DNA fingerprinting (also called DNA profiling or forensic genetics) is a technique employed by forensic scientists to assist in the identification of individuals or samples by their respective DNA profiles. Although more than 99.1% of the genome is the same throughout the human population, the remaining 0.9% of human DNA shows variations between individuals. These variable DNA sequences, termed polymorphic markers, can be used to both differentiate and correlate individuals. Alec Jeffreys, a geneticist at the University of Leicester in Britain, invented the first usable version of DNA fingerprinting in 1984. Few years later, a chemical company, Imperial Chemical Industries (ICI), launched the first kit commercially available. Forensic genetics is used in the legal field to solve civil cases like paternity tests and inheritance. It helps link the perpetrator to the crime scene in criminal cases where biological evidence, such as blood or hair, is found. It is also used to identify victims of mass disasters and missing persons using human remains. The availability of DNA profiling can help a body when traditional methods such as physical appearances, fingerprints or dental records have failed.
DNA is the genetic material that determines our traits, such as eye colour or hair type. Each person inherits half of their DNA from their mother and half from their father, resulting in unique combinations of genes and alleles. Humans have 23 pairs of chromosomes, which contain genes—specific parts of DNA that determine our characteristics. The unique combination of alleles you get from both parents creates your individual DNA profile. Even siblings, who share the same parents, have different combinations of alleles, making their DNA profiles different. Additionally, there are non-coding regions of DNA that don’t determine traits but still vary between people, contributing to the uniqueness of each profile.
The most common method used in DNA profiling is called Short Tandem Repeat (STR) analysis. STRs are specific areas of DNA that contain repeating sequences. We examine these regions to create a DNA profile. Each person has a different number of repeats in these regions, making the DNA profile of each individual unique.
For forensic DNA database, autosomal short tandem repeat (STR) markers, mitochondrial DNA (mtDNA) are currently being used for the purpose of identification. STR markers accounting for 3% of the human genome are highly variable in their repeat numbers. STR markers are widely known for their non-association with any of the gene expression as they are non-coding in nature. However, few recent studies have linked these non-coding sequences such as STRs with gene regulation via different mechanisms. This led to the speculation that, STR markers can also be explored for their usability in either biogeographic ancestry or phenotype prediction of an individual. In this regard, population data analysis revealed some unique population-specific alleles and genotypes in different populations. These studies suggested that, it is possible to infer biogeographical ancestry (BGA) from forensic STRs by using population-specific STR data as intelligence to guide enquiries.