Forensic Genetics

The role of genetics in forensic science is based greatly around the use of DNA (deoxyribonucleicacid), the twentieth century's greatest development. From Mendel's first pea plant projects, depicting the heriditary traits from parent to child, then to the recent release of the full human genome in 2001, DNA fingerprinting has enabled forensic science to reach an unpecendented level, not previously possible.

DNA Fingerprinting Anyone who knows about the basics of DNA will know this is one of the most precise methods of human identification. The pairs of bases (guanine, adenine, cytosine and thymine) are arranged in a unique pattern in each individual's DNA, creating the genetic 'identifier'. Furthermore, DNA's ladder like structure (in which rungs are created by two connecting bases) means that incomplete DNA strands (half a rung) can be replicated. Guanine always pairs up with cytosine to form a rung and likewise with adenine and thymine. Thus, if either one is present on one side of the ladder, the supplementing side can be easily predicted. With the average odds of 1 in 10 million people having the same genetic make-up (precision varies with different DNA samples and the extent of the DNA's purity upon finding), DNA databases are known to be a reliable source of a suspects conviction or acquittal.

The samples used to extract DNA may be, notoriously, as fine as a piece of hair or bloodstains left at the scene. They must be kept as clean and untouched as possible, to prevent sample contamination, leading eventually to being discreditted. Usually however, the samples will not be complete DNA and may only be extracts from a whole strand. One should understand that the majority of genetic information in our DNA is actually insignificant and does not contribute to what one looks like or behaves. However, this part (known as 'junk') is also what forensic scientists use to determine individuality. The incomplete samples of DNA will usually come from the junk and through a process known as the polymerase chain reaction (PCR), the short strand can be replicated to create an entire strand. The enzyme 'polymerase' acts as a catalyst to the replication of DNA, speeding up the process.

To be continued...