Criminology Research Council grant ; (3/87)
The aim of this research was to establish and evaluate methods suited to the analysis of forensic type samples so as to provide reliable scientific evidence in legal proceedings.
The research findings resulting from this project are a short report and a collection of articles which have been published in various journals.
This project established a new method of genetic 'fingerprinting' of human (and higher primate) DNA. The results show there to be a complex restriction fragment length polymorphism associated with Satellite III DNA sequences in the human genome. This gives a multibanded profile of the DNA in question. The primary probe sequence that was developed to demonstrate this polymorphism is coded 228S.
This Satellite III 'macrosatellite' polymorphism represents an alternative method to those based upon 'minisatellite' hypervariation for either the discrimination of individual genomes in criminal forensic studies or in establishing parentage. Conservatively estimated, the average chance of two individuals having the same DNA fingerprint with probe 228S is one in 100,000 people.
The probe 228S (patented and marketed by Bresatec limited as Polysat 3TM) has its principal practical advantage in the use of the same probe for either sexing human genomes (HaeIII digests) or for discriminating between individuals (TaqI digests). The probe is known to hybridise only to higher primate DNA and thus may be used for quantifying human DNA in mixtures of human and non-human, for example, microbial DNA. Results may be achieved using non-isotopic probe methods, using photobiotinylated probes.
The principal practical disadvantages are the complexity of the polymorphic pattern, its interpretation and comparison. The size range of the Satellite III/TaqI fragments require the source DNA to have a high initial integrity, whereas both the quantity and quality of DNA recoverable from typical forensic specimens may often be limiting. There is also no potential for in-vitro amplification of the Satellite III polymorphism as is now possible with some single locus 'micro' satellite sequences (by the polymerase chain reaction).