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Fluorescence In Situ Hybridization : Diagnosis-Benefits


 What Is Fluorescence In Situ Hybridization?

Fluorescence in situ hybridization (FISH), technique that employs fluorescent probes for the detection of unique deoxyribonucleic acid (DNA) sequences in chromosomes. FISH has a much better rate of sensitivity and specificity than different genetic diagnostic exams which includes karyotyping and consequently may be used to stumble on a variety of structural abnormalities in chromosomes, inclusive of small genetic deletions regarding just one to five genes. It is also beneficial in detecting slight-sized deletions consisting of those causing Prader-Willi syndrome, an extraordinary genetic disorder characterized through a rounded face, low forehead, and intellectual incapacity. FISH additionally gives outcomes more speedy than karyotyping due to the fact no mobile way of life is required.

What Is Fluorescence In Situ Hybridization
Fluorescence In Situ Hybridization

FISH is commonly used for preimplantation genetic prognosis (PGD) in the course of in vitro fertilization. PGD entails acquiring an unmarried cell from an embryo inside the blastocyst degree of development. This unmarried mobile can then be analyzed using FISH. One problem with the usage of FISH for PGD is that an unmarried cell is scant cloth for diagnosis; consequently, a large array of assessments cannot be accomplished. Similarly, if the test fails for any technical cause, it can not be repeated.

The classical cytogenetics used trypsin-Giemsa or fluorescent banding pattern for identity and characterization of different chromosomal abnormalities inclusive of polycentric chromosomes, ring chromosomes, or chromatid interchanges. Though chromosome banding strategies based totally on Giemsa staining revolutionized cytogenetic analysis, they did no longer grow to be famous due to constrained decisions regarding handiest >three Mb of DNA. Certain chromosomal aberrations including reciprocal translocations and inversions had been not without difficulty recognizable with Giemsa stain. Besides that these techniques are very time consuming, and interpretation of karyotype could be very cumbersome and unsure.

In situ hybridization techniques initially advanced through Joseph Gall and Mary Lou Pardue in Nineteen Sixties (Pardue and Gall 1969) and John et al. (1969) have proved to be effective tools for figuring out the chromosomal location of hybridized nucleic acid. Soon after that fluorescent labels quickly replaced radioactive labels in hybridization probes because of their more protection, stability, and simplicity of detection.

Early in situ research used radioactive RNA or DNA probes that were categorized with 3H or 135I, and the sites of hybridization were detected by using autoradiography. These strategies were effectively implemented to both animals and plant life. RNA probes may be designed for any gene or any sequence inside a gene for visualization of mRNA, long noncoding RNA and miRNA in tissues and cells. These probes, often derived from the fragments of DNA that have been isolated, purified, and amplified for use in the Human Genome Project, consist of approximately 20 oligonucleotide pairs and cover an area of forty–50 bp of target RNA. In 1982, a new technique was described to localize DNA sequences hybridized in situ to chromosomes. This technique applied a biotin-labeled analogue of thymidine (TTP) which may be included enzymatically into DNA probes by means of nick translation. The web sites of hybridization have been detected either cytochemically by means of using avidin conjugated to horseradish peroxidase, or fluorometrically by using the usage of fluorescein-classified antibodies. Compared to autoradiography this method decreased the time required for detection, stepped forward decision, and gave less non-unique history and chemically solid hybridization probes.

Besides that non-isotopic strategies were developed the use of DNA probes labeled with amino acetyl fluorene (AAF), mercuration, and sulfonation, which can be detected after hybridization through affinity reagents. Recently a very effective machine has been described that uses digoxigenin-categorized nucleotides detected with the aid of antibodies sporting fluorescent or enzymatic tags. The non-isotopic labeling techniques have also been successfully applied for detection of extraordinarily repeated DNA sequences in plant chromosomes. The non-isotopic detection of low- or unmarried-replica genes, but, has no longer been a success.

Chromosome painting – aggressive hybridization using whole chromosomes – precise libraries for chromosomes as probes and human genomic DNA as the competitor became one of the first packages of FISH (Fig. 16.1). It supplied severe and particular fluorescent staining of the human chromosome in metaphase unfold and interphase nuclei. A translocation t(nine;22)(q34;p11) turned into first recognized in human neoplasia leading to Philadelphia chromosome.

Fluorescence in situ hybridization (FISH) is the most convincing method for locating the precise DNA sequences, prognosis of genetic illnesses, gene mapping, and identification of novel oncogenes or genetic aberrations contributing to various types of cancers. FISH involves annealing of DNA or RNA probes connected to a fluorescent reporter molecule with specific target collection of sample DNA, which can be observed underneath fluorescence microscopy. The approach has these days been increased to allow screening of the entire genome simultaneously thru multicolor entire chromosome probe strategies which includes multiplex FISH or spectral karyotyping or through an array-primarily based technique the usage of comparative genomic hybridization. FISH has absolutely revolutionized the sector of cytogenetics and has now been identified as a dependable diagnostic and discovery device within the fight in opposition to genetic diseases.

Types of Genetic Testing

Fluorescence In Situ Hybridization : Diagnosis-Benefits

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