DNA fingerprinting

(a) Chromosomal DNA from two different individuals was subjected to traditional DNA fingerprinting. Their DNA appears as a series of bands on a gel. The dissimilarities in the patterns of these bands distinguish different individuals, much as the differences in physical fingerprint patterns can be used for identification. DNA evidence at a crime scene (E) matches suspect 2 (S2) but not suspect 1 (S1). (b) Automated DNA fingerprinting compares fluorescently labelled DNA sequences called short tandem repeat sequences (STRs), which differ in length among various individuals. A printout from the fluorescence detector is shown here.