Genetic fingerprinting, also known as DNA fingerprinting or DNA profiling, works by analyzing highly variable regions of an individual's DNA to create a unique pattern that can be used for identification.
Here's a breakdown of the process:
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DNA Extraction: The process starts with obtaining a biological sample (e.g., blood, saliva, hair) and extracting the DNA from it.
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DNA Fragmentation: The extracted DNA is then cut into smaller fragments. This is often done using restriction enzymes, which are enzymes that recognize and cut DNA at specific sequences.
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Amplification (Optional): If the amount of DNA is limited, specific DNA regions of interest are amplified using a technique called Polymerase Chain Reaction (PCR). PCR creates millions of copies of the targeted DNA sequences.
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Separation by Size (Electrophoresis): The DNA fragments are separated based on their size using gel electrophoresis. The DNA fragments are loaded into a gel, and an electric current is applied. Smaller fragments move through the gel faster than larger fragments, creating a distinct banding pattern.
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Visualization: The separated DNA fragments are then visualized. Originally, this was done using radioactive probes. Now, fluorescent dyes are more commonly used. These dyes bind to the DNA and allow the banding pattern to be seen under UV light or other detection methods.
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Analysis and Interpretation: The resulting pattern of bands is unique to each individual (except identical twins). This pattern is then compared to other DNA samples to determine if there is a match.
Key Concepts:
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Short Tandem Repeats (STRs): Genetic fingerprinting commonly focuses on regions of DNA called STRs. These are short sequences of DNA that are repeated multiple times in a row, and the number of repeats varies greatly between individuals. This variation is what makes DNA fingerprinting so powerful.
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Polymorphism: The differences in the number of STR repeats between individuals are called polymorphisms. These polymorphisms are the basis for creating a unique DNA fingerprint.
In summary, genetic fingerprinting identifies individuals by analyzing the unique variations in their DNA sequence, particularly focusing on highly variable regions like STRs. The resulting pattern acts as a unique "fingerprint" that can be used for identification purposes.
