DNA identifies a person because each individual's DNA is unique, except for identical twins. DNA, located in the cell's nucleus, contains a unique sequence of genetic information. Forensic scientists analyze specific segments of this DNA, known as DNA markers, to create a DNA profile. This profile acts like a genetic fingerprint, allowing for the identification of individuals.
Understanding DNA Profiles
A DNA profile is generated by analyzing variations in DNA sequences at multiple DNA marker locations. These variations are highly individual-specific, making it highly unlikely that two unrelated individuals will share the same DNA profile. The process involves:
- Sample Collection: Obtaining a biological sample (e.g., blood, saliva, hair) containing DNA.
- DNA Extraction: Isolating the DNA from the sample.
- DNA Amplification: Creating numerous copies of specific DNA marker regions using a process called Polymerase Chain Reaction (PCR).
- DNA Analysis: Determining the variations at each DNA marker using techniques like capillary electrophoresis.
- Profile Creation: Generating a unique profile based on the combination of variations at multiple DNA markers.
How DNA is Used for Identification
- Crime Scene Investigations: DNA from a crime scene (e.g., blood, semen, hair) can be compared to a suspect's DNA to determine if they were present at the scene.
- Missing Persons: DNA from unidentified remains can be compared to DNA from relatives to identify the deceased.
- Paternity Testing: DNA from a child and potential father are compared to establish paternity.
- Mass Disaster Victim Identification: DNA analysis is used to identify victims in mass disasters where bodies are fragmented or difficult to identify visually.
The power of DNA identification stems from the vast number of possible variations in DNA markers. The more markers analyzed, the more precise and reliable the identification. Databases like CODIS (Combined DNA Index System) store DNA profiles to aid in investigations and identifications. The accuracy of DNA identification is very high, contributing significantly to the justice system and humanitarian efforts.
As stated in the provided resources:
- "DNA determines each person's individual characteristics. An individual's DNA is unique except in identical twins." [Source: Understanding DNA Evidence: A Guide for Victim Service Providers]
- "Genetic identity testing involves identifying the patterns of genetic material that are unique to almost every individual." [Source: Discovery, development, and current applications of DNA identity testing]
- "Samples from crime scenes or suspects, usually obtained from blood, hair or body fluids, are analysed, resulting in a DNA profile which can be compared against..." [Source: Interpol - DNA]
