questions about DNA fingerprinting

[tracyliu]

In DNA fingerprinting, when u amplify the STRs by PCR, how how do you control the elongation of the primer so that the elongation stops exactly at the end of the STR?

[JackBean]

exactly as in any other PCR - you don't. But by use of two primers, you exponentially amplify those short fragments, while the longer grow only linearly. Look up to PCR principle