DNA Testing Basics

DNA testing is now being used in a variety of settings, including paternity testing, forensic (crime) DNA testing and genealogy testing.

DNA is substance in our cells that controls all of our biological traits, including things like eye and hair color. DNA is a very skinny string and made up of strands of 4 different nucleotides, which are most commonly referred to as A, T, G and C. Those letters stand for longer chemical names, but even the scientists use the letters when referring to a sequence of DNA. The nucleotides pair up, like rungs on a ladder. The ladder is twisted into a helix shape. The DNA helixes are then coiled and looped to form the chromosomes. Chromosomes come in pairs. Humans have 23 pairs of chromosome, 22 regular chromosome pairs and one pair of gender chromosomes that determine whether we are male or female.

The order of the nucleotides is referred to as genetic code. You will often see it written as GCCTAAGTTCAGGGT. A piece of DNA could be synthesized from this code alone. When DNA testing is performed, the DNA code is used to identify similar or identical pieces of DNA. Because the DNA code is passed from parent to child, it is easy to determine if a child belongs to one or both parents. This is why paternity testing has become so commonplace.

But DNA testing can look for much more than a maternal and paternal relationship with a child. Forensic DNA testing compares biological samples taken from crime scenes to determine if there is an exact DNA match to victims, witnesses and suspects. Although this science was not admissible several years ago, the technology has evolved and it is now widely accepted by the courts.

In addition to establishing paternity, DNA testing can be used to determine more distant family relationships. By comparing samples from several related individuals, a lab can determine if an individual is related to the family. This type of ancestral DNA testing is more accurate when the family members are closer in relationship to the person who is trying to establish the relationship.

Prenatal DNA testing is used to identify babies that are affected by genetic disorder such as Down's Syndrome. It can also accurately determine the gender of the unborn baby, which is of concern to many parents.

Scientists hope to uncover the code for a host of genetic disorders and then to find a way to prevent or correct them. The first step in this process was to map the entire human genome sequence. This was known as the Human Genome Project and DNA testing techniques made it possible.