Biotechnology - DNA Fingerprinting

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  • 1. DNA FingerprintingBiotechnology
  • 2. DNA FingerprintingDeveloped by Alec Jeffreys in 1984 (Leicester,England)A method that identifies an individual based onthe patterns formed from the variations in thegenetic codeAlso known as DNA profiling, geneticfingerprinting, DNA typinghttp://3.bp.blogspot.com/-IAEoMaCBNXU/T-NqKxlVqLI/AAAAAAAAAFc/A8HPQXtOriE/s1600/fingerprint_1733878c.jpg
  • 3. First criminal case to employDNA fingerprintingColin Pitchfork arrested (1987) and convicted onthe rape and murder of 2 teenage girls (1983,1986) based on DNA fingerprintingFirst use of DNA fingerprinting to convict a criminalFirst to be caught as a result of mass DNA screening 5000 local men volunteered their DNA Ian Kelley was paid by Pitchfork to masquerade as himselfbut was later found outRichard Buckland was the prime suspectfirst to have innocence established with DNAfingerprinting
  • 4. DNA Fingerprinting: STR AnalysisUse PCR to amplify a fragment of interest that hasvariation in sizeFragment of interest is a specific loci on thechromosome that has short tandem repeats(STR)
  • 5. Short Tandem Repeats (STR)A type of variable number tandem repeats (VNTR)Short repetitive sequences, most commonly 4basesPolymorphic: many formsvariations in length due to the number of times thesequence repeats
  • 6. Example: Polymorphism atD10S1248 locusRepetitive sequence: GGAAAllelic variation: varies from 8-19 repeatsFragment size: varies from 235-271 bp when usingprimers5-GGAATAAGTGCAGTGCTTGG-35-ACCAATCTGGTCACAACCAT-3
  • 7. STR PolymorphismEach person will have 2 copies but the copies canbe different lengths (heterozygous) or the samelength (homozygous)
  • 8. Allelic Variation of STRNumber of alleles is very smallAllele shared by 5 - 20% of individualsWhat implications would this have?
  • 9. LociThe power of STRanalysis comes fromlooking at multipleSTR locisimultaneouslyIn North America, 13loci are amplified plusone (AMEL) todetermine sexhttp://upload.wikimedia.org/wikipedia/commons/7/7a/Codis_profile.jpgInfo on each locus can be found at:http://www.cstl.nist.gov/strbase/str_fact.htm
  • 10. LociIf all the loci present arehomozygous, how many lociare represented?If all the loci present areheterzygous, how many lociare represented?
  • 11. DNA Fingerprinting Procedure1. PCR: primers amplify the fragment of interest (an STRloci)2. Gel electrophoresis: separate fragments by size3. Visualize the gel
  • 12. DNA Fingerprinting ApplicationPaternity testing: identifying the fatherAnimation: http://www.sumanasinc.com/webcontent/animations/content/paternitytesting.htmlCriminal cases: eliminating suspectsIdentifying a corpseFood testing (i.e. Champagne, horse meat)
  • 13. PaternityUsed to identify achild’s parentsEach child inheritsone set ofchromosomes fromeach parent
  • 14. PaternityWhat is the differencebetween paternityinclusion versuspaternity exclusion?
  • 15. Paternity The chart shows 5 loci and the size of the fragmentsproduced through DNA fingerprinting of each individual. Is it likely that the alleged is the father of the child?Explain.DNA Marker Mother Child Alleged fatherD21S11 28, 30 28, 31 29, 31D7S820 9, 10 10, 11 11, 12TH01 14, 15 14, 16 15, 16D13S317 7, 8 7, 9 8, 9D19S433 14, 16.2 14, 15 15, 17
  • 16. PaternityIf lane 2 represents thebiological mother determinewhich lane represents thefather.Explain how you came to thisconclusion.
  • 17. Paternity Assuming C is a parent of B, who is the other parent (A1,A2 or A3)?
  • 18. PaternityCan individual A,B and C berelated (parentand child)?If so, who iswho?
  • 19. Criminal CaseWhich person ismore likely to besuspected in thecrime?
  • 20. Criminal CaseWhat does this DNAfingerprint tell you?
  • 21. Sexual AssaultCaseWhich DNA sampleswere collected at thecrime scene?Which DNA sampleswere taken after thecrime?Why was the husband’sDNA also taken?What do you think thecontrol was used for?
  • 22. Activity: DNA FingerprintingThe CASEA married couple arranged with a surrogate to have ababy. The woman’s egg was fertilized in vitro withher husband’s sperm and the developing embryo wasimplanted into the surrogate mother. When thesurrogate mother gave birth, she decided she wantedto keep the baby. She claimed that the developingembryo spontaneously aborted and the baby is thenatural child of herself and her boyfriend. The case istaken to court to decide custody. A strong piece ofevidence is DNA fingerprinting.