridization

FISH FISH stands for Fluorescence in situ hybridization. FISH is a technique in the lab used to see where a DNA sequence or certain gene is located in an individual’s genome. This allows scientists to look for genetic conditions caused by alterations in chromosomes. FISH can be used to find distinct features in DNA for genetic counseling, species identification, and medicine. It can also be used to find certain RNA points in cells and tissue samples. FISH is used on blood samples or any other cell containing materials. How does FISH work? To identify certain genes the first step is to prepare probes. Probes are brief sequences of single-stranded DNA that matches the portion of the gene the scientist is looking for. Next, is to label the probes with colors of fluorescent dye. Originally, DNA is made up of two strands of similar molecules that bind to each other. The single-stranded probes are able to bind to that similar DNA strand, wherever it is on that person’s chromosomes. As the probe binds, scientist are able to track it by its fluorescent color tag. This will be visible under a microscope. There are three different types of FISH probes all with different uses. There are locus specific probes, alphoid or centromeric probes, and whole chromosome probes. Locus specific probes bind to a precise region of the chromosome. When
Each bind to different sequences along a chromosome. The probes labeled with different fluorescent colors, allow for the chromosomes to be labeled in special colors. According to the National Human Genome Research Institute, “the resulting full-color map of the chromosome is known as a spectral karyotype” (NIH, 2015). Spectral karyotype will result in chromosomes labeled in their metaphase stage. These particular probes are especially useful for determining abnormalities in chromosomes. There is also virtual karyotype which only detects gains and losses of chromosomal