Which device is used to separate DNA fragments based on their length?

The method of gel electrophoresis is specifically designed to separate DNA fragments based on their length. In this process, an electric field is applied to a gel matrix, typically made of agarose or polyacrylamide, which allows the negatively charged DNA molecules to migrate towards the positive electrode. Smaller DNA fragments move through the gel more easily and travel further than larger ones, resulting in a separation that can be visualized after staining.

This technique is fundamental in molecular biology for applications such as DNA fingerprinting, cloning, and analyzing PCR products. It provides valuable insight into the size of the DNA fragments, which is crucial for various genetic analysis and manipulation tasks.

Other devices listed have different primary functions: a centrifuge is used for separating components in a solution based on density, a thermocycler is essential for amplifying DNA during the PCR process, and a microspectrophotometer is useful for measuring the concentration of nucleic acids but does not perform separation based on size. Therefore, gel electrophoresis is the appropriate choice for separating DNA fragments by length.