What is DNA Standard used for in a fingerprint?

Answer 1

The DNA strand of each organism has some sequence different from others, but there are some sequences which are known as "variable number tandem repeats" (VNTR), which are repeated many times in the DNA of an individual. These are basis of "DNA fingerprinting". DNA is cut with a restriction enzyme from the specific sites of these repeats. When the DNA of two samples are cut by these restriction enzymes, and run on gel electrophoresis, the band pattern can be matched or compared. Imagine what would happen if you got a sample of DNA from a crime scene and wanted to compare it with another sample, run years earlier or in Another Country. The gels would have been run at different times, by different people, under different conditions, so perhaps you could not be sure if the bands on the gel match or not. To solve this problem gels are run with both the samples and a reference material, which serves two purposes. Firstly it assures us that the gel has run correctly and that samples were treated correctly. Secondly it means we can determine what the bands of our test DNA mean by comparing them to the reference material. Sometimes the reference DNA is called the standard reference material (SRM) and we commonly used SRM2390 (for RFLP), SRM2391a (for PCR) and SRM 2392 (mitochondrial DNA) in DNA fingerprinting. So the skinny answer is that DNA standards are used to assure the quality and comparability of the test performed.