Generating fingerprints
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DNA Fingerprint profiles are generated on automatic sequencers or in common gel electrophoresis chambers: a mixture of DNA fragments with different lengths migrate in an electric field through a gel matrix and are separated by length.

Shorter fragments run faster than longer ones. The fragments are detected usually by measuring a fluorescence signal coupled to the fragments and after having run a certain distance or time.

The detection occurs either by a CCD camera (or other detectors) as a continuous measurement (trace measurement) or after the complete run as a still image by a digital camera.

Figure 1. Image of a DNA fingerprint gel with a size standard (first lane) and eight fingerprint profiles. For one sample the trace profile is shown (blue line).

Data Format
The data is stored either as trace files or as image files (Tab. 1).

Table 1. Typical file formats generated by fingerprint analysis are:
File extension
Automatic capillary sequencers of the Prism series (Applied Biosystems Group, ABI).
Automatic sequencers of several manufacturers, e.g. Beckman Coulter.
Windows bitmap format used for saving images by some gel documentation systems.
An image format used by many gel documentation systems and also by automatic sequencers of LI-COR Biotechnology.
These and other image formats are used by many gel documentation systems.