Table 3 Sequences of the probes used for real-time PCR of CYP1A2
Detected allele Sequence of probe 5'-3' Reference
*1F GGGCCCAGGACGCAT-Flu 
Phenotyping using caffeine showed no difference in CYP1A2*1F metabolic activity between different genotypes in nonsmokers but a significant difference in smokers homozygous for the A allele compared with the other genotypes in terms of a 1.6-fold increased activity.1-17-1 Unexpectedly, another study demonstrated a lower in vivo activity in patients with colorectal cancer than in healthy controls.
The frequency of the *1F allele seems to be higher in Caucasians compared with Japanese. The study which investigated this new polymorphism analyzed 159 healthy Japanese and detected a prevalence of 39% homozygous and 44.6% heterozygous subjects. In contrast, another study examined 236 Caucasians and found 46% homozy-gous A/A alleles and 44% heterozygous A/C alleles.
In routine genotyping of CYP1A2, only *1F and a second allele, *1D, the deletion of T at position — 2464, need to be analyzed because all other CYP1A2 polymorphisms are in linkage disequilibrium with these two alleles.
At present, only one study has described real-time PCR methodology for the detection of CYP1A2*1F. This was performed employing the LightCycler™ instrument and fluorescent hybridization probes and melting curve analysis. (For detailed information of the probes, see Table 3.)
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