 ABO blood typing  Lacks power of discrimination  RFLP analysis using minisatellite probes  High power of discrimination  Laborious  STR analysis  PCR-based  Highly discriminating  Fast  mt DNA analysis  PCR-based  Slow due to the need for sequencing

 Short tandem repeats (STRs)  Short nucleotide sequences that are repeated in tandem  Eg: CAGCAGCAGCAG or (CAG) n  Composed of different numbers of repeating units in individuals and  Compares the lengths of STR sequences at specific sites in the genome

 Combined DNA index system  Typically analyzes 13 different STR sites and the AMEL (amylogenin) locus  CODIS profile has 26 numbers, since each locus has two alleles  The probability of match between any two random people is 1 in 575 trillion  Exception: Identical twins

Figure 12.14A Crime scene DNA Suspect’s DNA STR site 1STR site 2 The number of short tandem repeats match The number of short tandem repeats do not match Two representative STR sites from crime scene DNA samples

Figure 12.14B Crime scene DNA Suspect’s DNA Longer STR fragments Shorter STR fragments DNA profiles generated from two STR loci

◦ All loci amplified at once: each primer set is labeled with a different fluorescent dye ◦ Fragments separated using capillary electrophoresis and read with a laser beam. ◦ No gel electrophoresis involved