Biotechnology - DNA FingerprintingPresentation Transcript
DNA FingerprintingDeveloped by Alec Jeffreys in 1984 (Leicester,England)A method that identifies an individual based onthe patterns formed from the variations in thegenetic codeAlso known as DNA profiling, geneticfingerprinting, DNA typinghttp://3.bp.blogspot.com/-IAEoMaCBNXU/T-NqKxlVqLI/AAAAAAAAAFc/A8HPQXtOriE/s1600/fingerprint_1733878c.jpg
First criminal case to employDNA fingerprintingColin Pitchfork arrested (1987) and convicted onthe rape and murder of 2 teenage girls (1983,1986) based on DNA fingerprintingFirst use of DNA fingerprinting to convict a criminalFirst 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 outRichard Buckland was the prime suspectfirst to have innocence established with DNAfingerprinting
DNA Fingerprinting: STR AnalysisUse PCR to amplify a fragment of interest that hasvariation in sizeFragment of interest is a specific loci on thechromosome that has short tandem repeats(STR)
Short Tandem Repeats (STR)A type of variable number tandem repeats (VNTR)Short repetitive sequences, most commonly 4basesPolymorphic: many formsvariations in length due to the number of times thesequence repeats
Example: Polymorphism atD10S1248 locusRepetitive sequence: GGAAAllelic variation: varies from 8-19 repeatsFragment size: varies from 235-271 bp when usingprimers5-GGAATAAGTGCAGTGCTTGG-35-ACCAATCTGGTCACAACCAT-3
STR PolymorphismEach person will have 2 copies but the copies canbe different lengths (heterozygous) or the samelength (homozygous)
Allelic Variation of STRNumber of alleles is very smallAllele shared by 5 - 20% of individualsWhat implications would this have?
LociThe power of STRanalysis comes fromlooking at multipleSTR locisimultaneouslyIn 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
LociIf all the loci present arehomozygous, how many lociare represented?If all the loci present areheterzygous, how many lociare represented?
DNA Fingerprinting Procedure1. PCR: primers amplify the fragment of interest (an STRloci)2. Gel electrophoresis: separate fragments by size3. Visualize the gel
DNA Fingerprinting ApplicationPaternity testing: identifying the fatherAnimation: http://www.sumanasinc.com/webcontent/animations/content/paternitytesting.htmlCriminal cases: eliminating suspectsIdentifying a corpseFood testing (i.e. Champagne, horse meat)
PaternityUsed to identify achild’s parentsEach child inheritsone set ofchromosomes fromeach parent
PaternityWhat is the differencebetween paternityinclusion versuspaternity exclusion?
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
PaternityIf lane 2 represents thebiological mother determinewhich lane represents thefather.Explain how you came to thisconclusion.
Paternity Assuming C is a parent of B, who is the other parent (A1,A2 or A3)?
PaternityCan individual A,B and C berelated (parentand child)?If so, who iswho?
Criminal CaseWhich person ismore likely to besuspected in thecrime?
Criminal CaseWhat does this DNAfingerprint tell you?
Sexual AssaultCaseWhich 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?
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.