How is DNA physically collected? What’s revealed? How is it matched to a database of people? And how are samples collected without contamination?
In: Biology
Once DNA is collected, a DNA profile must be created. One method is using STRs or ‘Short Tandem Repeats’. Basically, in our DNA we have repeating regions that do not code for a gene. For example, GCAGCAGCAGCA is an STR, with ‘GCA’ being the repeating unit. The length of these is unique to the person and his or her lineage. So lab techs take the DNA out of the cells they collected at the scene, and they amplify (increase the number of copies) of about 10 different STR regions. Then, they run it through a machine that sequences the regions and can tell how long that region is. Say, for example, you found a sample of DNA and took it to the lab for analysis. One of the STR regions you sequenced came out to be 300 units long. You have a suspect in custody and get a sample of his DNA. That same STR region in his DNA is only 120 units long. Well, the conclusion would be that this guy is NOT your killer.
Stuff like that. Sorry if that was a bit too complex!
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