The expert system of genotype discrimination for D5S818 locus based on near-infrared spectroscopy-principal discriminant variate.

ABSTRACT

This paper studied the expert system of genotype discrimination for the STR locus D5S818 based on near-infrared spectroscopy-principal discriminant variate (PDV). Six genotypes, i.e. genotypes 10-10, 10-11, 11-11, 11-12, 11-13 and 13-13, were selected as research subjects. Based on the optimum polymerase chain reaction (PCR) conditions, about 54 measuring samples for each genotype were obtained; these samples were tested by near-infrared spectroscopy directly. With differences between homozygote genotypes and heterozygote ones, and differences of the total number of core repeat units between the six genotypes, two types of genotyping-tree structure were constructed and their respective PDV models were studied using the near-infrared spectra of the samples as recognition variables. Finally, based on the classification ability of these two genotyping-tree structures, an optimum expert system of genotype discrimination was built using the PDV models. The result demonstrated that the built expert system had good discriminability and robustness; without any preprocessing for PCR products, the six genotypes studied could be discriminated rapidly and correctly. It provided a methodological support for establishing an expert system of genotype discrimination for all genotypes of locus D5S818 and other STR loci.