DNA STR Typing

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DNA STR Typing
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Short Tandem Repeats

• In mammalian genomes have tandem repeats
• ATTCGATTCGATTCG
• There are currently over 10,000 published STR
  sequences in the human genome.
• These are usually junk DNA. Therefore the
  variations between individuals are significant.
• For example One particular STR may have form
  (gata)n, n may be from 10 to 20 across different
  individuals.

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D7S280

• D7S280 is one STR site of the 13 core STR sites
  in the CODIS standard.
• By designing a pair of primers, we can amplify
  the region and measure the length using gel
  electrophoresis.
• By using multiple STR sites, we can determine an
  individual with high confidence.

1 aatttttgta ttttttttag agacggggtt tcaccatgtt
ggtcaggctg actatggagt 61 tattttaagg ttaatatata
taaagggtat gatagaacac ttgtcatagt ttagaacgaa 121
ctaacgatag atagatagat agatagatag atagatagat
agatagatag atagacagat 181 tgatagtttt tttttatctc
actaaatagt ctatagtaaa catttaatta ccaatatttg 241
gtgcaattct gtcaatgagg ataaatgtgg aatcgttata
attcttaaga atatatattc 301 cctctgagtt tttgatacct
cagattttaa ggcc
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Combined DNA index system
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Promegas product
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Multiplex PCR

• Primers are designed to ensure that different
  sites fall in non-overlapping regions.
• Primers in different groups are labeled with
  different fluorescents.

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• As of May 2007, 177,870 forensic profiles and
  4,582,516 offender profiles have been accumulated
  in CODIS, making it the largest DNA databank in
  the world
• surpassing the United Kingdom's National DNA
  Database, which consisted of an estimated
  3,976,090 profiles as of June 2007.
• As of the same date, CODIS has produced over
  49,400 matches to requests, assisting in more
  than 50,343 investigations