Dna Forensics And The Human Genome - 2746 Words

DNA Forensics Before the 1980s, courts relied on testimony and eyewitness accounts as a main source of evidence. Notoriously unreliable, these techniques have since faded away to the stunning reliability of DNA forensics. In 1984, British geneticist Alec Jeffreys of the University of Leicester discovered an interesting new marker in the human genome. Most DNA information is the same in every human, but the junk code between genes is unique to every person. Junk DNA used for investigative purposes can be found in blood, saliva, perspiration, sexual fluid, skin tissue, bone marrow, dental pulp, and hair follicles (Phillips, 2008). By analyzing this junk code, Jeffreys found certain sequences of 10 to 100 base pairs repeated multiple†¦show more content†¦Except in the case of identical twins, the probability that two people have the same genetic code at all thirteen core loci is less than one in one trillion (Crest, 2005). Investigators compare these genetic fingerprints with p rofiles stored in databases of previous offenders, and if they find a match, it proves that the person was at the crime scene. DNA forensics can also narrow down suspect pools, exonerate innocent suspects, and link crimes together if the same DNA is found at both scenes. However, without existing suspects, a DNA profile cannot direct an investigation because current knowledge of genotype-phenotype relation is too vague for DNA phenotyping. For example, a profile from a first time offender that has no match in any database may give the information that the criminal is a left handed male of medium stature with red hair and freckles. It would be impossible to interview every man who fits that description. However, with available suspects, DNA forensics has many advantages over other forms of evidence. One is the longevity of DNA. Although it will deteriorate if exposed to sunlight, it can remain intact for centuries under proper conditions (Silverstein, 1996). Because DNA is so durable , investigators can reopen old cases to reexamine evidence. DNA from animals and plants can also be utilized in criminal forensics. One of the most common applications of this is the analysis of pet hair from a