Why Molecular Biology Labs Are Almost Always Stocked With Salmon Sperm DNA

Pipettes? Check. Centrifuges? Check. Microplates? Check. Gloves? Check. Salmon sperm DNA? Check.

Wait what?

There are a variety of machines, consumables, and safety equipment needed to operate a molecular biology lab. And yes, for the vast majority of labs, purified salmon sperm DNA is one of those essentials. Why?

One group of experiments commonly performed in molecular biology is called hybridization experiments. These include fluorescence in situ hybridization (FISH) experiments, in which researchers insert fluorescent DNA probes into samples that bind to specific chromosomal locations. When viewed under a fluorescence microscope, the probes radiantly illuminate the inner workings of an organism.

Other hybridization experiments include microarrays to see which genes are “on” or “off,” as well as southern/northern blotting to detect specific DNA or RNA on cell membranes. Each of these experiments is made more accurate with the use of a blocking agent, a substance that prevents the DNA probe from binding to places where it shouldn’t. In many cases, salmon sperm DNA serves as that key blocking agent. Scientists coat empty surfaces on membranes or plates with it. Their targeted DNA probes are then less likely to bind to those places by mistake.