![]() Unlike the original DNA fingerprinting method, DNA profiling does not use restriction enzymes to cut the DNA.As a result the DNA can be extracted from a wider range of biological samples, including blood, saliva and hair. STR analysis is incredibly sensitive so it only needs a tiny amount of someone’s DNA to produce an accurate result. DNA is extracted from a biological sample.Like minisatellites they are repeated many times throughout the human genome, for example ‘TATATATATATA’. Microsatellites, or short tandem repeats (STRs), are the shorter relatives of minisatellites usually two to five base pairs long.Modern-day DNA profiling is also called STR analysis and relies on microsatellites rather than the minisatellites used in DNA fingerprinting.Image credit: Genome Research Limited DNA profiling Illustration showing the steps in DNA fingerprinting. To compare two or more different DNA fingerprints the different DNA samples were run side-by-side on the same electrophoresis gel.When exposed to radioactivity a pattern of more than 30 dark bands appeared on the film where the labelled DNA was.The minisatellites that the probes have attached to were then visualised by exposing the nylon membrane to X-ray film.The probes only attach to the pieces of DNA that they are complementary to – in this case they attach to the minisatellites in the genome. ![]()
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