Why DNA Profiling Is a Powerful Identification Tool
DNA profiling is a highly accurate method used to compare individuals based on their genetic makeup. It has revolutionized forensic science, paternity testing, and biological research. Although humans share more than 99% of their DNA, the remaining variation is enough to create a unique genetic pattern for nearly every individual. Understanding how this works is essential for IB Biology students exploring biotechnology and genetics.
The most common method relies on short tandem repeats (STRs)—sections of DNA where short sequences of bases repeat multiple times. Different people have different numbers of repeats at each STR location, making these sites ideal for comparison. STRs are scattered throughout the genome and vary greatly between individuals, even within families.
To analyze STRs, scientists first extract DNA from cells such as blood, hair, or saliva. They then use PCR to amplify specific STR regions, ensuring there is enough DNA for testing. Each STR location is targeted using primers that flank the repeat region, producing fragments of varying lengths depending on the number of repeats present.
Once amplified, the DNA fragments are separated using gel electrophoresis or capillary electrophoresis. These techniques sort fragments by size, creating a distinctive banding pattern or digital peak profile for each individual. Because STR lengths differ from person to person, the resulting pattern acts like a genetic “barcode.”
To compare individuals, scientists examine multiple STR sites—often 13 or more. A match across all tested STRs provides extremely strong evidence that two samples came from the same individual. The probability of two unrelated people sharing the same profile is astronomically low.
DNA profiling is especially valuable in forensic investigations. It can link suspects to crime scenes, identify missing persons, or exclude innocent individuals. In paternity testing, profiles from a child are compared to the alleged parent; shared alleles indicate a biological relationship.
Importantly, DNA profiling analyzes non-coding regions, meaning it does not reveal personal traits or medical information. This protects privacy while still enabling accurate identification.
FAQs
Why are STRs used instead of genes?
STRs vary greatly between individuals and do not affect traits, making them ideal for identification without revealing sensitive genetic information.
Can identical twins be distinguished using DNA profiling?
Standard STR profiling cannot distinguish identical twins because they share identical DNA sequences.
How accurate is DNA profiling?
When multiple STRs are analyzed, the probability of a coincidental match is extremely low, making DNA profiling highly reliable.
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