DNA (Deoxyribonucleic acid) is a molecule in the shape of a double helix. It is composed of 4 types of building blocks including Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). These single units of bases connect to form a chain of nucleic acid. Scientists have found that 99% of the DNA sequences are the same within the human species. These 99% of DNA are the codes that determine our height, eye and hair color, and even our intelligence. They do so by directing the production of proteins that carry out unique cellular functions or regulate the control of other genes so that they are switched on and off at appropriate times in the life of an organism. Only 1% of the DNA varies among individuals and that is what makes us unique. Scientists utilize this property to identify the relationship between individuals. They call these differences Short Tandem Repeats (STR). Variations in DNA sequence between individuals are termed "polymorphisms". These STR polymorphisms exist due to the different numbers of repeats that are found in a population. Sequences with the highest degree of polymorphism will be the most useful for DNA analysis in forensic cases and paternity testing.
DNA fingerprinting is a technique used to establish the genetic relationship between 2 individuals through examination of their DNA profiles. It is a valuable identification tool since DNA is the genetic material that we inherit from our parents and is unique for everyone. Interestingly, the same DNA materials are found in every cell in our body. This important characteristic makes DNA fingerprinting a widely used method in forensic science as it allows one to determine the relationship between a suspect and the DNA obtained from a crime scene.