FORS-2106EL Lecture Notes - Lecture 15: Ethylenediaminetetraacetic Acid, White Blood Cell, Hemoglobin
27 Jun 2018
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Forensic Biology - Day 15 2017.11.13.
Lessons From the First Case Involving DNA Testing
-Describes the first use of DNA (in 1986) to solve a double rape-homicide case in
England
-Use of DNA database to screen for perpetrator (DNA only done on 10% with same
blood type as perpetrator)
-Exoneration of an innocent suspect
-DNA was an investigative tool, did not solve the case by itself (confession of
accomplice)
-Local baker, Colin Pitchfork was arrested and his DNA profile matched with the
semen from both murders
-In 1988 he was sentenced to life for the 2 murders
Stages of Forensic DNA Progression
-Exploration (1985-1995) beginnings, deferent methods tried
-Stabilization (1995-2005) Standardization of STR’s, selection of core loci,
implementation of Quality Assurance Standards
-Growth (2005-2009) Rapid growth of DNA database
-Sophistication (the future) expanding tools available, confronting privacy concerns
Historical Methods for DNA Testing
-RFLP: Restriction Fragment Length Polymorphism
-loci: Variable Number of tandem repeats, therefore the same parent of DNA
repeated over and over again
-Multi-locus probes
-Single-locus probes
-PCR-based sequence polymorphisms
-AmpFLPs: Amplified fragment length polymorphism
-Silver Stained Short Tandem Repeats (STRs)
-Fluorescently detected STRs
Blood Group Typing
-Advantages
-Rapid, simple tests
-Only test available for many years
-Limitation
-Poor power of discrimination (about 1 in 10) with such few alleles (ex. inclusions
are not very meaningful)
find more resources at oneclass.com
find more resources at oneclass.com
Forensic Protein Profiling Isoenzyme Characteristics
-Advantages
-Improved power of discrimination over blood group
typing
-Disadvantages
-Poor power of discrimination, even with multiple
systems (1 in 100)
-Poor sensitivity
-Proteins are not always stable in forensic stains or
found in every sample
DNA in the Cell
-We really only look at the small varying region which is different from person to
person
DNA Marker Nomenclature
-D16S539
-D: DNA
-16: chromosome 16
-S: single copy sequence
-539: 539th locus described in chromosome 16
The Principles of RFLP Testing
-Cut the DNA with Restriction enzymes
-Separate Fragments of differing Length by
gel electrophoresis
-Detect length based difference
(Polymorphisms) in DNA fragments of interest
-Need 50 ng DNA, length of fragments range
from 400-12 000 bp (base pairs)
Variable Number of Tandem Repeats
-each repeat is 8-100 bp long
-Only DNA fragments containing a
complementary sequence to the probes are
detected
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lessons from the first case involving dna testing. Describes the rst use of dna (in 1986) to solve a double rape-homicide case in. Use of dna database to screen for perpetrator (dna only done on 10% with same blood type as perpetrator) Dna was an investigative tool, did not solve the case by itself (confession of accomplice) Local baker, colin pitchfork was arrested and his dna pro le matched with the semen from both murders. In 1988 he was sentenced to life for the 2 murders. Stabilization (1995-2005) standardization of str"s, selection of core loci, implementation of quality assurance standards. Growth (2005-2009) rapid growth of dna database. Sophistication (the future) expanding tools available, confronting privacy concerns. Loci: variable number of tandem repeats, therefore the same parent of dna repeated over and over again. Poor power of discrimination (about 1 in 10) with such few alleles (ex. inclusions are not very meaningful) Improved power of discrimination over blood group typing.
