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Hidden truth: Double helix of evidence
Samer Yammine
Legal science started in the 8th century when the Chinese used fingerprints to verify the identity
of significant documents. Afterward, a new field entitled Forensic Science was formed by
merging Mathematics, Chemistry, Physics and Biology, toward the designing of novel techniques
that will assist in cracking crimes.
Sherlock Homes said: ‘’it has long been an axiom of mine that the little things are infinitely the
most important’’, however no one visualized that this little thing, the DNA molecule, would
develop into the most powerful tool against crime. Supported by the theory of transfer: ‘’When
two objects meet, some evidence of that meeting can later be found and verified’’, the idea arose
the idea of collecting and analysing evidence located at crime scenes, in particular biological
samples. The difficulties that most scientists encounter in identifying a biological sample, or
tracking it back to the tissue where it originates from made the development of new techniques a
necessity.
Methylated spots that consist of methyl group on a cytosine nucleotide found in human
genes and their variations among different tissues can be exploited with the creation of novel
techniques to identify particular biological samples from specific tissues. All human cells contain
DNA inherited from both parents, called nuclear DNA. Outside the nucleus, but still within our
cells, a small organelle named the mitochondrion is located. This organelle, responsible for the
production of energy, contains a circular DNA molecule known as mitochondrial DNA.
Mitochondrial DNA is inherited strictly along the maternal line. Thus, it is employed in forensic
science for analysis of populations and family lineages. Mitochondrial DNA substitutes nuclear
DNA analysis whenever collected evidence contain deteriorated or degraded DNA.
In my study, I attempted to design a sensitive and specific assay for both quantitative and
qualitative profiling of gene including specific methylated spots in various tissues. This assay
will help in the identification of unknown biological samples. Data from methylated positions
were too difficult to be analyzed and compared between different samples. Understanding more
the methylation process and choosing new genes would present robust results by this assay. I
also assembled a mitochondrial DNA population database for the Swedish population. This
database will play an essential role during investigation when DNA recovered from evidence can
be matched to suspects. Sequences achieved during my work were stored for future uploading
into the European populations’ database.
Degree project in biology spring 2007
Examensarbete i biologi, 20 p
Biology Education Centre and Department of Genetics and Pathology
Rudbeck, Uppsala University
Supervisor: Marie Allen