DNA

Running Head : DNA

DNA and Forensic Science

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DNA and Forensic Science

Introduction

Since the advent of criminal investigations , investigators have sought a "gold standard " for the evaluation of forensic evidence . For nearly a century , fingerprints were considered a unique identifier until recent failures in the technology resulted in increased scrutiny from the scientific community (Stacey , 2005 . DNA has usurped the role of fingerprints as the most powerful means of identification currently available . While the foundation of forensic DNA testing technology is firmly

rooted in science , the lack of an objective computational methodology for the interpretation of DNA testing results allows for the introduction of subjectivity

This explores DNA application in forensic science . First background information on DNA is presented . Then , issues related to DNA testing are reviewed . Following , DNA importance to forensic science and police agencies is considered . Finally , some conclusive remarks are presented

Background to DNA

DNA contains the blueprint of the human body (Campbell , 1996 . Almost all human cells contain DNA . Most human DNA is wrapped into 23 pairs of chromosomes within each cell . Half of each chromosome pair is inherited from the individual 's mother and half comes from the individual 's father . Chromosomes each contain many functional components called genes . When it is possible to distinguish between two or more variants of a single gene , those variants are called alleles . At the finest level of scale , chromosomes and genes can be described as a sequence of nucleotides (named for the nitrogenous bases they contain . Nucleotides are present in four forms : adenine (A , guanine (G , cytosine (C , and thymine (T . In its typically double stranded form , an "A " on one DNA strand always pairs with the "T " on another , and a "C " will always pair with a "G . This association is called a "base pair (Dennis et al 2002 . At this level , the familiar double helix can be visualized (see Figure 1

Figure 2 .1 : DNA being unraveled from the nucleus of a cell (The National Health Museum , 2008

The sugar-phosphate backbone creates the familiar double helix and is made up of linkages between the phosphate of one nucleotide and the sugar of the adjoining nucleotide . The interior of the double helix is made up of pairs of nitrogenous bases , held together by hydrogen bonds The pairing of bases is specific : adenine (A ) can only pair with thymine (T ) and cytocine (C ) can only pair with guanine (G . DNA is grouped into 23 pairs of separate chromosomes and resides in the nucleus of all nucleated cells (Campbell , 1996

The human genome contains approximately 3 .12 billion base pairs and is virtually identical between all humans (Dennis et al , 2002 . A distinction is often made between meaningful DNA (e .g . genes or the regions containing the coding information for proteins and other gene products ) and non-coding , or "junk " DNA that holds no known function Even distantly related humans are approximately 99 .5 identical at this level of their DNA (Dennis et al , 2002...