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The
Technology |
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DNA
or Deoxyribonucleic acid is present in virtually every cell in our bodies.
It's made up of unique sequences of molecules known as nucleotides. This unique
sequence is what makes blond hair "blond" and brown eyes "brown".
It is also the basis for DNA Testing. |
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DNA tests simply look for unique sequences of nucleotides. This sequence can
be used to determine a relationship between two people. Parents and their children
share similar sequences. |
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DNA
is organized into chromosomes that we inherit from both parents: 23 from our
mothers and 23 from our fathers. Within those chromosomes lie critical clues
in determining paternity, establishing inheritance, examining immigration and
even investigating criminal cases. |
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The
tests can certify the origin of virtually any biological tissue by comparing
it to another known tissue sample of an individual. But because there are so
many nucleotides in one chromosome, finding a unique pattern or combination
or sequence of genetic material can be extremely difficult. That's why
DNA Forensic Consultants uses something
called STRs...state of the art technology. |
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The
Technology as a Solution |
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STR
is an abbreviation for what is know as a "short tandem repeat". This
test looks for short sections of DNA that have unique patterns of nucleotides.
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These
repeated patterns are passed on from parent to child. They are used in determining
paternity/maternity, and can also be used in immigration and inheritance cases. |
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These
repeated STRs are unique to each person and can be used for positive identification
of individuals. These patterns can be extremely helpful in solving crimes. |
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STR (short
tandem repeat) DNA testing has significant advantages over an earlier technology,
called RFLP (Restriction Fragment Length Polymorphism). STR DNA testing can
often be performed on small and/or degraded samples which are often the only
materials available at the crime scene. Such tests may be impossible using
RFLP analysis. Many STR tests can be analyzed at once. Further, the interpretation
is simplified and non-subjective due to the discrete sizes of the STR repeats.
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RFLP
Testing using gels |
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"...STR
DNA testing has become the front-line DNA technology for the forensic community..." |
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Short
Tandem Repeats are repeated units of nucleotides that are usually
2 to 7 nucleotides in length. The forensic community has extensively studied
and collectively decided upon a set of 15 STR tests
which are 5 to 50 exact repeats of the 4 nucleotide (called tetranucleotides).
The number of repeats for each STR system is your genetic signature, and laboratories
around the world can identify it with a great degree of accuracy. |
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How
the technology works... |
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Very small samples, containing minute amounts of DNA (often
degraded), are amplified using the Polymerase Chain Reaction (PCR) procedure.
This procedure is based upon the ability of DNA to be made at very high temperatures
using an enzyme found in nature. In the laboratory, we manipulate the reaction
temperatures for short time intervals and can generate very large amounts of
specific STR units. Fluorescent dye technology increases the number of tests
performed with each PCR run. Currently, 9 STRs and amelogenin (X,Y) can be identified
in one test run. The STRs are sized under electorphoretic conditions and analyzed
using state-of-the-art software. DNA Forensic Consultants, in collaboration
with Clinical Testing & Research, has full state-of-the-art PCR STR capability
with fluorescent dye technology, capillary electrophoresis using the ABI 310
Genetic Analyzer®, GeneScan® data collection and Genotyper® software
for automated
genotyping of alleles.
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The
hot-water pools in Yellowstone National Park were the first sources of an
enzyme that made it possible for DNA to be synthesized at very high temperatures. |
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c.
2001 Martin-Software. All rights reserved |
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