Deoxyribonucleic acid (DNA) contains the genetic material of almost every organism. It is also unique and permanent, turning it into a suitable form of evidence in crimes such as serial murders. But the usage of forensic DNA evidence in the investigation of serial murders is not without controversy. Critics often point out that the usage of forensic DNA evidence often results in issues such as the invasion of privacy and the mishandling of evidence. DNA in Serial Murders The discovery of deoxyribonucleic acid (DNA) is one of the greatest milestones in the history of science.
DNA is said to be “the most central substance in the workings of all life in Earth” (Calladine, Drew, Luisi and Travers, 2004). It contains the genetic material of almost every organism, as well as the information needed to enable processes such as cell division. Virtually every cell in a person’s body possesses similar DNA (MSN Encarta, 2008). Two notable qualities of DNA are its uniqueness and permanence. No two individuals – not even maternal twins – share the exact same DNA. Neither does DNA change – an individual carries the same DNA from birth until death.
Thus, it is no longer surprising is DNA analysis became an important procedure in forensic science. DNA derived from even just a single strand of hair can solve a murder that occurred more than 20 years ago. DNA: Structure, Functions and History DNA is found mainly in the nucleus of a cell. The nucleus is regarded as the “control center” of a cell, as it contains the genetically-coded instructions for cellular activities like growth and reproduction. These directions are found in the chromosomes, the chemical units that constitute DNA (Silverstein and Nunn, 2002).
Indeed, without DNA, the cell will not be able to live up to its definition as the most basic unit of an organism. Structure A single DNA molecule is actually a long, threadlike chain of chemical units called nucleotides. Each nucleotide, in turn, is composed of a phosphate, a nitrogen base and a sugar called deoxyribose (Silverstein and Nunn, 2002). A nucleotide’s nitrogen base can be one of the following: adenine (A), guanine (G), thymine (T) and cytosine (C) (MSN Encarta, 2008).
The sugar phosphates serve as the backbone of the chain – they start the formation of the chain by linking themselves together. In the process of this connection, the nitrogen bases stick out and can react with other bases on a different chain (Silverstein and Nunn, 2002). Functions DNA contains the necessary information that enables two important operations – protein synthesis and replication. Protein synthesis refers to the generation of proteins that the cell needs for its development and activities (MSN Encarta, 2008).
The four-letter alphabet of DNA’s nitrogen bases form codons that are copied into ribonucleic acid (RNA). RNA, consecutively, is translated into amino acids – the building blocks of protein. There are 23 different kinds of amino acids (Silverstein and Nunn, 2002). Amino acids create specific groupings that produce various types of proteins. Proteins are “(the expressions of) DNA’s instructions that determine the traits of each organism” (Silverstein and Nunn, 2002). They either form body structures or direct chemical reactions inside a cell.
One example of an amino acid combination is keratin, a protein that is a major component of hair and fingernails (Silverstein and Nunn, 2002). DNA undergoes replication when it copies itself shortly before cell division – the information that is required for protein synthesis is also passed on in the process. The two polynucleotide chains of a DNA molecule separate, resulting in the release of nucleotides. Each of these nucleotides, in turn, attracts a matching nucleotide that the cell had formed earlier. The rungs of a new DNA molecule is then formed as hydrogen bonds fuse the nucleotides to one another.
An enzyme called DNA polymerase fit the complementary nucleotides into place by connecting the phosphate group of one nucleotide to the sugar molecule of the adjacent nucleotide (MSN Encarta, 2008). History Austrian monk Gregor Mendel (1822-1884) is believed to be the pioneer of DNA research. Even before the discovery of nucleic acid, he has already established the laws of inheritance through the selective breeding of peaplants. In 1865, he argued that plants inherited certain characteristics from their parents as a result of certain “factors.
” Nucleic acid was finally discovered in 1868 by the Swiss biochemist Friedrich Miescher (1844-1895). He managed to do so by studying nuclei that was derived from pus cells taken from surgical dressings (Science. JRank. org, 2008). By the mid-20th century, several studies have already been conducted regarding nucleotides and their role in the formation of DNA. However, it was still not established as to whether or not DNA was indeed the molecules of heredity – the prevailing belief during this period was that proteins were the genetic material of almost every organism.
Oswald Avery (1877-1955) and his colleagues debunked this idea in 1944 through their studies of pneumococcus, the bacterium that causes pneumonia. Their experiments revealed that “non-pathogenic strains of (the bacteria became) pathogenic (when treated) with a DNA-containing extract from heat-killed pathogenic strains” (Science. JRank. org, 2008). Avery therefore concluded that DNA, not protein, was the genetic material – a claim whose validity was affirmed by other studies in 1952 (Science. JRank. org, 2008). James Watson (1928 –) and Francis Crick (1916 –) created the double-helix model of DNA in 1953.
This representation was based on their correct deduction that the sequence of nucleotides contained the genetic information about an organism. Their discovery resulted in the field of molecular genetics. Eight years later, scientists discovered the trinucleotide sequences that formed 20 of the 23 amino acids (Science. JRank. org, 2008). The 1970s was the advent of genetic engineering and biotechnology. It was during this decade that scientists were able to come up with DNA molecules that were composed of segments from different organisms.
The development of DNA fingerprinting in 1984 resulted in the inclusion of DNA typing in forensic science – a technique which first led to a conviction in 1987. In 1990, gene therapy (the manipulation of DNA to correct deficiencies) and the Human Genome Project (which aimed to determine the nucleotide sequence in the DNA of the entire human genome) were discovered. These were later followed by more advanced DNA-related technologies such as animal cloning (Science. Jrank. org, 2008).