Unit-2 - Forensic Analysis Techniques: DNA profiling and its significance in identifying suspects and victims

Forensic Analysis Techniques: DNA profiling and its significance in identifying suspects and victims

DNA Profiling – Technique and Significance in Forensic Science

DNA profiling, also called DNA fingerprinting or DNA typing, is one of the most powerful forensic tools for identifying individuals with a high degree of certainty. It works on the principle that every person’s DNA is unique (except identical twins), and this uniqueness can be detected by analyzing specific regions of the genome.

DNA profiling is a scientific method used to identify individuals by examining unique patterns in their DNA. Although 99.9% of human DNA is the same for everyone, the remaining 0.1% contains variations, especially in regions called Short Tandem Repeats (STRs) that are different for each person.

Steps in DNA profiling:

1. Collection of Biological Samples
• Sources: blood, saliva, semen, hair roots, skin cells, bone, or tissue from a crime scene, victim, or suspect.
• Careful collection and preservation are essential to avoid contamination.
2. Extraction of DNA
• The DNA is separated from the cells in the sample using chemical or mechanical methods.
3. Amplification (PCR – Polymerase Chain Reaction)
• Even tiny amounts of DNA can be copied millions of times to make analysis possible.
4. Analysis of STRs (Short Tandem Repeats)
• STRs are short sequences of DNA that repeat in different numbers in different people.
• By comparing the number of repeats at several locations (loci) in the genome, a unique DNA profile is created.
5. Comparison with Known Samples
• The DNA profile from the evidence is compared with profiles from suspects, victims, or databases like CODIS (Combined DNA Index System).
• A match can link a person to a crime scene; a non-match can exclude them.