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Forensic DNA Profiling Forensic DNA profiling 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 STR analysis 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 CODIS loci 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 CODIS Loci Figure 12.14A Two representative STR sites from crime scene

DNA samples STR site 1 STR site 2 Crime scene DNA The number of short tandem repeats match Suspects

DNA The number of short tandem repeats do not match Figure 12.14B DNA profiles generated from two STR loci Crime scene DNA

Suspects DNA Longer STR fragments Shorter STR fragments STR analysis 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