• GISH (genome in situ hybridization) is a cytogenetic technique for radio labeling portions of the genome within cells. 
  • GISH was created for plant breeding and animal hybrid cell lines. 
  • The GISH approach, which is an improvement on FISH, is commonly used to examine plants. 
  • GISH approaches aid in the differentiation of a cell’s genomes. 
  • Because this strong technique can discriminate genomes in hybrids, 
  • GISH is now being utilized to research hybrid cell lineages, genetic improvement programs, and polyploid evolution. 
  • GISH is a tool for analyzing meiotic behavior in hybrids and polyploids, which provides information about species relationships. 

The Main steps involved in the genomic in situ hybridization are: 

  1. Direct or indirect labeling of probe. 
  2. Blocking DNA fragmentation 
  3. Preparation of slide. 
  4. Denaturation of Probe and blocking DNA in a hybridization mixture. 
  5. Addition of the probe and the blocking DNA with the hybridization mixture. 
  6. Chromosome DNA denaturation. 
  7. Hybridization of blocking DNA and probe in the target sequence of the chromosome. 
  8. Detection of the probe in the chromosome of one parent. 
  9. Chromosome DNA molecule of the second parent related to the unlabeled blocking DNA. 
  10. Visualization of hybridization signals in a fluorescence microscope. Unlabeled chromosomes are visualized with a counterstain (blue). 

The major application of GISH technique are as follows: 

  1. Meiotic studies of chromosome. 
  2. Determination of phylogenetic relationship. 
  3. Determine the positions of translocation breakpoints in chromosome 
  4. Comparative genomic studies of malignant and normal cells of an individual 
  5. Identification of unknown genome 
  6. To identify the hybridized genome of crop varieties 
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