DNA Fingerprinting

HISTORY:

– 1984 Alec Jeffery’s: University of Lester he wanted to find if you can tell people apart or related by using their DNA.

– How did he and his team do this?

1. They used VNTRs ( Variable Number Tandem Repeats)
2.  Repeating string of bases ( like the same word written along a long ) 10-80 bases long.
3. You inherit these VNTR’s  ( along with the rest of your DNA) from your parents.
4. However, the VNTR’s do occur in the non-coding region (don’t encode for proteins)  mutations and duplications  occur more in the VNTRs than in other parts of the DNA.
5. This means that a person is more likely to have a similar number of repeats to close relatives and similar length VNTRs.
6. Used with Lab assistant and his parents to test this system.
7. Commercialized in 1987.

2015

1. Short Tandem Repeats (STRs)
2. Similar to VNT’s but smaller and stand up better to the degradation of DNA over time.

So How Does it Work at a Crime Scene

1. DNA from crime scene is collected, extracted and purified.
2. Polymerase Chain Reaction (PCR) is used to isolate the STRs in the DNA.
3. PCR amplifies specific DNA Sequences (STRs)
4. The different length STRs are run through electrophoresis to be separated out.
5. The larger longer STR repeats are heavier and move more slowly through the gel.
6. DNA Fingerprint 
   http://https://missbakersbiologyclasswiki.wikispaces.com/file/view/Picture2.png/32638361/Picture2.png

7. Just one nanogram of DNA is usually a sufficient quantity to provide good data.

   The 13 core STRs vary in length from 100 to 300 bases, allowing even partially degraded DNA samples to be successfully analyzed.

   Depending on the complexity of the repeat unit, the different alleles of an STR can vary by as little as a single nucleotide.

   Because of the need to differentiate single-base differences, PCR products are typically resolved using automated DNA sequencingtechnologies with software that recognizes allele patterns by comparison to a known “ladder.”

   Making an STR Match

   

Norrgard, K. (2008) Forensics, DNA fingerprinting, and CODIS. Nature Education 1(1):35

Is DNA Fingerprinting Used Just For Crimes?

1. Paternity tests ( Maury)
2. Immigration
3. Missing persons
4. Animals

Still Confused?

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Resources:

“The FBI and DNA Part 2: More About the Nationwide System that Helps Solve Crimes.” The Federal Bureau of Investigation. N.p., 28 Nov. 2011. Web. 6 Feb. 2015. <http://www.fbi.gov/news/stories/2011/november/dna_112811>.

https://www.youtube.com/watch?v=AkBUriMK9u8. YouTube. Oxford Education, 30 Oct. 2014. Web. 6 Feb. 2015. <https://www.youtube.com/watch?v=AkBUriMK9u8>.

Norrgard, K. (2008) Forensics, DNA fingerprinting, and CODIS. Nature Education 1(1):35

“What Is CODIS?” National Institute of Justice. N.p., 16 July 2010. Web. 6 Feb. 2015.