FISHing

Hi there, this is my first ever blog so please keep that in mind while reading. I guess I will start with the first two questions that I had when I learned about FISH; what is FISH and why do I care? Fluorescence in situ hybridization (FISH) is a laboratory technique for detecting and locating a specific DNA sequence on a chromosome. The technique relies on exposing chromosomes to a small DNA sequence called a probe that has a fluorescent molecule attached to it. The probe sequence binds to its corresponding sequence on the chromosome.(http://ghr.nlm.nih.gov/glossar y=fluorescentinsituhyb ridization). FISH is used by geneticists in order to diagnose abnormalities within chomosomes, which can save lives. That is why I care. I am a little nervous about attempting this project because it takes extreme precision and requires that measurements be conducted at specific times. I am super excited and ready to get started!

 

Figure 1: Principles of fluorescence in situ hybridization (FISH).

(a) The basic elements of FISH are a DNA probe and a target sequence. (b) Before hybridization, the DNA probe is labeled by various means, such as nick translation, random primed labeling, and PCR. Two labeling strategies are commonly used: indirect labeling (left panel) and direct labeling (right panel). For indirect labeling, probes are labeled with modified nucleotides that contain a hapten, whereas direct labeling uses nucleotides that have been directly modified to contain a fluorophore. (c) The labeled probe and the target DNA are denatured. (d) Combining the denatured probe and target allows the annealing of complementary DNA sequences. (e) If the probe has been labeled indirectly, an extra step is required for visualization of the nonfluorescent hapten that uses an enzymatic or immunological detection system. Whereas FISH is faster with directly labeled probes, indirect labeling offers the advantage of signal amplification by using several layers of antibodies, and it might therefore produce a signal that is brighter compared with background levels.

© 2005 Nature Publishing Group Speicher, M. R. et al. The new cytogenetics: blurring the boundaries with molecular biology. Nature Reviews Genetics 6, 784 (2005). All rights reserved.