Fluorescence in situ hybridization (FISH)

Fluorescence in situ hybridization (FISH) is a molecular cytogenetic which is designed by Christoph Lengauer. The DNA chain on chromosomes are detected and localized by using the Fluorescence in situ hybridization. Fluorescent probes are used by these which would uniquely bind to those parts of the chromosome that shows a sequence complementarily of high degree. This binding is detected by fluorescence microscopy. In fact fluorescence in situ hybridization is a 20-year-old technology in localizing specific nucleic acids sequences. The important principles underlying in the fluorescence in situ hybridization are automatic data collection and analysis, high-sensitivity detection and simultaneous assay of multiple species. FISH can also be used as a powerful tool in identifying the location of a cloned DNA sequence on metaphase chromosomes.

Fluorescence in situ hybridization is commonly used by researchers to identify the position of a particular gene inside a chromosome. There are points to be followed for this. Firstly you need to prepare short length string of single-stranded DNA. This DNA would go with a fraction of the gene that has been researched. These are known as probes. The second step is to name these probes. You can do this by combining by the number of colors of fluorescent dye. DNA is a combination of two strands of corresponding molecules. These molecules bind to one another similar to chemical magnets. Binding a probe to a chromosome, allows the researchers to see the location through its fluorescent tag. 

Type of FISH probes 

Many scientists utilize three dissimilar types of FISH probes in their researches. These FISH probes have different application:
· Locus specific probes

These kinds of Fluorescence in situ hybridization probe are used to bind to a very specific and meticulous section of a chromosome. In fact this sort of probe is helpful mostly when researchers have separated a small segment of a gene. They might also want to conclude using these that, on which chromosome the gene is located.
· Centromeric repeat probes or Alphoid

These are the special type of probe which is generated from rhythmic sequences. These sequences might be found in the core of every chromosome. Scientists make use of these probes to find out the accurate amount of chromosomes that an individual has. Combining this probe with the locus specific probes, they can determine the misplaced genetic material of an individual from a meticulous chromosome.
· Whole chromosome probes

The third type of probes is the group of smaller probes. Each probe binds in a diverse sequence, this can be done along with the actual length of a particular chromosome. Using various multiple probes named with a combination of dissimilar fluorescent dyes, researchers can label every chromosome with its own sole color. The chromosome that we finally got full-color map is also called as the spectral karyotype. These entire chromosome probes which are collections of smaller probes are used for the examination of chromosomal abnormalities. For example, a section of one chromosome is connected to another chromosome.

Applications 

In today’s world Fluorescence in situ hybridization serves various important applications. Some of them are listed as follows:
· Identifying the positions of Genes
· To diagnose the Chromosomal Abnormalities
· “Paint” the Entire Chromosomes
· In Analyzing the Interphase Chromosomes
· Microdeletion syndromes
· Chromosome structural abnormalities can be characterized
· Aneuploidy detection
· FISH and cancer cytogenetic
· Gene mapping
· Comparative genomic hybridization
· Prenatal screening,
· Oncology
· Agriculture
· Clinical diagnosis.