Op.Dr. Nurettin Türktekin
FISH (Flow cytometry In Situ Hybridization)

FISH (Flow cytometry In Situ Hybridization)

Fluorescence In Situ Hybridization Method FISH (Flow Cytometry In Situ Hybridization)

Flow cytometry in situ hybridization, or FISH for short, is a basic molecular biology technique used in genetic research and medical diagnosis to detect specific genetic elements or DNA sequences in cells or tissue samples.

In fluorescence in situ hybridization, the aim is to mark certain regions of the chromosome as a genetic examination technique. It uses a DNA probe specifically designed for the targeted DNA sequence. This probe can fully or partially match the targeted DNA region. When we look at the area of use in microbiology, it is seen that it is effective in the rapid identification of microorganisms at the family, genus, or species level from direct clinical samples or growths in cultures. It is also used in phylogenetic analyses of microorganisms in scientific articles. This method is considered an important technique in this respect.

Considering its general principle, the FISH method allows the identification of microorganisms in mixed media directly from clinical samples without recourse to culture methods using probes targeting rRNA. The main purpose of Fish techniques is to use fluorescent probes to mark certain regions of the chromosome.

What is Fish (Flow Cytometry In Situ Hybridisation)?

Fish (Flow Cytometry In Situ Hybridisation) is the most effective method for locating specific DNA sequences, diagnosing genetic diseases, gene mapping, detecting various types of cancer, or identifying genetic abnormalities. It can also be defined as a genetic examination technique that uses fluorescent probes to bind to specific DNA or RNA sequences. Flow cytometry is a method that uses light to measure the physical and chemical properties of cells.

DNA-DNA hybridization is a technique generally used in molecular biology to measure the genetic similarity of sequences in a DNA pool. Hybridization is used to determine the genetic distance between two species.

FISH, an important molecular biology technique today, is used to detect and monitor specific genetic material or DNA sequences in cells or tissue samples. A DNA probe designed specifically for a targeted DNA sequence matches the targeted DNA region completely or partially. It means "in situ" when analyzed as a concept. For example, cancer in situ means cancer in a single location. In such applications, it is important to recognize these concepts in order to understand the characteristics of the procedures.

Who is a suitable candidate for Flow Cytometry In Situ Hybridisation?

The Fish technique is a method used to detect genetic or chromosomal abnormalities and to monitor specific genetic elements. In general, these methods are applied to those at risk of genetic diseases. Fluorescence in situ hybridization fish methods can also be applied in pregnancy situations in order to ensure a healthy birth.

Candidates to whom the Fish (Flow Cytometry In Situ Hybridisation) technique can be applied can be briefly listed as follows:

  • Those at risk of genetic disease,
  • In the diagnosis of early-stage cancer,
  • Diagnosis of genetic diseases,
  • Recurrent miscarriages or children with genetic abnormalities,
  • Expectant mothers of advanced age,
  • Those undergoing IVF and fertility treatment, etc.

The FISH test can be considered for people who apply for IVF treatments, which are among the assisted reproductive techniques. The genetic health of embryos created with these techniques can be examined in more detail. With in situ hybridization applications, genetic compatibility can be determined and treatment success rates can be significantly increased.

Such tests are used for people suspected of having a genetic disease. After examining suitable candidates for FISH-Flow, their genetic status can be observed. By examining the genetic conditions with the in situ hybridization fish method, it can be ensured that people, especially those who will be applying assisted birth techniques, have healthier babies. 

How is the Fish (Flow Cytometry In Situ Hybridisation) Procedure Performed?

The stages in the FISH method proceed in a very comprehensive manner. The FISH method used in the completion of microorganisms consists of fixation, preparation of preparations and dehydration, hybridization, washing, and imaging stages. When in situ hybridization stages and applications are examined, it is seen that the process proceeds in detail.

It stands out as a special molecular biology technique that includes a series of laboratory steps. With this technique, certain genetic or chromosomal features can be analyzed and detected. This technique briefly consists of the following stages:

  • Fixation phase,
  • Preparation of preparations and dehydration stage,
  • Hybridisation phase,
  • Washing phase,
  • Imaging stage.

First, the cells or tissue samples to be examined are prepared for a special treatment. Afterward, processes such as permeabilization of cell membranes, fixation of cells, and DNA exposure are followed.

Another important stage is probe preparation. In this context, a DNA probe suitable for the region to be examined is prepared. This includes a DNA fragment that partially or completely matches the probe. It is applied with a fluorescent stain or fluorescent marker. There are many more detailed process steps when applying the fluorescence in situ hybridization technique. Therefore, a suitable laboratory environment and specialists are needed. 

What are the Advantages of FISH (Flow Cytometry In Situ Hybridisation)?

Among the advantages of the FISH method, the most important one is the examination and detection of genetic and chromosomal features. It is also important in terms of allowing the identification of mixed microorganisms in their natural environment. DNA forming human chromosomes is composed of millions of nucleic acids. In such applications, all elements are examined in detail and conclusions are reached.

The advantages of the FISH method, in which peptide nucleic acid and all other elements are examined in general, are briefly as follows:

It provides identification of microorganisms at the species level without the need for culture structuring.

  • It is a sensitive and highly specific method for detecting genetic changes.
  • Various genetic changes can be easily detected.
  • It usually gives results in a short time.
  • It can also be used in live cells or tissue samples.
  • It is a non-invasive diagnostic method and carries a low risk.

The main advantage of the Fish technique is that it is a powerful and flexible diagnostic tool for analyzing genetic and chromosomal characteristics. This technique should be applied by an experienced laboratory team. Op. Dr. Nurettik Türktekin provides expert support in Fish (Flow Cytometry In Situ Hybridization) applications with its wide range of clinical and laboratory facilities for accurate results and definitive diagnoses. 



Ovarian cysts are fluid-filled sacs or vesicles seen inside the ovary. Normally, during each menstrual period, a cyst called a follicle, which carries the egg cell and can reach 3 cm in size, forms in the ovaries. Then this cyst cracks and the egg is released. In young girls with ovulation problems, normal or physiological follicle cysts that cannot rupture can grow every month and reach 5-10 cm, while small numbers of 0.5-1 cm in size, which we call polycystic ovaries, can be seen in series. Apart from these functional cysts, benign or malignant ovarian cysts can also be seen in all age groups.

Except for the most common functional ovarian cysts, cysts can be benign or malignant tumoral cysts. In addition, as a result of infection, abscess-shaped cysts may occur, which is usually accompanied by pain and high fever.


Fluorescence In Situ Hybridisation (FISH) is a technique that allows the examination of cells or chromosomal DNA - RNA on the preparation by means of nucleic acid probes. DNA or RNA can be analyzed without disrupting the cell structure. In this respect, it has a very important place in genetic analyses today. The main purpose of this technique is to identify and monitor specific DNA sequences or genes on the genetic materials of an organism.

It is defined as a technique that enables the detection and display of nucleic acid sequences such as DNA and RNA in morphologically preserved chromosomes, cells, or tissue sections. It targets specific DNA sequences or genes and is used for visual monitoring. The basic principle is to mark the targeted DNA sequence or gene with a probe.

The FISH method is widely used in the diagnosis of genetic diseases, cancer research, monitoring of chromosomal abnormalities, and cytogenetic diagnosis. 

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