DNA markers are specific portions of DNA that have been determined by scientists to be useful for human identification. Usually, DNA markers consist of short, repeating sequences of DNA. The number of repeats in these markers are highly variable among individuals—this makes the markers effective for human identification purposes. A standard set of 13 DNA markers called the core CODIS loci is used all over the world as a human identification standard. Beta Paternity routinely tests 16 markers, and more as needed, for more conclusive results.