Note: Descriptions are shown in the official language in which they were submitted.
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PROPOSAL FOR PATENT FOR INTERNAL IDENTIFICATION MARKERS- R.M. JOBIN
Introduction
Almost every type of scientific endeavour involves analysis of some type of
sample. Usually these samples
are collected over some period of time and/or from different sources and then
processed for analysis at the same
time. This is done in order to be expedient, but unfortunately exposes the
scientist to some risks. Because the
samples are processed together, there is a chance that they could be switched
or that samples could cross
contaminate each other leading to erroneous results. In samples used in
forensic or diagnostic analysis, these
types of errors can lead police officers or physicians to make incorrect
conclusions with disastrous results. The
problem in both cases is that the outcome of these results is of the utmost
importance. A mistake can be
extremely costly to the client and/or the agency doing the analysis. For
example, if several suspects have their
DNA analysed to see if it matches that found at a crime scene and the samples
belonging to two individuals are
switched during analysis the wrong person may be incarcerated and eventually
executed. Similarly, if a sample
containing the victim's profile contaminates a sample containing the suspects
profile it may result in a wrongful
conviction. In diagnostic analysis, misdiagnosis of serious conditions may
result in the loss of a patient s life.
Conversely, false positive results may cause a patient to experience
unnecessary anxiety. To combat this type
of problem I have devised a method of marking individual samples so that if
they are switched for other
samples, or are contaminated with other samples, it will be immediately
apparent.
The Idea
The idea for patent includes the selective and controlled "spiking" of test
samples with known markers which
do not interfere with the test being conducted. The retention of the order of
these markers as originally
introduced serves to demonstrate and validate the use of correct sample
handling. The marker can be a single
type of molecule at a single concentration or any number of molecules at any
number of concentrations. One
can readily see that a number of molecules added to a sample at varying
concentrations can potentially act as a
serial number for that individual sample. However, formulating a unique marker
for each sample is not
necessary for most cases of sample analysis. In most cases it is possible to
reuse the same markers) in a
repeated pattern. This pattern could be: the use or exclusion of a single
marker in an alternating fashion, the
alternation of two different markers or any pattern of any number of markers.
In addition to verifying that the
samples have retained their proper order during analysis, these markers can
also serve as an indicator of the
occurrence of cross contamination. If some of the markers) from adjacent or
even other samples appear in a
sample that is not supposed to contain it (or them), it indicates that cross
contamination has occurred. Because
these markers serve to identify individual samples and are in fact actually
part of the sample, I refer to them as
Internal Identification Markers (IIM). It should be iterated that these
markers should be selected in such a
fashion that they can in no way interfere with the test that is being
performed and in no way obscure the final
results.
Some Examples
To further clarify the use of the IIMs I will give an example of how they
might be deployed. If two IIMs (A
& B) are being used, sample one could contain IIM (A), sample two could
contain (B) while sample three
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Some Examples
To further clarify the use of the IIMs I will give an example of how they
might be deployed. If
two IIMs (A & B) are being used, sample one could contain IIM (A), sample two
could contain (B)
while sample three would contain neither A or B. This pattern (or order) can
be repeated throughout
the rest of the samples. The addition of the IIMs gives the scientist a known
result to look for in
each sample. If this result is altered or not present the researcher knows
that something has gone
wrong. For example if an IIM appears in sample 3, 6, 9...etc. it indicates
that a sample switch or
cross contamination has occurred.
As a real example of how IIMs can be used, I will describe a system of markers
that could be
used in DNA analysis using Polymerase Chain Reaction (PCR) amplification of
Short Tandem
Repeats (STRs) for forensic identification. This process uses small pieces of
DNA called primers
that attach to specific regions of human DNA to direct enzymatic copying of
these regions in an
exponential fashion. Within hours, billions of copies of these short
repetitive DNA segments are
made. The length of these particular segments varies within human populations.
Therefore by
measuring a number of such areas it is possible to identify individuals.
Using bacterial DNA, the scientist can engineer a segment of DNA of a specific
size that falls
well outside of any of the sizes of DNA that is used for human identification
and that is not found in
any naturally occurring bacteria. Then primers can be made that are specific
for this bacterial DNA.
This bacterial marker DNA and its primers can be mass produced and used as an
IIM. A small
amount of marker DNA could be added to every other sample before the DNA is
extracted.
Because the DNA is not human it will not interfere with the Human DNA probe
that is used for
quantification of DNA or the human DNA primers that are also specific for
human DNA. After the
samples have been amplified and run on a gel, the scientist would look for a
repetitious appearance
of the amplified IIM product in alternating lanes. The absence of this pattern
would immediately
indicate that a sample had been switched or there had been a cross
contamination of samples.
Because of its unique size, the amplified marker could not be mistaken for or
interfere with the
analysis of a human profile. It would also serve as an amplification control.
Which means that
when the marker amplifies it also serves to assure the components of the
system are functioning
properly. Use of this system would give the Forensic Scientist assurance that
during analysis no
samples were switched or contaminated. Furthermore, it would negate the
necessity of repeating
samples or doing them in duplicate. The result is an increase in efficiency
with greater confidence
in the results.
In the analysis of medical diagnostic samples a similar system can be
utilized. If PCR is used to
detect genes for various cancers or presence of specific bacteria, a marker
that is based on an
engineered segment of DNA would be extremely useful. Just as in the above
mentioned case for
forensic science, the markers would indicate the occurrence of sample
switching and cross
contamination of samples. In the case of medical diagnostic tests the aim of
the system is to
prevent the misdiagnosis of patients and protect the medical system from legal
action.
Although both of the examples given dealt with the analysis of DNA, similar
markers can be
constructed for any type of analysis including: RNA, proteins, or any organic
or inorganic
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compound. Specially engineered molecules can be designed (if appropriate ones
don t already exist)
that will not interfere with the analysis but can still be detected by the
analytical technique.
Conclusion
IMMs represent an inexpensive, simple and effective way to validate proper
handling of
important samples in any laboratory setting. By enabling labs to easily
identify errors this system
will greatly reduces costs incurred by litigation and damage of reputation
that occur when mistakes
happen. Further more by indicating exactly where the mistakes have taken place
IIMs can act as a
trouble shooting tool enabling a laboratory to quickly diagnose and correct
their sample handling
problems.
