GENETIC FINGERPRINTING

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GENETIC FINGERPRINTING

• A look at a
• powerful
• forensic
• investigative
• tool!

Casey Stroz SBF-03
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Introduction

• Genetic fingerprinting is largely the result of
  DNA analysis using a variety of techniques. It
  has come into great prevalence in the 21th
  Century as convictive evidence in criminal trials
  and crime scene investigations.
• It is one of, if not the most, commonly used
  methods of practice in all of Forensic Science
  and Criminology.

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DNA

• Deoxyribonucleic acid is a nucleic acid in the
  body that contains instructions for functionality
  and development in organisms. It is effectively
  called the blueprints of an organisms body and
  contains vital information about cell
  construction and structure.
• The DNA double helix is held together by base
  pairs of hydrogen bonded nucleotides.
• DNA is organized into Chromosomes and determine
  gender as a result of cellular division and DNA
  replication.

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RNA

• Ribonucleic acid is a nucleic acid that is single
  stranded as opposed to the double strands of DNA.
• RNA largely processes enzymes and is key to
  processing proteins and carry information to
  ribosomes around the body.
• Messenger RNA is usually the type of RNA
  information carrier, and are one of many that
  regulate and cycle in active genes.

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Building Blocks of Base Pairs

• DNA and RNA have their nucleotides connected by
  hydrogen bonds.
• Base pairs are, as the name implies, comprised of
  two bases paired together by hydrogen bonds.

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AGCT and sometimes U

• The bases are paired together in a helix or
  double helix and are identified using the AGCT/U
  acronym.
• The acronym stands for adenine, guanine,
  cytosine, thymine (DNA), and uracil (RNA).

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ADENINE

• Adenine is a base in the strands of DNA and RNA.
  Using hydrogen bonds, it attaches to Thymine and
  Uracil, respectively.
• Adenine also finds use in cellular metabolism
  when it forms organic compounds with phosphate.

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GUANINE

• Guanine is a base in the DNA and RNA strands.
  Using hydrogen bonds, it attaches to Cytosine.
• Guanine crystals serve as an additive to cosmetic
  products because they produce an iridescent
  effect, adding sheen and luster.

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CYTOSINE

• Cytosine is another base in both DNA and RNA
  strands. It hydrogen bonds with Guanine.
• Under certain circumstances, it can also point
  mutate into uracil and cause damage to a DNA
  strand.

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THYMINE

• Thymine is the fourth base in the nucleic acid of
  DNA.
• It is found exclusively in DNA, and attaches to
  Adenine through hydrogen bonds.
• It is also a common target in cancer treatment
  and is attacked in order to prevent excess
  cellular growth.

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URACIL

• Uracil is the fourth base in the nucleic acid of
  RNA.
• It is found exclusively in RNA, and attaches to
  Adenine through hydrogen bonds.
• It has successfully been scientifically
  synthesized, so that it is similar to the uracil
  that naturally occurs in both plants and animals.

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Alleles and Lengths

• Alleles are pairs of series in a gene and are
  used in coding sequences. It determines genotypes
  within a gene. They generate genetic variation
  within a species and explain differing
  characteristics between organisms.
• Dominant and recessive genes are largely the
  result of wild type alleles and mutated alleles,
  and in humans, can determine such things as body
  types, hair color, and eye color. There are
  genetic disorders based on these gene types, such
  as albinism, cystic fibrosis, Tay-Sachs Disease,
  and Huntingtons Disease.
• VNTR analysis shows variation between alleles in
  several individuals.

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Techniques for Analysis

• There are several major techniques for analyzing
  genetic fingerprints.
• These include RFLP, PCR, STR, AmpFLP,
  Y-Chromosome, and Mitochondrial analysis.

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RFLP Analysis

• Restriction fragment length polymorphism analysis
  is an early DNA analysis technique done by using
  Southern blotting applied to restriction enzyme
  digestion.
• A main flaw with this technique is that it calls
  for a large amount of undegraded sample DNA to
  show any results.
• Using this technique makes it difficult to
  observe individual alleles.

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PCR Analysis

• Polymerase chain reaction analysis allows for
  degraded or smaller DNA samples to be amplified
  in specific areas. It also makes DNA analysis
  easier and faster than ever before.
• A flaw with this system lies in the difficulty of
  determining DNA profiles amongst mixed DNA
  samples. As compared to RFLP analysis, it was
  slightly more difficult to find differences
  between samples.
• Using PCR analysis is useful largely for the fact
  that it can analyze VNTR loci and easily be
  incorporated into a database system.

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STR Analysis

• The most commonly practiced technique of DNA
  analysis is a subset of PCR analysis that makes
  use of short tandem repeats. This technique, like
  PCR, focuses on one area of a DNA sample and
  analyzes 4 repeated base pairs. This is key in
  discerning the DNA of different individuals as
  well as identifying them. The fragmented DNA
  derived from this technique are separated via
  electrophoresis.
• STR Analysis is the basis and template by which
  DNA Databases are organized internationally. It
  also discriminates to the highest degree of any
  other DNA analysis technique.

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AmpFLP Analysis

• Amplified fragment length polymorphism is an
  advanced form of PCR analysis that can be
  automated and cheaply done.
• A flaw with this technique comes with its
  efficiency. The gel techniques used to analyze
  the DNA may cause grievous errors in analysis,
  such as common allelic dropout.

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Y-STR Analysis

• The Y-Chromosome is found only in males, and
  therefore can help determine paternal family
  lines and male profiles.
• Y-STR Analysis can and may be used when
  differential extraction is not readily available
  or possible.

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mitDNA Analysis

• Mitochondrial DNA analysis is most commonly used
  when it is impossible to get one of the thirteen
  STR DNA profiles. And is used as an alternative
  following a failed STR profiling.
• This technique, similar to Y-Chromosome Analysis,
  allows for maternal family lines to be traced
  directly and the identification of female
  profiles.
• It is commonly obtained through bone matter and
  hair proteins, as well as other tissue samples.

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Databases

• National DNA Databases are set up internationally
  and are organized by country.
• The first to be set up was the United Kingdom
  National DNA Database in 1995.
• Databases are also broken down by region and
  state. In the United States, each of the 50
  states has its own DNA database.
• Whether repeat criminal offenders or normal
  civilians are entered in a database is left to
  government regulation.

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Testimonial Value

• DNA evidence must be presented by the expert who
  compared them and the evidence itself must
  physically be present in the courtroom. It must
  be presented with complete evidence history as
  well as sources of the matching profiles.
• The Judge must also instruct the jury on the
  significance of a genetic match, as well as
  likelihood ratios and all information that
  relates directly to the case.
• The Jury should thus reflect on the evidence
  based on common sense to provide an accurate
  assessment and judgment of the person on trial.

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Historically Notable Cases

• Anna Anderson claimed she was the lost Grand
  Duchess Anastasia Nikolaevna of Russia, though
  when her tissue samples underwent DNA fingerprint
  analysis, the results of connection came up
  negative. This case involved mtDNA analysis.

• The famous O.J. Simpson Trial showed how
  handling mishaps of evidence can completely turn
  the conviction of a crime the other way. The
  prosecutors relied heavily on DNA evidence in
  their attempt to convict him of a double homicide.

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More Historic Cases

• Dr. Richard Schmidt was connected to a second
  degree murder when a connection was also made
  between viral DNA, HIV, and AIDS. He injected his
  girlfriend with HIV, killing her.
• Tommie Lee Andrews was the first rapist convicted
  largely as a result of DNA evidence swabbed from
  his victim.
• The South Side Strangler, Timothy Spencer, was
  the first man in the US to be sentenced to death
  as a result of the connection between him and
  several related crimes via DNA analysis.

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Still More Historic Cases

• The hair of a cat named Snowball was used to
  connect a man to the murder of his wife in 1994.
  This was the first instance of animal DNA being
  used to convict and identify a criminal.
• An innocent relative of a criminal matched by DNA
  was a key component in the murder conviction of
  Jeffrey Gafoor. This occurred through a DNA match
  with his civilian nephew.
• In the trial of Robert Pickton, DNA was used to
  identify the victims of the case, instead of the
  defendants conviction.
• Evan Simmons, after 24 years in jail, was proven
  innocent of a crime he was convicted of
  committing in 1981 based on post-conviction DNA
  Testing.

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Informative Sources

• http//www.ncbi.nlm.nih.gov/projects/genome/probe/
  doc/TechRFLP.shtml
• http//www.sumanasinc.com/webcontent/animations/co
  ntent/pcr.html
• http//www.cstl.nist.gov/biotech/strbase/index.htm
  
• http//www.keygene.com/keygene/techs-apps/index.ph
  p
• http//www.bradshawfoundation.com/stephenoppenheim
  er/
• http//www.wikicrimeline.co.uk/index.php?titleDNA
  _profilingPresentation_and_evaluation_of_evidence
  _of_partial_or_incomplete_DNA_profiles