In this so-called electrophoresis, the speed with which the DNA copies migrate can be used to infer their length. Therefore, the sample obtained after amplification is sent through a narrow mesh network in which the smaller copies move faster than the larger ones. STR segments differ in length and so do their PCR-generated copies. The DNA copies are then bound to a fluorophore to make them visible in the next step. To do this, scientists use the polymerase chain reaction (PCR): millions of copies of the STR sections can be produced in a few hours. Because the amount of DNA obtained from these samples is very small, it is first necessary to amplify the DNA in order to be able to analyse it. The analysis starts with the extraction of DNA from a sample (usually saliva). Instead, it determines the length of individual DNA segments, and in doing so reveals much about ancestry. They are as individual as a fingerprint and allow people to be identified almost uniquely (with the exception of identical twins).Ī paternity test is not a genetic test, because it provides little information about inherited genes. The sequence “GATC”, for example, may appear eight times in one person, but fifteen times in another. STRs are made up of between two and seven DNA bases that can be repeated many times. Scientists refer to these repeats as short tandem repeats (STRs). Paternity tests are based on the analysis of these repetitive regions of DNA. In these regions we find, among other things, sections full of repeats: short sequences of DNA bases that are always strung together in the same way. In our DNA we find coding regions, the genes, which account for only 2% of our entire genome, and non-coding regions. We inherit half of our genetic material from our father and half from our mother. By comparing the genetic profiles obtained from two individuals, the relationship between them can be determined. Paternity and kinship tests consist of an analysis of the DNA of each individual to obtain the so-called genetic profile or genetic fingerprint.
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