Calling it as the encoded evidence because it’s made up of nucleotide and around 3000 million nucleotide are passed on from parents to offspring and codes for the character of a person. DNA is present in nearly every cell of our bodies, and we leave cells behind everywhere we go without even realizing it. Flakes of skin drop of blood, hair and saline. In case of forensic we frequently rely upon the use of small bits of DNA to link criminal to the crimes they commit. So how does it work? Why DNA? Nothing else? An overwhelming majority of human genome is identical which is called as junk DNA across all individuals. But there are regions of variations and these variations occur anywhere in the genome and are random.
These are called as short tandem repeats also called as STR. These are short DNA sequences repeat and are easily measured and compared between individuals. Example of STR is D75820 5-16 GATA repeats.These repeats are random and hence not only one loci or region containing STR is compared but rather numbers of regions are compared like the FBI use 13 loci and in India 9 loci containing STR is compared. This is due to the fact that based on the principle of independent assortment.