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In the last decade a range of DNA-based analytical procedures have been developed for meat speciation purposes. Even highly processed foods contain small quantities of residual DNA that can be amplified by the Polymerase Chain Reaction (PCR). A variety of PCR tests can discriminate between different meat and fish species or between plant species found in juices and honeys or detect the presence of genetically modified cereals. However, for the use of PCR-based tests for routine food analysis there is usually an additional requirement for quantitative testing, in order to check that 'adulterants' are not present - either by accident or deliberate malpractice.
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Although real-time PCR is a system that is emerging for use in quantitative PCR work, it can be expensive and requires specialist equipment. This project aims to investigate the possibility of developing a simpler yet accurate quantitative technique for the purpose of food authentication using competitive PCR coupled with fluorescent molecular probes (beacons).
The project will concentrate on developing a model system in the form of quantitative tests to detect chicken DNA in the presence of DNA from other meat species.
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A fragment from the alpha-cardiac actin gene will be used as the target sequence to produce a chicken specific PCR. To account for the sheared DNA expected to be present in processed food products a small fragment of around 100bp will be used.
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An artificial 'competitor' sequence will be created by introducing a short additional 'randomised' sequence into the middle of chicken target sequence leaving the PCR primer sites unchanged. This will act as 'internal standard DNA'.
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The competitive PCR procedure will be assessed to determine if it is functioning correctly. Consequently, probes will be designed for detection of the target and competitor PCR products. The technique will be tested to confirm that the dual florescence signals give the same estimate of target DNA as the conventional method.
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The procedure will then be applied to DNA from ground meat mixtures.
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Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food Standards Agency Research webpage</a>.