Kasai, Kentaro

JAPANESE
FORENSIC SCIENTIST

Kentaro Kasai is a forensic scientist working in Japan who, in 1990, published the first scholarly paper proposing the use of the D1S80 locus (specific location on a chromosome ) for forensic DNA analysis.

Every human somatic cell nucleus contains approximately 6.4 billion base pairs of DNA. Portions of that DNA encode more than 100,000 genes, the remainder of the DNA is non-coding. In the universe of humans, virtually 99.9% of all DNA is identical among all people, however, the remaining 0.1% makes critical distinctions, and allows for individual DNA typing. The scientific analysis of DNA, and the forensic science of DNA profiling , focuses on the highly variable regions of DNA. One form of that DNA variability is referred to as variable number of tandem repeats (VNTR).

Kentaro Kasai chose to focus his DNA analysis research on a variable number of tandem repeats locus labeled D1S80. D1S80 is located on human chromosome 1. It is composed of repeating units of 16 nucleotide long segments of DNA. The number of repeats can range from 15 to more than 40, depending upon the individual.

The D1S80 locus has been subjected to a variety of scientific tests in order to determine its specificity, reliability, and validity for use as a genetic identifying marker in criminal investigation and forensic science identification . Ethnically different samples have been used for validation (Native American, African American, and European American or Caucasian), using tissue and serology samples similar to those used in forensic settings: vaginal secretions, saliva, semen, blood , and hair, in order to ascertain whether there was uniformity of results across sample types within an individual. When the specimens were typed, there were found to be consistent and reliable results within each individual. The samples were each run twice, and also were sent to different (independent) labs for analysis. All typing results, from both laboratories, for each individual, were exactly the same. This is indicative of extreme reliability and validity of the D1S80 locus as a forensic science marker for individual identification.

The D1S80 locus was also tested for reliability through the use of restriction fragment length polymorphisms (RFLP ) used as markers on genetic linkage maps, and through the use of polymerase chain reaction-(PCR-) based tests. In every analysis, the D1S80 locus has been proven to be a highly sensitive, reliable, and accurate marker for individual genetic (DNA) identification.

Through his pioneering the use of the D1S80 locus in DNA analysis, Kentaro Kasai has made an important and lasting contribution to the world of forensic science.

see also DNA; DNA fingerprint; Mitochondrial DNA typing.