paper

The use of deoxyribonucleic acid (DNA) samples in forensic case work has become an increasingly staple piece of evidence. DNA provides unique information about an individual found as short tandem repeats (STRs) located in the nucleus of cells. DNA analysis enables forensic scientists to purify, extract and amplify STRs to generate a genetic profile allowing alleles to be seen that belong to a single person. These STRs are seen as fragments and are amplified or copied numerous times to allow for easier detection. The polymerase chain reaction (PCR) method is used to analyze DNA sequences found in biological fluids. PCR products are seen as peaks representing alleles found at 13 core loci. Ordinary materials have been found to inhibit PCR products such as indigo dye, hematin, humic acid and tannic acid. These substances are fairly common findings at a crime scene and produce unreliable profile analysis. This study proposes an evaluation of DNA extraction and recovery methods after inhibitory factors are presented using blood and saliva test samples. This study will utilize the ethanol precipitation method, clean DNA prep kit and Microcon centrifugal filters to purify inhibited DNA samples. Quality and quantity of the recovered DNA from prepped samples will be compared between the methods of purification. If successful, these methods can be used in forensic casework to obtain reliable results from inhibited evidentiary items.

Introduction

Identification of an individual as the source of a DNA profile in a criminal case using the PCR method has become a reliable tool investigators use. The profiles generated for forensic purposes gives important information about the questions revolving around who’s DNA is found at a ...

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... amount of product from inhibited DNA. The samples will then be amplified using the ABI Prism 7000 and analyzed using the 3130 Genetic Analyzer.

Statistics

The proposed study data set is a repeated measurement of the same thing and can be described as ordinal data which describes categories with importance in order. The purification methods can be ranked from providing the most to least STR DNA data. The relative standard deviation is used for the comparison of analytical methods and is calculated using:

RSD = s / x̄ x 100%

A comparison of the quantitative data may be calculated using the standard error of the difference of the means seen below. ŝ = √ ((n1-1)s12 + (n2-1)s22) / (n1-1) + (n2-1) and SE=ŝ√(1/n1+1/n2)

Quantitative data between purification methods is compared to determine an appropriate and suitable analysis of complex DNA samples with inhibition.