| Success Rates for DNA Extraction from
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| | street and exposed to the elements (e.g.
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| Non-Standard Samples
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| | rain).
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| In part 1 of the article, we looked at
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| | Low (20% - 30%) For samples such as teeth
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| some of the more common non-standard
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| | or bone, where extracting DNA is a
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| samples used to obtain DNA from an
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| | relatively difficult and time consuming
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| individual for DNA testing purposes. In
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| | process, these normally need to be
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| this article we look at DNA extraction
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| | handled by a highly specialised
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| success rates from the various types of
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| | laboratory. In such cases, the individual
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| samples and how these can vary from one
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| | should consult the laboratory first to
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| sample to another.
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| | check their level of expertise, if they
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| Non standard samples do not always
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| | will accept the sample and the cost.
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| guarantee that a DNA Profile will be
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| | The classification above is however only
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| obtained. Whilst for buccal swabs it is
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| | a guideline, since as we have seen it is
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| possible not to obtain DNA, such as in
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| | not just the type of sample that is
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| cases where the swabbing was not
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| | important but also other variables can
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| adequately performed or else the swabs
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| | have an influence such as :
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| grows mould due to damp storage
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| | 1. Poor storage conditions (e.g. damp
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| conditions, in general problems with this
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| | environment, extreme heat etc)
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| type of sample are normally less than 2%.
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| | 2. Poor sample handling (possible
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| Therefore depending on the nature of the
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| | contamination with other DNA or dirt by
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| sample, there is usually associated a
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| | touching the sample)
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| High, Medium or Low probability of
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| | 3. Not enough DNA present (e.g. heavily
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| success in extracting DNA from each type
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| | used toothbrush vs used once only)
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| of sample (in some cases a percentage
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| | It is also important to note that the
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| probability of success is provided).
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| | success rate will also depend heavily on
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| High (80%) : For samples such as fresh
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| | the ability of the laboratory performing
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| blood stains or hairs with root where,
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| | the test. Not all laboratories that can
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| for a qualified and experienced DNA
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| | perform DNA Paternity testing on normal
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| laboratory, extracting DNA is considered
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| | swabs are capable of obtaining DNA from a
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| relatively straightforward. In such
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| | wide variety of other media. The more
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| cases, as long as the sample is handled
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| | difficult the media (e.g. teeth and
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| properly both during collection and
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| | bone), the greater the specialisation and
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| delivery to the laboratory, one can
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| | experience required to increase the
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| expect a high probability of success in
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| | chance of a successful DNA extraction.
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| extracting DNA.
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| | Finally, it is also important to note
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| Medium (50%-60%) : For samples such as a
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| | that with non-standard samples there is
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| toothbrush or cigarette butts the success
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| | always a risk that the extraction will
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| rate is influenced by a number of
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| | not work. Therefore any person
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| variables including heavy use vs light
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| | considering submitting such a sample,
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| use and/or storage conditions etc.
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| | especially where it may be only a limited
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| Therefore a heavily smoked cigarette butt
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| | sample available (e.g. person is dead),
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| found in an ashtray at home is more
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| | should take this into consideration.
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| likely to result in a successful DNA
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| | Selection of an experienced laboratory
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| extraction than a lightly smoked
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| | (possibly of forensic specialization)
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| cigarette that has been thrown on the
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| | will help minimize this risk.
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