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Considerations for Exposure to Diazinon and Chlorpyrifos - page 15 / 49





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DNA Analysis of the PON1-192 Polymorphism

A DNA segment that includes the polymorphic site that specified which amino acid appears at position 192 is amplified by enzymes in a process referred to as a polymerase chain reaction (PCR).  A method that has come to public attention through highly visible criminal trials.  The resulting fragments of DNA are exposed to a specific restriction enzyme that will cut DNA containing the codon for Q, but not for R.   The fragments are separated by an electrophoretic procedure, then stained and photographed.

In the next slide, the uncut polymerase chain reaction (PCR) product runs at the position of the upper arrow, while the cut sequence runs at the position of the lower arrow.  The genotypes of the individuals are shown above their respective band patterns.  X = no DNA in the amplification reaction.  Q = DNA from a Q/Q homozygote, R from an R/R homozygote. The PON1-R192 allele was shown to be the high paraoxonase activity allele and the PON1-Q192 allele the low metabolizer allele.  As noted below, we recommend not using this  protocol, but instead, a functional analysis that provides additional information on PON1 levels which are as important or more important than the amino acid present at position 192.

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