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Transcript of Genetic Fingerprinting
Composition Disease Diagnosis 1900 Karl Landsteiner and ABO Blood Typing First Genetic Marker to be used in forensics 1:10 Power of Discrimination Told us why some blood transfusions worked and others didn't The idea of distinguishing people by their genetic characteristics was an idea that had been circulating before Genetic Fingerprinting was invented 1927 MN Blood Groups 1937 The Rhesus Factor Blood Typing Revolutionary for forensics, identification, and immunization Suspects AB+ A- 0+ AB+ AB- B- O- Karl Landsteiner and Alexander Weiner 1983 Kary Mullis and the PCR 1984 Alec Jeffreys discovers Restriction Length Polymorphism 1980's Discovery of microsatellites or Short Tandem Repeats DNA The human genome consists of 46 paired chromosomes, 23 from each parent Only 1-2% code for proteins GENES The rest are often just filling, consisting of repetitive sequences in organized clusters Repetitions and Loci Locus
location on the DNA, its specific position or place on a chromosome AACCGAGAAACCGAGA TTYUAGGAGG People have the same "words" in the same loci. Variations are found in the number of time these words are repeated AACCGAGAAACCGAGA Allele
Each sequence with a specific number of repeated nucleotides core sequence They can arise out of mutations - since are allowed to take place in these regions - or crossing over The number of repeats can distinguish one person from another Restriction Fragment Length Polymorphism At the University of Leicester, Sir Alec Jeffreys was studying microsatellites Variable Number of Tandem Repeats (VNTRs) a repeating string of letters 10-60 base pairs in length 13bp He used restriction enzymes to get restriction fragments from sister chromatids A B C Same loci, different alleles How he studied VNTRs Restriction
Enzymes Gel Electrophoresis DNA obstacle course, multiple restriction fragments are pulled toward + since DNA has a - phosphate backbone Southern Blotting DNA is transferred to a membrane X-Ray Results Press an X-Ray film onto it, and have it developed Lab Tech Stranger LT's
Mom Genetic Fingerprint the analysis of repetitive sequences at several DNA loci. Also called genetic profiling. VNTRs began to be used as genetic markers. They were reliable and useful for a range of tasks Power of Discrimination:
4 different VNTRs with enough repeats (15-41) 1: 1 million Short Tandem Repeats microsatellites: multi-loci 2-6bp in length scientists have compiled a list of core STRs that have non-overlapping allelic distributions convenient Withstand degradation better, need only a few cells PCR Used a thermocycler to amplify his lab technician's DNA A B C He noticed there was length polymorphism: when distance between nucleotide sequences differ because of the VNTRs Process: Collecting DNA Sample Blood, hair, saliva Gel Electrophoresis Capillary Electrophoresis Genetic Fingerprint If we only analyze 1 STR, the chance of two unrelated people having the same PCR-based genetic fingerprint is high - 1:2 and 1:100 STRs have fewer alleles and lower heterozygosity than VNTRs. To overcome it, we analyze multiple STRs simultaneously
16 STRs = power of discrimination 1:10 billion For Relationships who's the daddy For Health Homozygous and Heterozygous Case Studies Crime Cases In the famous case of OJ Simpson, who was charged with murdering his ex-wife Nicole Brown Simpson and Ron Goldman, defense attorneys successfully made a case for cross-contamination of DNA samples due to poor handling procedures. OJ Simpson DNA contamination In a nutshell, they argued that because the blood samples collected by the Los Angeles Police Department were taken with wet swatches and left in a hot truck for several hours, resulting in degradation. In addition, the defense also successfully argued that criminologists for the LAPD were, in general, poorly trained when it came to sample handling, did not follow standard protocol, did not take precautionary measures, and made serious errors when collecting samples. Their arguments were successful In 1985, former Marine Kirk Bloodsworth was convicted and sentenced to death for the rape and murder of a nine year old girl named Dawn Hamilton.
After several years of fighting for a DNA test, samples from the scene of the crime were sent to a lab for tests. The final reports concluded that the DNA found at the scene of the crime did not match Bloodsworth's DNA, and he was released and pardoned by the Governor of Maryland shortly thereafter. Bloodsworth's ordeal lasted 9 years, including two years on death row. The DNA did match that of Kimberly Shay Ruffner, and on May 20, 2004, he pleaded guilty to the crime for which Bloodsworth was convicted. Kirk Bloodsworth Wrongful Conviction Whodunnit???? Suspect DNA samples were taken from a crime scene, the female victim and two suspects in a sexual assault case. The victim’s boyfriend was also tested. Can you determine which suspect is likely the criminal? Crime Scene Precautions
DNA from a crime scene is frequently dirty. There is generally some contamination from the outside environment. If the crime scene is old, the DNA evidence might have degraded, or broken down, and if there was more than one person at the scene, the sample might be a mixture of more than one person’s DNA.
Just because someone’s DNA is found at a crime scene does not mean that they committed the crime. The DNA ladders are used to judge the sizes of the DNA fragments. Control samples are also run, to ensure that the experiment is done correctly. IDENTIFICATION Mystery of the Russian Royals Solved! In 2009, the bodies of the Russian Royal Family were identified after skeletons were found burried in the woods of Ekaterinburg. DNA from Queen Elizabeth II's husband was used. Paternity Cases Eddie Murphy vs. Scary Spice Mixing of other samples from the lab or crime scene, DNA from the Technician, DNA fragments of the allelic ladder Since only a tiny sample is needed to start amplification, any contaminating DNA that gets into the sample will also be replicated DNA fingerprinting is used to diagnose inherited disorders in both prenatal and newborn babies in hospitals around the world. These disorders may include cystic fibrosis, hemophilia, Huntington's disease, familial Alzheimer's, sickle cell anemia, thalassemia, and many others. Diagnosis of Inherited Disorders Developing Cures for Inherited Disorders Research programs to locate inherited disorders on the chromosomes depend on the information contained in DNA fingerprints. By studying the DNA fingerprints of relatives who have a history of some particular disorder, or by comparing large groups of people with and without the disorder, it is possible to identify DNA patterns associated with the disease in question. This work is a necessary first step in designing an eventual genetic cure for these disorders. Early detection of such disorders enables the medical staff to prepare themselves and the parents for proper treatment of the child. In some programs, genetic counselors use DNA fingerprint information to help prospective parents understand the risk of having an affected child. In other programs, prospective parents use DNA fingerprint information in their decisions concerning affected pregnancies. Detection of Disorders People are using Gene Therapy to intervene 2003 Human Genome Sequenced