Telomere length analysis: A new tool for molecular photofitting

Abstract

This thesis describes a new assay and analytical protocol to determine the telomere length of an individual, and its potential application in criminal investigations. The most commonly used existing assay is based on real-time qPCR. The Telomeric Multiplication Factor (TMF) assay described here instead uses end-point PCR and densitometry. Because most existing forensic DNA techniques already use end-point PCR, the TMF assay can be more easily integrated into the suite of tests available. Along with the TMF assay, a new procedure to use telomere length to determine age is presented. Previous attempts to do this rely on the calculation of a linear regression, and the interpolation of an age based on telomere length, which is not accurate enough for use in criminal investigations (with a covariance between known and predicted age of 0.2848, P=0.010564). Telomere Length Analysis (TLA) uses a database of known individuals. An unknown individual’s telomere length is compared to all telomere lengths on the database, and used to calculate the unknown individual’s age as a multiple of each age on the database. This increases exponentially the number of comparisons that can be made, and improves the accuracy of age predictions (with a covariance between known and predicted age of 0.4561, P=0.000021). The accuracy increases as the size of the database increases. TLA was developed using buccal epithelial cell samples. However, this thesis demonstrates that TLA also works on hair and blood samples, although to a lesser degree of accuracy. This makes TLA applicable in more forensic scenarios. TLA is intended to operate alongside the recent developments in molecular photofitting, to provide phenotypic and biographical information about an unknown offender to hasten his arrest and conviction, in the event that no matching DNA profile is recorded on investigating authorities’ databases. The new TMF assay and TLA analytical profile are more accurate and more applicable to a forensic scenario than other, previous, attempts to use telomere length to determine age.